Global Positioning System 

Measurements on the Island of Hawaii. 

from 1987 to 1990 
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Global Positioning System 

Measurements on the Island of Hawaii 

from 1987 to 1990 

By John J. Dvorak, Arnold T. Okamura, Michael Lisowski, William H. Prescott, and 

Jerry L. Svarc 

U.S. GEOLOGICAL SURVEY BULLETIN 2092 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1994 
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary 

U.S. GEOLOGICAL SURVEY 

Gordon P. Eaton, Director 

For sale by 

U.S. Geological Survey, Map Distribution 

Box 25286, MS 306, Federal Center 

Denver, CO 80225 

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does 

not imply endorsement by the U.S. Government. 

Library of Congress Cataloging-in-Publication Data 

Global Positioning System measurements on the Island of Hawaii from 1987 to 1990 I by John J. Dvorak ... [et al.]. 

p. em.- (U.S. Geological Survey bulletin; 2092) 

Incudes bibliographical references. 

1. Earth movements-Hawaii-Kilauea Volcano Region-Measurement. 2. Volcanism-Hawaii-Kiluea Volcano. 3. Global 

Positioning System. L Dvorak, John (John J.) II. Series. 

QE75.B9 no. 2092 

[QE598.5.U6] 

557.3 s-dc20 94-13918 

[551.2'09969'1] CIP 
CONTENTS 

Abstract........................................................................................................................ 1 

Introduction .. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

History of ground movements on the island of Hawaii....................................... 2 

Limitations of conventional land-surveying techniques..................................... 3 

Brief description of the Global Positioning System................................................... 3 

Description of surveys .. .. ......... .. . . . ... . .. . . . ... ... ....... ... . ... . ..... ....... .. .. . . ..... ..... ......... .. .. ....... 4 

Goals of these surveys . . . . ..... .. .......... .. .. . ..... .. . . .. . . . .. ........... ......... ....... ..... ... . . ......... 4 

Survey dates and stations.................................................................................... 6 

Data analysis............................................................................................................... 6 

Procedure ........... .... ....... ... . .. . . . . .. . . . ....... .. ... . .. . .... ..... .. . ....... ... . ........ .............. .. .. . .... 6 

Selection of satellite orbits .. .. .. ... ....... ..... .... ..... .......... ......... .... .. . . . ... . ......... .. . . . . .... 8 

Sources..................................................................................................... 8 

Evaluation................................................................................................. 9 

Survey results . . . . .. . .. . . . . . .. . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . .. . . . . . . . .. . . . . . . . .. . . . . . . . . . . . . .. . . . . . 12 

Station coordinates .. .. ....... ...... ............ ... . ...... .............. ........ ..... .. . . . .. .. . ......... ... . .... 13 

Comparison of GPS and trilateration measurements ...... .. . .. . . . ........ ........... .. ... . ... 18 

Stable baselines.................................................................................................. 19 

Height of the geoid ... . .. . . ......... ..... ..... .... ...... .. . ... . . . . . .......... .... .. . . . ......... .. . ... . . . ........ 20 

Slow subsidence of the summit area of Kilauea volcano.................................... 22 

Seaward movement of the south flank of Kilauea volcano .... ... . . .. .. .. . . . . . .. .... ... . . .. 25 

Summit area of Mauna Loa volcano................................................................... 28 

Kealakekua fault system..................................................................................... 31 

GPS as a tool to study active volcanoes..................................................................... 31 

Acknowledgments .. . . . .. .. .... .. ... .. . ..... ......... .. ... .... .. . . . .. . . .. . . . ............ ... . . . . . ........... .. . . . ......... 31 

References .... .. ....... .. . .. ....... .. . .. . ... ..... ........ ........... .. . .. . .. ......... ... .. .. ......... ........ ... . . .. ...... .. . 31 

FIGURES 

1. Maps of the island of Hawaii, showing the five volcanoes and locations of the 47 sites surveyed using GPS...... 2 

2. The GlQbal Positioning System............................................................................................................................ 4 

3. Using GPS to make measurements of relative position....................................................................................... 4 

4. Location of GPS stations on Kilauea and Mauna Loa volcanoes .... ............. ......... .... ..................... .................... 5 

5. The sites occupied during each GPS survey........................................................................................................ 7 

6. Annual measurements of the baseline distance between KOKEE PARK, Kauai, and LYMAN2 in 

Hilo, Hawaii.......................................................................................................................................................... 11 

7. Comparison of the 1987 position of LYMAN2 determined by broadcast orbits, orbits calculated using 

tracking data from NGS, and orbits from NSWC.... ................ .. ................................................. .............. ......... .. 11 

8. Comparison of station positions using orbits calculated using tracking data from NGS and orbits from 

NSWC................................................................................................................................................................... 12 

9. Daily variations in computed station positions during the April 1987 survey.................................................... 12 

10. Comparison of trilateration and GPS measurements .. . . . . . . .. ... .. .......... .. .. . . . .. . . . . . . .. .. .. ... .. . . ... .. .. . . ......... ....... ....... .. .... 21 

11. The difference between trilateration and GPS measurements plotted as a function of baseline distance.......... 22 

12. Comparison of changes in line lengths measured by trilateration and GPS ....................................................... 22 

13. Measurements across six stable baselines on Hawaii.......................................................................................... 23 

14. Geoid heights across the island of Hawaii, relative to LYMAN2 in Hilo .......................................................... 25 

15. Slow subsidence of the summit area of Kilauea, indicated by results of leveling surveys................................ 26 

16. Slow subsidence and contraction of the summit area of Kilauea volcano, measured by GPS........................... 26 

III 
IV CONTENTS 

17. Horizontal displacement on Kilauea volcano and seismic activity between (1) April 1987 and 

August 1988 and (2) August 1989 and August 1990........................................................................................... 27 

18. Comparison of measured and computed horizontal displacement associated with the magnitude 6.1 

earthquake on June 26, 1989 ................................................................................................................................ 28 

19. Comparison of measured and computed vertical displacement associated with the magnitude 6.1 

earthquake on June 26, 1989 ................................................................................................................................ 28 

20. GPS measurements in the summit area of Mauna Loa volcano.......................................................................... 29 

21. GPS measurements along the southwest coast of Hawaii, the Kealakekua fault system................................... 30 

TABLES 

1. Summary of GPS surveys in Hawaii........................................................................................................................ 6 

2. Values of constant parameters................................................................................................................................... 8 

3. Coordinates of CIGNET stations.............................................................................................................................. 9 

4. Position of GPS station LYMAN2............................................................................................................................ 10 

5. Daily variations of each GPS survey........................................................................................................................ 13 

6. Average root-mean-square error of each GPS survey (5x) ...................................................................................... 13 

7. WGS-84 Cartesian coordinates................................................................................................................................. 13 

8. Latitude, longitude, and height................................................................................................................................. 16 

9. Coordinate differences between GPS surveys.......................................................................................................... 19 

10. Comparison of trilateration and GPS measurements................................................................................................ 20 

11. Model calculations for the June 1989 earthquake.................................................................................................... 29 
Global Positioning System Measurements on the 

Island of Hawa.ii from 1987 to 1990 

By John J. Dvorak, Arnold T. Okamura, Michael Lisowski, William H. Prescott, and Jerry L. Svarc 

ABSTRACT 

The Global Positioning System (GPS) is a satellite-based 

s_ystem that can be used to determine relative ground positions to a few centimeters or less over distances of tens to 

hundreds of kilometers. The system was used in Hawaii to 

measure the pattern of ground displacement associated with 

(1) the slow withdrawal of magma from the summit reservoir of Kilauea and (2) a magnitude 6.1 earthquake beneath 

the south flank of Kilauea on June 26, 1989. 

GPS surveys were conducted on the island of Hawaii in 

April 1987, August 1988, August 1989, and August 1990. 

Approximately 40 ground stations were occupied during 

eac~ survey. TI4100 radio receivers, which simultaneously 

recetve a P-code and radio signals on two frequencies from 

four ~ifferent satellites, were used during all surveys. Pcode 1s an encrypted time code from a satellite that allows 

unambiguous determination of satellite positions and empirical corrections for drift of each receiver-clock. Receipt 

~f two radio frequencies allows a correction for propagation delays caused by the ionosphere. 

We used satellite positions computed from orbits provided by the U.S. Naval Surface Weapons Center (NSWC). For 

our purpose, these positions were nearly the same as those 

computed from tracking data obtained from the worldwide 

system of GPS receivers operated by the National Geodetic 

Survey (NGS); the difference in relative ground positions 

on the island of Hawaii varied by a centimeter or less when 

we used orbits provided by NSWC or computed our own 

orbits from NGS tracking data. A similar comparison for the 

548-km-long line between the GPS-tracking station on 

Kauai (KOKEE PARK) and our reference station at the Hilo 

airport (LYMAN2) showed the difference was 128 mm or 

less (0.23 part per million). 

All measurements were processed using the Bernese softwa~e package. The internal consistency of each survey was 

~stlmated from the daily variation in computed station positiOns when the same baselines were measured on more than 

Manuscript approved for publication April 4, 1994. 

one day. These daily variations were about five times the 

standard errors computed using the Bernese package. The 

least consistent surveys were conducted in August 1988 and 

August 1989, when radio signals from a key satellite were 

unavailable. In these cases, daily observing sessions lasted 

less than 4.4 hours, and four satellites could be tracked 

simultaneously for only 20 minutes. During surveys in April 

1987 and August 1990, when daily observing sessions lasted up to 6.3 hours, the repeatability of station positions was 

20 mm for horizontal components and 49 mm for vertical 

components. These values are as much as a factor of two 

larger than values reported for surveys of similar baseline 

lengths conducted in California. The lower repeatability of 

our surveys may be the result of our shorter observing sessions and of the location of our surveys outside the dense 

network of GPS-tracking stations on North America that 

were used to compute satellite orbits. 

Our GPS measurements show that the summit area 

of Kilauea subsided at least 0.2 m between April 1987 and 

August 1990. The subsidence, which was indicated also by 

repeated leveling surveys, was probably related to continued eruption of the volcano. During the four years 

spanned by our surveys, Kilauea erupted about 0.3 km3 of 

lava; 10 percent of the erupted volume can be accounted 

for by net subsidence of the summit area. We suggest that 

the other 90 percent was supplied by a deeper source that 

had no significant influence on ground displacement measured by GPS or other geodetic techniques. 

The largest ground displacement recorded by GPS 

were associated with a magnitude 6.1 earthquake beneath 

the south flank of Kilauea on June 26, 1989. Horizontal 

displacements at sites located over the aftershock zone 

showed seaward displacement of the south flank of as 

much as 0.3 m. Subsidence of as much as 0.25 m occurred 

near the eastern edge of the aftershock zone. 

INTRODUCTION 

The attempt to provide accurate predictions of volcanic 

eruptions has benefited from the measurement of ground 
2 GLOBAL POSITIONING SYSTEM MEASUREMENTS ON THE ISLAND OF HAWAII FROM 1987 TO 1990 

displacement that results when magma moves up toward the 

ground surface. Though standard land-surveying techniques, such as leveling, triangulation and trilateration, have 

been used to record this displacement, these techniques require at least several days to complete and are restricted in 

the choice of survey sites. These limitations are partially 

overcome by a satellite-surveying technique that makes use 

of the Global Positioning System (GPS). 

GPS uses a set of satellites and mobile ground-based 

receivers to determine ground positions. Though this system is still being developed, measurements made during 

the last few years show that relative three-dimensional positions on a centimeter-scale can be determined across 

baselines that range from tens to hundreds of kilometers. 

The speed, accuracy, and versatility of GPS make it an 

·especially attractive as a tool to study active volcanoes. 

We began using GPS in April 1987 on the active 

volcanoes in Hawaii, in particular on Kilauea volcano 

(fig. 1), one of the most active and thoroughly studied volcanoes in the world. The existence of extensive and frequently measured geodetic networks on Kilauea allows a 

comparison to be made of the amount of ground displacement measured by GPS and by other techniques. 

HISTORY OF GROUND MOVEMENTS 

ON THE ISLAND OF HAWAII 

Thomas A. Jaggar, Jr., one of the pioneers of the 

study of active volcanoes, began daily tilt measurements 

in the summit area of Kilauea in 1913. After two decades 

of measurements, Jaggar concluded that magma accumulated slowly in a shallow reservoir beneath the summit 

area (Jaggar and Finch, 1929). The accumulation was interrupted when an eruption occurred along one of two radial rift zones, and magma drained rapidly from the 

summit reservoir. Ground displacement caused by several 

dozen cycles of slow filling, each ending by a rapid withdrawal of magma and usually a rift-zone eruption, has 

now been recorded using a wide variety of techniques. 

Beginning in the 1960s, these same techniques were extended to other areas of the island of Hawaii to search for 

other possible components of ground displacement. These 

efforts were quickly rewarded when measurements showed 

seaward displacement of the south flank of Kilauea, the 

portion of Kilauea that lies south of the two rift zones. The 

displacement was related to formation of new eruptive fissures (Swanson and others, 1976) and to a magnitude 7.2 

earthquake beneath the south flank (Lipman and others, 

1985). Measurements at adjacent Mauna Loa volcano 

showed gradual uplift, then rapid subsidence of the summit 

area associated with the 1984 eruption (Decker and others, 

1983; Lockwood and others, 1987). Other measurements on 

Kilauea revealed a secondary magma reservoir along the east 

rift wne (Jackson and others, 1975), a migration of uplift 

centers in the summit area (Fiske and Kinoshita, 1969), the 

size of dikes that fed the 1971 and 1983 eruptive fissures 

(Dvorak and others, 1984; Dvorak, 1990), and the growth rate 

of the 1983 eruptive fissure (Okamura and others, 1988). 

The rate and pattern of ground displacement of Kilauea 

have been used, along with studies of seismicity, gas emission, and petrology of erupted material, to propose a model 

Hawaiian Islands Hawaii 

A0 KAUAI 

~ ~AHU 

Honolulu ~~UI Hu 

~on of HAWAIIlii!!:o 

plate movement, • 

100 

~ 

km B 

9 cmlyr Hot spot 

GPS stations on Hawaii 

c 

• .. :~·· I 

_~A~ __ A~ _2f_!i[_W!_ 4_j 

50 km 

Contour -interval 300 m 

Figure 1. The island of Hawaii lies at southeast end of the 

Hawaiian island chain, over an anomaly in the mantle termed 

a hot spot (A). The hot spot supplies magma to the active 

volcanoes, where it is erupted either in one of the summit 

areas or along one of the long rift zones radial to each summit area, indicated in map C as broad shaded lines. Hawaii is 

composed of five volcanoes (B): Kohala is considered extinct; 

Mauna Kea and Hualalai last erupted 4,000 and 200 years 

ago, respectively; Mauna Loa last erupted in 1984; and 

Kilauea has been erupting since 1983. Most GPS stations, indicated as solid circles in map C, are located on Kilauea. Stations have also been located around the summit area and 

upper slopes of Mauna Loa and along the southwest coast of 

the island, the Kealakekua fault system. An enlargement of 

the area enclosed by the dashed rectangle in C is shown in 

figure 4. 
BRIEF DESCRIPTION OF THE GLOBAL POSITIONING SYSTEM 3 

for the way Kilauea works (Eaton and Murata, 1960; Wright 

and Fiske, 1971; Decker, 1987; Dvorak and others, 1992; 

Tilling and Dvorak, 1993). As magma rises from the mantle 

into the summit reservoir located a few kilometers beneath 

the summit area, the surface of the volcano rises and distends. 

Magma accumulation is usually gradual, causing tens to 

hundreds of millimeters of ground displacement in the summit area over a period of several months to a year. When 

magma moves laterally from the summit reservoir along a 

conduit beneath a rift zone, the summit area subsides rapidly, 

dropping several hundred millimeters within a few hours. 

A dike that feeds an eruption begins to grow upward from 

a depth of a few kilometers either from magma stored in 

the summit reservoir or stored beneath a rift zone. By the 

time the dike has breached the surface and an eruption ensues, 

the dike may be a few kilometers high, several kilometers 

long, and a meter or more wide. A dike widens the rift zone 

and compresses the adjacent portion of the flank. Repeated 

injection of magma as dikes and compression of the flank 

cannot continue indefinitely. Eventually, the compression is 

relieved as a large earthquake, and the south flank of Kilauea 

suddenly moves seaward (Swanson and others, 1976). 

LIMITATIONS OF CONVENTIONAL 

LAND-SURVEYING TECHNIQUES 

The three strategies used at Kilauea to measure 

ground displacement are designed to record changes in (1) 

elevation, using a standard leveling technique, (2) horizontal strain by making trilateration measurements, or (3) 

ground inclination, called tilt. 

The releveling of benchmarks to determine elevation 

changes is the best way to reveal a detailed pattern of vertical 

ground displacement if stations are closely spaced. Furthermore, vertical displacement of less than a part per million 

can be measured by using very simple equipment and field 

procedures (Dzurisin, 1992); a second-order leveling survey, 

which is usually achieved at Kilauea, has an accuracy of 

10 rnm over a distance of 25 km. Major limitations are 

that the distance between stations must be easy to traverse, 

which usually requires the existence of a drivable road, 

and that a survey requires a few weeks to complete. These 

two limitations have restricted the use of leveling surveys 

to only a few volcanoes. One happens to be Kilauea, because 

the summit area is accessible by paved roads. 

The second strategy makes use of electronic-distancemeasuring (EDM) instruments to measure changes in distance between pairs of benchmarks. Most EDM instruments 

now use a laser, which, depending on how the correction for 

atmospheric refraction is made, can be used to measure a 

horizontal distance to an accuracy of a few millimeters to a 

few centimeters over distances of 50 km or less. In order for 

these measurements to be made rapidly and over a broad 

area at Kilauea-rapid measurements are important because 

the surface of the volcano can move in several quick events 

in a month or less-temperature measurements of the atmosphere are made only at the two benchmarks, not over 

the entire path of the laser beam. Field tests show that 

endpoint temperature measurements limit the refraction correction to an accuracy of 3 or 4 parts per million (Decker 

and others, 1966), and so the distance between benchmarks 

separated by 10 km must change by more than 30 to 40 mm 

to be detected. Another disadvantage of trilateration measurements is that stations must be intervisible; thus, it is 

difficult to locate stations in rugged and steep terrain or in 

heavily forested areas, which are common around many 

volcanoes. To a degree, these limitations also apply to 

Kilauea. Few trilateration measurements have been made 

across the forested areas on the north flank and along portions of the east rift zone, and because of steep terrain, few 

measurements link activity along the rift zones and displacement of the south flank. 

Though many different techniques have been developed to measure changes in ground tilt, all techniques 

have the problem of being able to record ground displacement over a short baseline. The difficulty is reduced where 

tilt changes are determined by measuring elevation changes between benchmarks separated by a few tens of meters. 

This technique, often called the "dry-tilt" method, has 

been used to record tilt changes as small as a few microradians (Yamashita, 1992). Because many volcanoes have 

steep slopes, this technique has had limited use. A further 

limitation of the dry-tilt method is that benchmarks must 

be very stable: A vertical change of 0.1 mm over a baseline of 30 m indicates a tilt change of 3 microradians. 

In summary, the severest limitation of conventional 

land-surveying techniques is the choice of sites. Potential 

GPS stations, however, can be located almost anywhere, 

as long as a clear view of the sky is visible 20° above the 

horizon and the station is not near metal structures, such 

as buildings and wire fences. Furthermore, GPS measurements can be made in more severe weather conditions 

than conventional techniques, and the radio receivers can 

operate unattended for days to months. 

BRIEF DESCRIPTION OF THE 

GLOBAL POSITIONING SYSTEM 

The GPS was designed by the U.S. Department of Defense as a satellite-based navigational system for real-time 

military applications. Military users can use GPS to determine absolute positions to within a few meters. Because 

radio signals from the satellites are encrypted and altered 

intentionally, civilian users are limited to an accuracy of 

absolute positions of 100 m; however, radio signals received by two ground receivers operating in a differential 

mode can be combined to determine relative positions at 
4 GLOBAL POSITIONING SYSTEM MEASUREMENTS ON THE ISLAND OF HAWAII FROM 1987 TO 1990 

the centimeter-level over distances of tens to hundreds of 

kilometers. It is in the high-precision, differential mode that 

GPS becomes a tool to measure surface displacement of 

geophysical interest. 

Radio signals are transmitted from a constellation of 

satellites in 20,000-km-high orbits, giving an orbital period of 12 hours, and inclined 60° to the equator (fig. 2). 

Each satellite transmits on two L-band frequencies (L1 on 

1575.42 MHz and L2 on 1227.60 MHz), which correspond to wavelengths of 0.19 m for L1 and 0.24 m for L2. 

Meter-level positioning is obtained by military users by receiving a special ranging code transmitted by each satellite, which enables the user to determine the distance to 

three or more satellites whose orbital positions are already 

known. Because errors are still present in satellite and receiver clocks, the range estimates are called pseudoranges, 

to distinguish them from the actual range distances between the satellites and a ground receiver. 

In the differential mode, in which each pair of ground 

receivers observes simultaneously four or more satellites 

(fig. 3), we use pseudorange measurements to compute empirical corrections of drift of the receiver clocks. A high 

precision in positioning is obtained because of the submeter 

wavelength of the L-band signals and the use of carrier-phase 

measurements on the radio signals. By using phase measurements, the resulting distance between each satellite and 

receiver pair is ambiguous by an integer number of wavelengths. Because a large number of phase measurements is 

made, the phase ambiguities can be resolved, if we keep track 

of the number of cycles that occur between phase measurements. The use of two radio frequencies is needed to correct 

for the time delay as the radio signals pass through the 

ionosphere. Also there is a need to recompute satellite positions from observations taken from widely spaced sites when 

our surveys were conducted, because the satellite positions 

broadcast by the satellites at the time of the survey are 

Figure 2. GPS consists of a network of NAVSTAR satellites in 20,000-km-high orbits. At this height, each satellite 

has an orbital period of about 12 hours. The future operation of 21 satellites will give 24-hour coverage over most 

areas of the world. 

extrapolations and may be further reduced in accuracy by the 

Department of Defense by a procedure known as selective 

availability. Additional details of how phase measurements 

are used to determine ground positions, as well as a more 

complete description of GPS, are given in Wells and others 

( 1986) and Dixon ( 1991 ). 

DESCRIPTION OF SURVEYS 

Four GPS surveys were conducted on the island of 

Hawaii between April 1987 and August 1990 using dual 

radio-frequency TI4100 receivers. Forty-seven sites were 

occupied (figs. 1 and 4), of which many were occupied for 

only one day during each survey. 

GOALS OF THESE SURVEYS 

Frequent volcanic and seismic activity at Kilauea has 

made this volcano a proving ground for new techniques 

designed to measure magmatic activity in the upper crust. 

We had the following goals for using GPS in Hawaii. 

• Evaluate GPS as a technique to measure slow 

crustal displacement in the mid-Paci.fic.-Many GPS surveys have been conducted on large continental land masses, often at latitudes of the continental U.S. or higher, such 

as Alaska (Beutler and others, 1987) and California and 

the Rocky Mountain States (Davis and others, 1989). The 

island of Hawaii is a different environment because it is 

located at low latitudes and is surrounded by ocean. High 

humidity may limit the accuracy of GPS in Hawaii and 

elsewhere in the subtropics and tropics. 

Figure 3. Though GPS was originally designed to determine absolute positions at meter level, station locations 

can be determined to centimeter level by making relative 

measurements between pairs of ground-based receivers. 

Each receiver records signals from the same subset of 

NAVSTAR satellites. Generally, four or more satellites 

must be observed simultaneously to determine three-dimensional position of each receiver and to make an empirical correction of drift of each receiver clock. 
DESCRIPTION OF SURVEYS 5 

• Compare measurements made using GPS and conventional land-surveying techniques.-Several decades of 

measurements of ground displacement have been made in 

many dynamic regions of the world, especially along fault 

systems and volcanic chains. Before GPS can take the role 

as the primary means to make these measurements, simultaneous measurements must be made using both GPS and 

established techniques to understand the peculiarities of 

old and new techniques and to test that the same rates of 

ground displacement are measured by both techniques. 

• Carry out the initial Hawaiian surveys in the summit area and along the south flank of Kilauea, where the 

largest ground displacement is expected. -For more than 

three decades, intensive land surveys of Kilauea have 

identified several major components of ground displacement. We concentrated our initial effort in the summit area 

and along the south flank because these areas have had the 

largest amount and highest rates of ground displacement 

and are easily accessible. Thus, they are the most likely 

places for us to measure displacement. 

• Extend later surveys to areas where conventional landsurveying techniques are difficult to conduct (the summit 

area and upper slopes of Mauna Loa and along the 

Kealakekua fault system).-Topography has limited, or prevented, the use of conventional techniques in two areas of 

special interest: the summit area and upper slopes of Mauna 

Loa and along the Kealakekua fault system on the southwest coast of the island. While Mauna Loa does not erupt as 

frequently as Kilauea, eruptions of Mauna Loa are usually 

more voluminous, by a factor of 10 (Macdonald and others, 

1983), which suggests a larger magma reservoir associated 

with Mauna Loa. The remoteness of Mauna Loa makes it 

difficult to repeat leveling or trilateration measurements. 

Much is known about how Kilauea works, but infrequent 

eruptions of Mauna Loa have left a gap in a general understanding about Hawaiian volcanoes. The Kealakekua fault 

system offers an analogue to the Hilina fault system along 

the south flank of Kilauea, where two magnitude >6.0 earthquakes have occurred since 1975. During the last 40 years, 

three damaging earthquakes, all believed to be greater than 

magnitude 6.0, occurred along the Keala\ekua fault system. 

Furthermore, the earthquake risk has increased greatly 

along the west coast of Hawaii because of a rapid urban 

growth. 

20 Ian 

Contour interval 300 m 

Figure 4. Most GPS stations are located on Kilauea, the most active Hawailian volcano. Kilauea has been erupting along the east rift 

zone near KALALUA since 1983. The broad shaded lines are rift zones of Killauea and the adjacent volcano Mauna Loa. 
6 GLOBAL POSITIONING SYSTEM MEASUREMENTS ON THE ISLAND OF HAWAII FROM 1987 TO 1990 

SURVEY DATES AND STATIONS 

A summary of the four GPS surveys is given in 

table 1. Each survey lasted 3 to 6 weeks. Because a complete set of satellites was not yet in operation at the time 

we conducted our surveys, our observing sessions were restricted to a duration of 6 hours or less and to time of day, 

which depended on the time of year of each survey. The 

first three surveys used only so-called "Block I" satellites. 

The last survey used Block I satellites as well as three 

"Block II" satellites, which have more precise clocks than 

Block I but may be subjected to "selective availability," 

meaning broadcast ephemerides, clock epochs, and clock 

frequencies may be altered. 

The stations occupied by each survey and survey 

dates are shown in figure 5. Station names and coordinates 

will be presented later in the section "Survey Results." 

Each receiver recorded data on magnetic cassette 

tape: a pseudorange and a phase measurement were recorded every 30 seconds for both L 1- and L2-radio signals. 

At the end of an observing session, data were transferred 

from a tape onto two different Macintosh computer diskettes. At the end of a survey, one set of diskettes and 

data sheets, which recorded station name and antenna 

height and listed when satellites were observed, was sent 

to Menlo Park. 

When available, tracking data from the Cooperative 

International GPS Network (CIGNET) was obtained from 

the National Geodetic Survey (Chin, 1992), as well as data 

in 1987 from a GPS receiver operated by the University of 

Texas at Austin (D. Carroll, oral commun., 1989) 

DATA ANALYSIS 

Except for the choice of satellite orbits, our procedure to process data followed that outlined by Davis and 

others (1989), using the Bemese software package developed by Beutler and others (1987). 

PROCEDURE 

The first step in processing was to make an empirical 

correction for drift of each receiver clock. The correction 

used pseudorange measurements to compute an initial time 

offset and a fifth-degree polynomial for each receiver on 

each day. This correction probably introduces no more than 

a 1-mm bias in station positions because we used doubledifference values of our phase measurements (Beutler and 

others, 1987). (No pseudorange measurements from satellite 8 were used because the quartz clock on this satellite 

was too inaccurate to be used to compute receiver-clock 

corrections. Some Block I satellites use the more accurate 

rubidium clocks; the other Block I and all Block II satellites use the highly accurate cesium clocks.) 

For each observing session, single-difference values of 

phase measurements were computed for pairs of stations. 

Whenever possible, we used the station LYMAN2, located 

at the Hilo airport, as one station to compute single-difference values so that we would have common baselines year 

after year. For those days during the 1987 and 1988 surveys when LYMAN2 was not occupied, another reference 

station was chosen. The use of stations other than LYMAN2 is indicated in the lists of station coordinates. 

Double-difference values of phase measurements were 

computed and used to identify integer cycle slips and bad 

points. Orbits computed from parameters provided by 

NSWC were used in the identification. First, the differences 

of L 1-phase measurements were examined, then L2. When 

no more cycle slips or bad points could be detected either 

automatically by the program or visually by the operator, 

double differences were computed for L3, a linear combination of L 1 and L2, and examined for integer cycle slips. 

Table 1. Summary of GPS surveys in Hawaii. 

Number of Duration of 

Survey dates Type of stations observing Satellites observed receivers session occupied (hours) 

Mar. 31 to Apr. 29, 1987 TI4100 37 5.1 3, 6, 9, 11, 12, 13 

Aug. 12 to Sept. 2, 1988 TI4100 35 6.0* 3, 6, 9*, 11, 12, 13 

Aug. 8 to Aug 25, 1989 TI4100 44 4.8t 3, 6, 9t, 11, 12, 13 

July 31 to Aug. 17, 1990 TI4100 35 6.3 3, 6, 9, 12, 16, 18,20 

*Satellite 9 was not usable from Aug. 17 to Aug. 30, 1988. During these dates, observing sessions were 

reduced to 4.2 hours. 

tsatellitc 9 was not usable from Aug. 17 to Aug. 22, 1989. During these dates, observing sessions were 

reduced to 4.4 hours. 
DATA ANALYSIS 7 

The next step was to compute station positions and 

possibly new satellite orbits if tracking data from CIGNET 

(Cooperative International GPS Network) were included. 

In these computations, we used the constant parameters 

listed in table 2, as well as measurements of the Earth's 

orientation and theoretical predictions of solid Earth tides. 

To minimize multipath error, we required elevation angles 

of satellites to be 20° or higher (Dixon, 1991). 

A 

c 

)#fi#"". 

i 

Once satellite orbits were selected, computation of a 

station position relative to the fixed position of LYMAN2 

was a two-step process. The first step attempted to compute integer phase-cycle ambiguities from wide-lane values of the phase measurements, the so-called L5 phase 

values. Resolution of the phase ambiguity improves the 

horizontal position of a station, but has a slight effect on 

the vertical position (Dixon and others, 1991). Generally, 

B 

D 

Figure 5. Stations occupied during each of the four annual GPS surveys. Rift zones indicated by shaded lines radial to the summit 

areas of each volcano. Stations names are shown in figures 1 and 4. WGS-84 station coordinates are listed in table 7. A, March 30 

to April29, 1987; B, August 12 to September 3, 1988; C, August 8 to 25, 1989; D, July 31 to August 17, 1990. 
8 GLOBAL POSITIONING SYSTEM MEASUREMENTS ON THE ISLAND OF HAWAII FROM 1987 TO 1990 

Table 2. Values of constant parameters. 

Constant Value 

Physical constants: 

Velocity of light---------------------------------------

(Gravity constant) x (Earth's mass)----------------

(Gravity constant) x (Sun's mass) -----------------

(Gravity constant) x (Moon's mass)---------------

299792458 m/s 

Reference ellipsoid: 

Equatorial radius of Earth---------------------------

Flattening of Earth------------------------------------

Angular velocity of Earth ---------------------------

Eccentricity of TI41 00 antenna: 

0.39860044 x 1015 m3/s2 

1.3271250 x 1020 m3/s2 

9027890 x 1012 m3/s2 

6378137 m 

1/298.257222 

7292115.1467 X 10-ll radians/s 

L 1-phase center --------------------------------------- 0.227 m above the base of the preamp 

L2-phase center --------------------------------------- 0.212 

Satellite antenna offsets: 

Block I satellites 3, 6, 9, 12, and 13 --------------- X = 0.21 m Y = 0.00 m Z = 0.854 m 

Block II satellites 16, 18, 19 and 20--------------- X = 0.2794 m Y= 0.00 m Z = 1.0229 m 

we had good success in computing ambiguities, because 

most of our baselines were less 100 km. 

The second step was to calculate the L 1- and L2-

ambiguities using the values from the L5 solution, then to 

compute final station positions by incorporating a model 

for the troposphere. The ionospheric delay was eliminated 

by a linear combination of the L1- and L2-phase measurements and the L1- and L2-carrier frequencies (Wells 

and others, 1986). Radio waves are nondispersive in the 

troposphere, so the tropospheric delay was determined by 

computing a single-parameter, zenith-delay model and by 

using an azimuthal-independent mapping function to compute the delay of any elevation angle (Davis and others, 

1989). The following values at the height of the reference 

ellipsoid were used to compute the tropospheric delay: 

temperature=18°C, pressure=l013.5 millibars, and 50 percent humidity. This is the so-called "dry" correction, 

which assumes the troposphere is in hydrostatic equilibrium. A significant nonhydrostatic component may be 

caused by variations in content of water vapor, especially 

at the low subtropical latitudes of Hawaii. This problem 

is amplified on the island of Hawaii because a wide range 

of climatic conditions exists both laterally across the island (wet-windward versus dry-leeward sides) and over 

the 4-km elevation change between sea level and the summit areas of Mauna Loa and Mauna Kea. A correction for 

a nonhydrostatic component, the so-called "wet" correction, can be made if simultaneous measurements are made 

of water-vapor content during a GPS survey (Ware and 

others, 1986); however, water-vapor measurements are expensive and were not made in Hawaii. The result is probably a larger uncertainty of station positions for surveys 

conducted in the subtropics and tropics (Dixon and others, 

1991). 

SELECTION OF SATELLITE ORBITS 

GPS can be used to determine precise station positions if satellite positions are well known. For example, at 

a distance of 20,000 km, a satellite position must be 

known to within a few meters to attain centimeter-level 

accuracy in ground position across a 100-km baseline. 

This requires careful evaluation of the quality of orbits, 

which we evaluated by measuring changes along presumed stable baselines. 

SOURCES 

We considered three sources of satellite orbits: (1) 

positions broadcast by the satellites at the time of each 

survey, (2) orbits provided by the Naval Surface Weapons 

Center (NSWC) and (3) our own improved orbits using 

tracking data supplied by National Geodetic Survey from 

CIGNET. 

Both L 1- and L2-radio signals are modulated with a data 

stream that includes an orbital ephemeris of each satellite. 

Each ephemeris, which is broadcast on the hour, consists 

of the six osculating elements that uniquely define a position in space. A broadcast ephemeris is a predicted satellite 

trajectory computed from about one week of data collected 

from GPS stations operated by the Department of Defense 

(Wells and others, 1986). A new ephemeris is sent to a 

satellite at least once a day, though 6-hour updates are sent 

occasionally. Because these broadcast ephemerides are predicted satellite orbits, they are not adequate to determine 

precise ground positions, except for short baselines-that 

is, baselines less than 15 km in length. For this reason, we 

used broadcast ephemerides only to compute approximate 
DATA ANALYSIS 9 

Table 3. Coordinates of CIGNET stations. 

[Values provided by National Geodetic Survey (Chin, 1992, and written communication)] 

X 

April 1987: 

Austin, Tex. -743773.949 

Kokee Park, Ha. -5543817.052 

Mojave, Calif. -2356214.416 

Westford, Mass. 1492233.223 

August 1988: 

Kokee Park, Ha. -5543818.046 

Mojave, Calif. -2356214.438 

Richmond, Fla. 961318.469 

Westford, Mass. 1492233.228 

August 1989: 

Kokee Park, Ha. -5543818.046 

Mojave, Calif. -2356215.619 

Richmond, Fla. 961319.516 

Westford, Mass. 1492233.301 

station positions, which we can compare with a final station position computed using other satellite orbits if that 

station position deviated from our other estimates. In this 

way, we identified possible problems that occurred in computing our own orbits or in orbits obtained from NSWC. 

Precise satellite ephemerides are provided by NSWC 

several weeks after data has been received at a worldwide 

network of nine or more tracking stations. We use the 

NSWC ephemerides to compute satellite positions by 

straightforward integration, taking into account gravitational attraction of Earth, Sun, and Moon; a tenth-order 

and -degree model of Earth's gravitational field, called 

GEMlO (Lerch and others, 1979); solar radiation pressure; 

and a force on a satellite called the y-bias factor, which 

presumably is caused by thermal radiation of the satellite 

or misaligned solar panels (Schultz and others, 1990). The 

resultant integration, which is performed over an 8- to 56-

hour period, depending on the number of successive days 

a station was occupied, is used to compute a new set of 

osculating elements and a single parameter for solar radiation pressure and another parameter for they-bias factor. 

As a third source, we computed our own improved orbits 

using data collected by CIGNET tracking stations. Type of 

receiver and location and type of antenna often changed 

during the years of our four surveys (Chin, 1992). As a 

result, different coordinates and different combinations of 

CIGNET stations were used during our first three surveys 

(table 3). (No orbits were computed for the last survey 

because the receiver at Kokee Park, Kauai, did not track 

satellites at the same time of day that our 1990 survey was 

conducted.) Most station coordinates listed in table 3, taken 

from a list of station coordinates and offsets listed in Chin 

( 1992), are the positions of the L 1-phase center expressed 

in the World Geodetic System 1984 (WGS-84), a terrestrial 

Earth-centered reference frame tied to the inertial coordinate system of the satellites (Wells and others, 1986). (In 

y z Receiver 

-5460643.710 3200347.492 TI4100 

-2054588.402 2387854.185 Tl4100 

-4646733.924 3668460.609 Tl4100 

-4458091.535 4296045.911 TI4100 

-2054583.269 2387857.553 Tl4100 

-4646733.930 3668460.620 Tl4100 

-5674057.739 2740565.215 TI4100 

-4458091.550 4296045.925 TI4100 

-2054583.269 2387857.553 Tl4100 

-4646736.395 3668456.424 Mini Mac 

-5674075.349 2740538.919 MiniMac 

-4458088.267 4296047.992 MiniMac 

WGS-84, the X-axis passes through the intersection of the 

Greenwich meridian and the equatorial plane; the Z-axis 

passes through the average position of Earth's rotational 

pole for the 1984 epoch; and the Y-axis is orthogonal to the 

other two axes so that a right -handed coordinate system is 

formed.) The exceptions were the 1987 coordinates of Austin and Kokee Park. The station coordinate for Austin was 

provided by M. Chin (written commun., 1989) from measurements made in January 1987. From March 28 to April 

12, 1987, the GPS antenna at Kokee Park was at a temporary location at the WVRM monument (M. Chin, written 

commun., 1989). We have compared all 1987 coordinates 

obtained from NGS and coordinates in a reference frame 

called SV5 provided by M. Murray (written commun., 

1990). TheY- and Z-coordinates of the NGS and SV5 reference frames are all within 0.2 m. The X-coordinates are 

biased an average of 0.371 m; after subtraction of this average value, the X-coordinates of all four stations listed in 

table 3 for 1987 are within 0.034 m for the two reference 

frames. Baselines computed with broadcast and precise 

ephemerides show the latter to be more accurate (such as, 

Remondi and Hofmann-Wellenhof, 1990) because the precise ephemerides were computed from actual tracking of 

the satellites and, unlike the broadcast ephemerides, were 

not a prediction of satellite positions. We computed similar 

three-dimensional positions of baselines using satellite orbits provided by NSWC and orbits computed by ourselves 

from CIGNET tracking data. As will be shown in the next 

subsection, these positions were offset 0.3 m from positions 

computed from broadcast orbits. 

EVALUATION 

We evaluated satellite orbits three ways: (1) the ability 

to determine the three-dimensional position of the station 
10 GLOBAL POSITIONING SYSTEM MEASUREMENTS ON THE ISLAND OF HAWAII FROM 1987 TO 1990 

LYMAN2 relative to KOKEE PARK, both by a comparison of annual determinations and during several single-day 

measurements during the 1987 surveys, (2) the variation in 

computed station positions using NSWC orbits and our 

own improved orbits, and (3) daily variations in station 

positions computed during each survey. A fourth means, 

which will be presented in the next section, compared annual determinations of station positions across what we expect are stable baselines on the island of Hawaii. 

Annual determinations of the position of LYMAN2 

are listed in table 4, using either NSWC orbits or our improved orbits and expressed in WGS-84. The values 

shown in table 4 were the result of multiday calculations. 

For 1987, the values were the average of two multi day 

determinations, from April 1 to 4 and from April 5 to 8. 

For 1988, the values determined from NSWC orbits were 

from April 13 to 16, from April 19 to 20, from April 24 to 

26, and from April 28 to 31; the values determined from 

our computed orbits using CIGNET data were calculated 

from April 13 to 16. For 1989, only values determined 

from NSWC orbits are given, averaged from values determined from April 8 to 11 and from April 23 to 25; the loss 

of satellite 9 in August 1989 prevented us from computing 

an improved orbit. No positions for LYMAN2 were deterTable 4. Position of GPS station LYMAN2. 

April 1987 

NSWC orbits 

Calculated orbits 

August 1988 

NSWC orbits 

Calculated orbits 

August 1989 

NSWC orbits 

Largest variation 

April1987 

NSWC orbits 

Calculated orbits 

Difference 

August 1988 

NSWC orbits 

Calculated orbits 

Difference 

19° 43' 

19 43 

19° 43' 

19 43 

X 

-5445971.060 m 

-5445971.143 

-5445971.112 

-5445971.082 

-5445971.105 

0.083 m 

Latitude 

21.90783" 

21.90581 

0.062 m 

21.90519" 

21.90929 

0.126m 

-155° 

-155 

-155° 

-155 

mined for 1990 because the Trimble GPS receiver at 

KOKEE PARK did not track simultaneously the same satellites we were tracking on the island of Hawaii. 

The bottom of table 4 lists a conversion of WGS-84 

coordinates to latitude, longitude, and height above a reference ellipsoid. Also given is the baseline distance between LYMAN2 and the 1987 position of KOKEE PARK. 

The largest variations of the east-west and vertical components are about 0.1 ppm for the 548-km-long line between 

KOKEE PARK and LYMAN2; the variation of the northsouth component is 0.26 ppm. In 1987 and 1988, NSWCderived positions and our improved-orbit positions are 

within several centimeters for longitude and height, but 

unexplainably high for latitude. The annual determinations 

of the baseline length are shown in figure 6. 

For 1987 data, we also computed the position of LYMAN2 

from single-day data to check the amount of daily scatter. The 

results of our single-day analyses are compared with the 

multi day values in figure 7. Each symbol represents a singleday value of each component relative to the average value 

determined from multiday inversions using NSWC orbits. 

For comparison, we also show the average values determined 

from multiday inversions using our improved orbits and 

broadcast orbits. As reported by many researchers, such as 

y z 

-2533159.910 m 2138839.199 m 

-2533159.923 2138839.162 

-2533159.895 2138839.127 

-233159.900 2138839.252 

-2533159.915 2138839.110 

0.028 m 0.142 m 

Longitude Height1 Distance2 

3' 17.26675" 26.030 m 548281.852 m 

3 17.26755 26.093 548281.866 

0.029 m 0.063 m 0.014m 

3' 17.26798" 26.044 m 548281.863 m 

3 17.26739 26.063 548281.816 

0.017 m 0.019 m 0.047 m 

August 1989 

NSWC orbits 19° 43' 21.90465" -155° 3' 17.26726" 26.040 m 548281.890 m 

Largest variation 0.00318" 

0.143 m 

0.26 ppm3 

1 Height above reference ellipsoid. 2Distance between LYMAN2 and the 1987 position of KOKEE PARK, Ha. 

3Based on the 548-km distance between KOKEE PARK and LYMAN2. 

0.00123" 0.063 m 0.074 m 

0.036 m 

0.07 ppm3 0.11 ppm3 0.14 ppm3 
DATA ANALYSIS 11 

Remondi and Hofmann-Wellenhof (1990), similar station 

positions are computed using orbits derived from actual 

tracking data, as opposed to the broadcast orbits, which are 

predicted satellite positions and which have larger biases. 

Within the daily scatter shown in figure 6, NSWC and our 

improved orbits yield the same position for LYMAN2-that 

is, a position within 0.2 ppm or less. 

For 1987 data, we compared station positions on the island of Hawaii determined from NSWC and our improved 

orbits. In this comparison, we computed improved orbits for 

only the first two weeks of the survey, from March 31 to 

April 11, when a GPS station was operated at KOKEE 

PARK. For these two weeks, 21 comparisons were possible, 

using baseline lengths that varied from 11 to 108 km (fig. 8). 

If we include all baselines, the apparent changes in north/ 

south and east/west positions both have root-mean-square 

values of 5 mm. If we include only baselines shorter than 80 

km, the root-mean-square values were 2 and 3 mm for 

north/south and east/west positions, respectively. (The two 

baselines longer than 80 km were across the entire island, 

LYMAN2 to HP6 and LYMAN2 to MILOLII.) The rootmean-square value of vertical positions was 27 mm for all 

baselines, 12 mm for baselines shorter than 80 km. In summary, for stations on the island of Hawaii, the inversion 

scheme in the Bemese software using either NSWC orbits 

or our improved orbits from CIGNET tracking data yields 

horizontal positions to a centimeter or less and vertical positions to within five centimeters. We could not always compute an improved orbit because the CIGNET tracking 

stations did not always track the same satellites as we did 

during our surveys, especially when satellite 9 was unavailable during the 1988 and 1989 surveys. Orbits were always 

available from NSWC, so NSWC orbits were used to process all four Hawaiian GPS surveys. The remaining results in 

this report were derived solely by using NSWC orbits. 

Because the duration of daily observing sessions varied 

from 4.2 to 6.3 hours and because we lost satellite 9 midway 

through the 1988 and 1989 surveys (table 1 ), we must use 

an independent means to estimate the accuracy of each survey. This was done by computing root-mean-square values 

Largest variation: 0.038 m, 

0.07 parts per million 

0.5 --,r-----------------------, north-south -- NSWC orbits 

---- Calculated orbits 

·-------- Broadcast orbits 

-----------------------------o----------------------------------------

---o----

1 2 3 4 5 6 7 

April1987 

-----------------------------------0 -----------------------------------

---6-------cr--cr--

1 2 3 4 5 6 7 

April1987 

1 2 3 4 5 6 7 

April1987 

Figure 7. Comparison of daily and multiday determinations of 

the position of LYMAN2. The three components of position are 

shown with respect to the average position of LYMAN2 determined from NSWC orbits. Daily determinations are shown as 

symbols. 

~ Figure 6. Annual measurements of the distance between KOKEE PARK and LYMAN2. Largest variation 

was 0.038 mm, which, for this 548-km-long line, corresponds to 0.07 parts per million. 
12 GLOBAL POSITIONING SYSTEM MEASUREMENTS ON THE ISLAND OF HAWAII FROM 1987 TO 1990 

E 

E 

north/south RMS =5 mm (2 mm) 50~------~--~--~~---------------

"' - D D ""0 u ... u -u c 

a) -50~--------~-----------~--------r-----------------------~ I I I I I 

~ 0 20 40 60 80 100 

Baseline length, km 

east/west RMS = 5 mm (3 mm) 

m 

..c. 

0 

(ij 50~--------------------~----------~~------------------------------------------

0 

............. n ~ nO 0 0 ,.., V'-' ."" 

E 

0 

-~ 0~-o~r---g_~~~--~----------~------~ 

0 

:I: 

-50T------r----~------~----~------~ I I I I I 

0 20 40 60 80 100 

Baseline length, km 

200~----------------------------------

vertical RMS = 27 mm (12 mm) 

100-

E 

E 

of 

C) 

c: !J.a 6. 

m A 0 AA A ..c. 

0 -ag X c: 6. .Q 

«i 

> CD 

w_1 oo 

-200;-----------~r-----------~~-------~.-------.-------T--~ 

0 20 40 60 80 1 00 

Baseline length, km 

Figure 8. Differences in station positions determined using NSWC 

orbits and orbits calculated using tracking data from CIGNET. At 

top of each diagram is the root-mean-square value for all measurements; the numbers in parentheses are root-mean-square values for 

baselines shorter than 80 km. 

for horizontal and vertical components from the daily variation for baselines measured more than once during a survey. 

For the 1987 survey, repeated measurements were made of 

21 baselines. The apparent changes in station positions are 

shown in figure 9. The north/south and east/west components had root-mean-square values of 8 and 19 mm, respectively. The vertical component was 49 mm. These values are 

probably too pessimistic because they are based on single 

observing sessions. Some final station positions, to be given 

in the next section, are based on multiday analyses, which 

are more accurate than single-day analyses (for example, 

see Davis and others, 1989). The repeatability of each survey is listed in table 5, which is based on apparent changes 

in station positions for baselines repeated during a survey. 

The Bernese software computes a standard error for each 

of the three components of position. Davis and others 

(1989, p. 13,639) found that these standard errors "were too 

50 

D c 0 CCn c DC - , ,.., 

E D Du u D lJ 

E north/south RMS=Smm 

a) -50 I I I I 

C) 

c: 0 20 40 60 80 100 m 

..c. Baseline length, km 0 50 (ij 

E 0 0 0 oo 0 0 0 00 0 0 N - -~ (jO 0~ "" 0 0 

:I: 0 0 east/west RMS = 19 mm -50 I I I I 

0 20 40 60 80 100 

Baseline length, km 

200 

vertical RMS=49mm 

E 100 tJ. 

E 

a) !PtJ.!J. 

tJ. 6.6. tJ. C) 

c: 6. 

m 6. ..c. 0 A 6. 

0 A L\ 

c: 

0 6. 6. 6. 

~ 6. 

> CD 

w_1 oo . 

-200 ;-----------~.r------~.-------~.-------------.-------------~ 

0 20 40 60 80 100 

Baseline length, km 

Figure 9. Daily variations in computed station positions using 

NSWC orbits. The root-mean-square value for each component 

is given in each diagram. 

small by a factor of 3 to 5 to explain long-term variations." 

We arrived at a similar conclusion when we compared 

standard errors and daily variations for each survey listed in 

table 5. To illustrate, for each survey we computed the average standard error of each component and multiplied the 

result by five. The factor of five increased the standard 

errors to about the same values determined from our analysis of daily variations (compare tables 5 and 6). Later in 

this paper, where we report specific uncertainties of a station position, those uncertainties were determined by multiplying the standard error of each component by five. 

SURVEY RESULTS 

In this section, the position of each station for each 

annual survey is given in WGS-84 coordinates and in latitude, longitude, and height. Some coordinates are used to 
Table 5. Daily variations of each GPS survey. 

Survey 

April1987 

August 1988 

August 1989 

August 1990 

Number of 

Comparisons 

21 

4 

9 

11 

north/south 

8mm 

27 

20 

9 

east/west 

19 mm 

40 

25 

20 

SURVEY RESULTS 

up/down 

49 mm 

66 

60 

55 

13 

Table 6. Average root-mean-square error of each GPS survey 

(5x). 

compute baseline distances so that comparisons can be 

made between GPS and trilateration measurements made 

between several pairs of GPS benchmarks. We also examine the annual remeasurement of several stable baselines 

on the island of Hawaii so as to have yet another indication of the accuracy of our GPS surveys. A short subsection will report the geoid heights determined across 

Hawaii by the difference between geometric heights computed from the 1989 GPS survey and orthometric heights 

measured by a 1989 leveling survey. The remainder of this 

section reports the GPS results for four areas on Hawaii: 

the summit area of Kilauea, the south flank of Kilauea, the 

summit area of Mauna Loa, and the southwest coast of the 

island along the Kealakekua fault system. 

Survey north/south east/west 

April 1987 9mm 12mm 

August 1988 IS 45 

August 1989 9 21 

August 1990 9 24 

Table 7. WGS-84 Cartesian coordinates. 

Station Name 

LYMAN2 

66YY 

AINAPO TRAIL 

APUAPOINT 

BM80-t 2 

GOAT 

HALON A 

HAWAIIAN ACRES 

HAWAIIAN BEACHES 

HEIHEIAHULU 

HILINAPALI 

HP6 

HULUHULU1 

HV07 

KAENA POINT2 

KAIWIKI 

KALALUA 

KALOLI-2 

KAMA KAlA 

KAMOAMOA 

KAPAPALA1 

KAPUKAPU 

KEAAU 

KEAKAPULU FLATS 

KOAE 

KULANI 1 

MAUNA LOA STRIP1 

MILOLII 

MOANA HAUAE2 

MOUNTAIN VIEW 

NALI 

PALl 

PAPAALOA 

SANDHILL 

ULAULA 

UWEKAHUNA 

WUNGRANCH1 

Benchmark 

LYMAN N0.2 

66YYRESET 

HVO 87-107 

APUAPOINT 

80-1 

(none) 

HALON A 

HVO 87-102 

HVO 87-103 

unmarked pipe 

HILINA RESET 1975 

HP-6 EL 124.42 

HULUHULU 

HV07 

KAENAPT 

HAWAII 1210 FEET 

iron rod 

KALOLI 2 

HV0128 

HV0158 

KAPAPALA 1949 

US COAST+ GEOD 

KEAAU 1949 

HVO 146 

iron rod 

iron rod 

HVO 87-108 

NO 3 1973 

MOANAHAUAE 

HVO 87-101 

NALI 

HVOIII 

HAWAII 1912 

HV0119 

(none) 

HV0113 

HVO 87-106 

up/down 

51 mm 

55 

47 

51 

STATION COORDINATES 

For each of our four annual surveys, station positions 

are listed in table 7 in terms ofWGS-84 Cartesian coordinates 

and in table 8 in terms of latitude, longitude, and height 

X 

Aprill987 

-544597 1 .060 

-5451325.398 

-5476761.807 

-5467568.137 

-5465079.863 

-5467608.099 

-5446655.633 

-5451577.258 

-5446938.745 

-5453582.210 

-5472049.198 

-5468952.383 

-5465315.586 

-5443443.287 

-5463732.308 

-5448549.199 

-5457770.802 

-5444567.086 

-5474740.771 

-5459919.843 

-5479877.125 

-5449690.942 

-5475056.854 

-5470945.407 

-5464987.193 

-5470031.250 

-5501158.825 

-5453129.971 

-5454498.572 

-5476894.449 

-5468120.434 

-5445482.138 

-5468453.448 

-5467410.052 

-5460266.860 

y 

-2533159.910 

-2548417.316 

-2500750.780 

-2527222.758 

-2528993.779 

-2523137.994 

-2546628.191 

-2539136.530 

-2548835.776 

-2544183.916 

-2516015.185 

-2455489.152 

-2524702.702 

-2557471.217 

-2533690.143 

-2525466.395 

-2537400.189 

-2545063.058 

-2509853.291 

-2538708.025 

-2503425.017 

too many cycle slips 

-2535471.975 

-2504291.545 

-2513760.934 

-2513732.093 

-2506030.587 

-2459964.749 

-2548539.545 

-2531143.579 

-2511431.940 

-2520350.115 

-2512895.990 

-2516197.499 

too many cycle slips 

-2516254.159 

-2526844.826 

z 

2138839. 199 

2107739.303 

2102901.040 

2090533.637 

2096703.340 

2097760.414 

2121413.206 

2118338.297 

2118100.255 

2107869.200 

2094380.298 

2170430.768 

2102542.641 

2116435.666 

2092766.937 

2142425.664 

2105661.971 

2128318.679 

2095095.162 

2096614.956 

2088384.626 

2127198.360 

2102271.274 

21 00840.817 

2118309.705 

2115499.990 

2082660.333 

2102293.276 

2120875.223 

2085450.362 

2100336.740 

2164470.593 

2104808.300 

2107790.371 

2112234.315 
14 GLOBAL POSITIONING SYSTEM MEASUREMENTS ON THE ISLAND OF HAWAII FROM 1987 TO 1990 

Table 7. WGS-84 Cartesian coordinates--Continued. 

Station Name Benchmark X y z 

August 1988 

LYMAN2 LYMAN N0.2 -5445971.060 -2533159.910 2138839.199 

66YY 66YYRESET -5451325.344 -2548417.297 2107739.281 

*APUAPOINT APUAPOINT -5467567.254 -2527222.859 2090533.605 

BM80-1 80-1 -5465080.020 -2528993.892 2096703.340 

*CAPTAIN COOK HVO 88-12 -5491390.756 -2455768.505 2114392.958 

*HAWAllAN ACRES HVO 87-102 -5451577.189 -2539136.473 2118338.281 

*HAWAllAN BEACHES HVO 87-103 -5446938.744 -2548835.762 2118100.236 

*HILINA PALl lllLINA RESET 1975 -5472049.262 -2516015.193 2094380.277 

*HP6 HP-6 EL 124.42 -5468952.469 -2455489.146 2170430.817 

*HULUHULU HULUHULU -5465315.635 -2524702.846 2102542.669 

HV073 HV07 -5443443.246 -2557471.171 2116435.634 

KAENAPOINT KAENAPT -5463732.443 -2533690.202 2092766.894 

KAILUA HVO 88-11 -5489953.972 -2443731.460 2130483.489 

*KALALUA iron rod -5457770.667 -2537400.132 2105661.884 

*KALOLI-2 KALOLI2 -5444567.019 -2545063.082 2128318.688 

*KAMAKAIA HV0128 -5474740.772 -2509853.226 2095095.101 

KAMOAMOA3 HV0158 -5459919.938 -2538708.062 2096614.939 

*KAPUKAPU US COAST+ GEOD -5470259.728 -2520715.707 2092292.353 

KEAAU4 KEAAU 1949 -5449691.003 -2535472.008 2127198.369 

KEAKAPULU FLATS5 HVO 146 -5475056.872 -2504291.571 2102271.122 

KEEl KEEl NO BASE 1948 -5492297.155 -2454606.114 2112006.028 

*KOAE iron rod -5470945.298 -2513760.942 2100840.738 

*KULANI iron rod -5464987.225 -2513732.122 2118309.733 

*MAUNA LOA STRIP HVO 87-108 -5470031.158 -2506030.527 2115499.937 

*MILOLII NO 3 1973 -5501158.943 -2459964.773 2082660.384 

*ML16 ML1 -5482189.891 -2487576.651 2111928.098 

*MOANA HAUAE MOANAHAUAE -5453130.093 -2548539.625 2102293.331 

MOUNTAIN VIEW HVO 87-101 -5454498.531 -2531143.567 2120875.216 

*OUO 76-16 -5483781.073 -2476836.254 2116261.294 

*PALl HV0111 -5468120.483 -2520350.105 2100336.739 

POLIAHU HVO 88-14 -5464796.210 -2492640.467 2150664.398 

SANDHILL HV0119 -5468453.371 -2516197.525 2104808.228 

ULAULA (none) too many cycle slips 

UWEKAHUNA HV0113 -5467410.125 -2516254.206 2107790.329 

*WUNGRANCH HVO 87-106 -5460266.860 -2526844.777 2112234.281 

August 1989 

LYMAN2 LYMAN N0.2 -5445971.060 -2533159.910 2138839.199 

*1899 1899 -5473028.975 -2495131.859 2123112.472 

66YY 66YYRESET -5451325.206 -2548417.264 2107739.012 

AHUA HVO 114 -5467762.194 -2518810.862 2103350.702 

APUAPOINT APUAPOINT -5467568.214 -2527222.856 2090533.550 

BM80-1 80-1 -5465079.968 -2528993.943 2096703.241 

CAPTAIN COOK HVO 88-12 -5491390.780 -2455768.482 2114392.986 

FERN FOREST HVO 89-1 -5458401.521 -2531794.233 2111447.523 

GOAT (none) too many cycle slips 

*HALON A HALON A -5446655.682 -2546628.266 2121413.203 

HAWAIIAN ACRES HVO 87-102 -5451577.256 -2539136.571 2118338.230 

HAWAIIAN BEACHES HVO 87-103 -5446938.791 -2548835.809 2118100.191 

HEIHEIAHULU unmarked pipe -5453581.821 -2544183.836 21 07868.654 

lllLINAPALI lllLINARESET 1975 -5472049.310 -2516015.261 2094380.281 

*HP6 HP-6 EL 124.42 -5468952.458 -2455489.178 2170430.801 

HULUHULU HULUHULU -5465315.541 -2524702.753 2102542.539 

HV07 HV07 -5443443.225 -2557471.169 2116435.583 

KAENAPOINT KAENAPT -5463732.379 -2533690.308 2092766.772 

KAILUA HVO 88-11 -5489953.905 -2443731.458 2130483.521 

KALALUA iron rod -5457770.435 -2537400.232 2105661.541 

KALOLI-2 KALOLI2 -5444567.061 -2545163.049 2128318.653 

KAMAKAIA HV0128 -5474740.739 -2509853.306 2095095.133 

KAMOAMOA HV0158 -5459919.888 -2538708.170 2096614.736 

KAPUKAPU US COAST+ GEOD -5470259.819 -2520715.914 2092292.421 

KEAAU KEAAU 1949 -5449690.933 -2535471.995 2127198.346 

KEAKAPULU FLATS HVO 146 -5475056.844 -2504291.566 2102271.243 

KEEl KEEl NO BASE 1948 -5492297.052 -2454606.041 2112006.005 

*KOAE iron rod -5470945.340 -2513761.059 2100840.712 

KULANI iron rod -5464987.184 -2513732.054 2118309.681 

MAUNA KEA SUMMIT SUMMIT 1955 -5464366.269 -2493933.083 2150467.594 
SURVEY RESULTS 15 

Table 7. WGS-84 Cartesian coordinates-Continued. 

Station Name Benchmark X y z 

August 1989---Continued 

*MAUNA LOA STRIP HVO 87-108 -5470031.266 -2506030.612 2115500.00 I 

MILOLII NO 3 1973 -5501158.841 -2459964.734 2082660.358 

MLI 7 MLI -5482189.849 -2487576.633 2111928.084 

*MLO STAIR 1955 -5477995.864 -2487729.829 2120552.036 

MOANAHAUAE MOANAHAUAE -5453130.035 -2548539.796 2102293.102 

MOUNTAIN VIEW HVO 87-101 -5454498.51 0 -2531143.587 2120875.187 

*NALI NALI -5476894.565 -2511431.968 2085450.341 

ouo 76-16 -5483781.114 -2476836.302 2116261.342 

PALl HV011l -5468120.382 -2520350.139 2100336.671 

POLIAHU8 HVO 88-14 -5464796.225 -2492640.410 2150664.397 

SANDHILL HV0119 -5468453.271 -2516197.535 2104808.141 

*ULAULA (none) -5480137.507 -2505453.017 2084773.267 

UWEKAHUNA HVOI13 -5467410.090 -2516254.227 2107790.279 

WUNGRANCH HVO 87-106 -5460266.904 -2526844.876 2112234.303 

August 1990 

LYMAN2 LYMAN N0.2 -5445971.060 -2533159.910 2138839.199 

1899 CONE 1899 -5473028.901 -2495131.848 2123112.458 

66YY 66YYRESET -5451325.099 -2548417.226 2107738.975 

AHUA HVO 114 -5467762.082 -2518810.858 2103350.659 

APUAPOlNT APUAPOINT -5467568.274 -2527222.933 2090533.506 

CAPTAIN COOK HVO 88-12 -5491390.749 -2455768.481 2114392.971 

ELEELE PUU ELEELE 1976 -5478438.231 -2494590.287 2110845.607 

FERN FOREST HVO 89-1 -5458401.501 -2531794.227 2111447.505 

HAWAIIAN ACRES HVO 87-102 -5451577.159 -2539136.504 2118338.180 

HAWAIIAN BEACHES HVO 87-103 -5446938.735 -2548835.790 2118100.164 

HEIHEIAHULU unmarked pipe -5453581.870 -2544183.873 2107868.643 

HILINAPALl HILINARESET 1975 -5472049.341 -2516015.326 2094380.269 

HP6 HP-6 EL 124.42 -5468952.522 -2455489.177 2170430.841 

HULUHULU HULUHULU -5465315.402 -2524702.752 2102542.450 

HV07 HV07 -5443443.291 -2557471.211 2116435.619 

August 1990 

KAENAPOINT KAENAPT -5463732.427 -2533690.370 2092766.722 

KAILUA HVO 88-11 -5489953.952 -2443731.463 2130483.521 

KALALUA iron rod -5457770.357 -2537400.255 2105661.487 

KALOLI-2 KALOLI 2 -5444567.092 -2545063.022 2128318.663 

KAMOAMOA HV0158 -5459919.910 -2538708.316 2096614.692 

KEAAU KEAAU 1949 -5449690.867 -2535471.949 2127198.322 

KEEl KEEl NO BASE 1948 -5492297.105 -2454606.052 2112006.018 

KULANl iron rod -5464987.154 -2513732.018 2118309.662 

MAUNALOA STRIP HVO 87-108 -5470031.229 -2506030.590 2115499.970 

MILOLII NO 3 1973 -5501159.002 -2459964.743 2082660.394 

MLI 9 ML1 -5482189.851 -2487576.616 2111928.065 

MLO STAIR 1955 -5477995.802 -2487729.798 2120552.010 

MOANAHAUAE MOANAHAUAE -5453129.996 -2548539.786 2102293.050 

MOUNTAIN VIEW HVO 87-101 -5454498.581 -2531143.638 2120875.207 

ouo 76-16 -5483781.016 -2476836.353 2116261.327 

PALl HV0111 -5468120.269 -2520350.184 2100336.629 

POLIAHU HVO 88-14 -5464796.254 -2492640.440 2150664.422 

SANDHILL HVOI19 -5468453.199 -2516197.620 2104808.089 

UWEKAHUNA HV0113 -5467410.042 -2516254.240 2107790.215 

WUNGRANCH HVO 87-106 -5460266.821 -2526844.867 2112234.270 

*Loss of satellite 9, so daily observing sessions shortened to 4.2 hours. 1 Measured with respect to UWEKAHUNA coordinates in this table. 2Measured with respect to KAMOAMOA coordinates in this table. 

3Measured with respect to KAENA POINT coordinates in this table. 4Measured with respect to 66YY coordinates in this table. 

5Measured with respect to KEAAU coordinates in this table. 6Measured with respect to QUO coordinates in this table. 7Relative to the 1988 location of OUO coordinates in this table. 

8Relative to HP6 coordinates in this table. 

9Relative to the 1988 location of OUO coordinates in this table. 
16 GLOBAL POSITIONING SYSTEM MEASUREMENTS ON THE ISLAND OF HAWAII FROM 1987 TO 1990 

Table 8. Latitude, longitude, and height. 

Station Name Latitude Longitude Height, M 

April1987 

LYMAN2 19° 43' 21.90783" -155° 3' 17.26675" 26.030 

66YY 19 25 25.86693 -154 56 40.48070 254.948 

AINAPO TRAIL 19 22 24.01569 -155 27 28.90794 1570.134 

APUAPOINT 19 15 35.48955 -155 11 33.52729 24.242 

BM80-1 19 19 1.14017 -155 10 2.70305 632.265 

GOAT 19 19 35.31428 -155 13 41.10818 829.716 

HALON A 19 33 19.18200 -154 56 28.23862 114.842 

HAWAIIAN ACRES 19 31 30.89500 -155 1 32.49825 303.809 

HAWAIIAN BEACHES 19 31 24.68650 -154 55 23.76130 129.953 

HEIHEIAHULU 19 25 27.10891 -154 59 24.68727 537.243 

HILINAPALI 19 17 40.25410 -155 18 26.33012 706.368 

HP6 20 1 33.92022 -155 49 13.92297 59.044 

HULUHULU 19 22 17.38996 -155 12 19.52065 1069.214 

HV07 19 30 28.21852 -154 50 4.70910 46.267 

KAENAPOINT 19 16 52.24748 -155 7 17.34985 40.369 

KAIWIKI 19 45 21.58620 -155 7 54.20832 388.607 

KALALUA 19 24 9.32973 -155 3 56.05541 683.630 

KALOLI-2 19 37 18.60751 -154 56 46.53846 23.016 

KAMA KAlA 19 18 3.53623 -155 22 16.57665 824.707 

KAMOAMOA 19 19 4.80949 -155 3 46.46580 43.199 

KAPAPALA 19 14 16.13163 -155 26 49.92369 493.848 

KEAAU 19 36 37.84746 -155 2 59.16437 202.708 

KEAKAPULU FLATS 19 22 5.55002 -155 25 14.29943 1286.773 

KOAE 19 21 19.41793 -155 19 20.69906 1009.501 

KULANI 19 31 13.73647 -155 17 56.29830 1706.544 

MAUNA LOA STRIP 19 29 32.74787 -155 23 8.42127 2060.734 

MILOLII 19 11 4.37055 -155 54 25.69945 19.580 

MOANAHAUAE 19 22 20.59660 -154 57 2.87443 36.977 

MOUNTAIN VIEW 19 32 59.47906 -155 6 23.34643 473.112 

NALI 19 12 39.38878 -155 21 58.17556 113.283 

PALl 19 21 1.92384 -155 15 15.18000 1020.165 

PAPAALOA 19 58 4.84899 -155 13 42.09289 297.567 

SANDHILL 19 23 34.56079 -155 17 29.18271 1150.027 

UWEKAHUNA 19 25 15.99833 -155 17 12.47169 1269.244 

WUNGRANCH 19 27 54.42314 -155 10 0.26728 817.255 

August 1988 

LYMAN2 19° 43' 21.90783" -155° 3' 17.26675" 26.030 

66YY 19 25 25.86689 -154 56 40.48052 254.887 

*APUAPOINT 19 15 35.48697 -155 11 33.52584 24.372 

BM80-1 19 19 1.13815 -155 10 2.70181 632.444 

*CAPTAIN COOK 19 29 12.57364 -155 54 20.32293 495.816 

*HAWAIIAN ACRES 19 31 30.89547 -155 I 32.49904 303.722 

*HAWAIIAN BEACHES 19 31 24.68600 -154 55 23.76171 129.939 

*HILINA PALl 19 17 40.25281 -155 18 26.33075 706.419 

*HP6 20 1 33.92088 -155 49 13.92436 59.133 

*HULUHULU 19 22 17.38969 -155 12 19.51686 1069.323 

HV07 19 30 28.21816 -154 50 4.70995 46.203 

KAENAPOINT 19 16 52.24456 -155 7 17.34995 40.494 

KAILUA 19 38 33.31370 -156 0 17.35709 26.383 

*KALALUA 19 24 9.32864 -155 3 56.05523 683.464 

*KALOLI-2 19 37 18.60833 -154 56 46.53672 22.971 

*KAMAKAIA 19 18 3.53465 -155 22 16.57870 824.662 

KAMOAMOA 19 19 4.80787 -155 3 46.46602 43.290 

*KAPUKAPU 19 16 32.51575 -155 15 34.47644 337.607 

KEAAU 19 36 37.84701 -155 2 59.16423 202.776 

KEAKAPULU FLATS 19 22 5.54907 -155 25 14.29885 1286.750 

KEEl 19 27 55.56504 -155 55 9.39249 32.842 

*KOAE 19 21 19.41653 -155 19 20.69725 1009.384 

*KULANI 19 31 13.73690 -155 17 56.29784 1706.592 

*MAUNA LOA STRIP 19 29 32.74741 -155 23 8.42185 2060.614 

*MILOLII 19 11 4.37086 -155 54 25.70035 19.708 

*ML1 19 27 6.36432 -155 35 36.75375 4082.388 

*MOANAHAUAE 19 22 20.59685 -154 57 2.87359 37.123 

MOUNTAIN VIEW 19 32 56.47930 -155 6 23.34622 473.069 

*OUO t9 29 51.44276 -155 41 34.56397 2717.557 

*PALl 19 21 1.92337 -155 15 15.18101 1020.203 

POLIAHU 19 49 22.06399 -155 28 51.58572 4163.806 

SANDHILL 19 23 34.55921 -155 17 29.18083 1149.948 

UWEKAHUNA 19 25 15.99605 -155 17 12.47124 1269.314 

*WUNGRANCH 19 27 54.42234 -155 10 0.26878 817.224 
SURVEY RESULTS 17 

Table 8. Latitude. longitude, and height-Continued. 

Station Name Latitude Longitude Height, M 

August 1989 

LYMAN2 19° 43' 21.90783" -155° 3' 17.26675" 26.030 

*1899 CONE 19 33 45.58037 -155 29 31.01566 2905.298 

66YY 19 25 25.86013 -154 56 40.47954 254.666 

AHUA 19 22 44.83449 -155 15 57.93868 1104.856 

APUAPOINT 19 15 35.48568 -155 11 33.52536 24.3I7 

BM80-1 I9 19 1.I3539 -I 55 10 2.69946 632.387 

CAPTAIN COOK I9 29 I2.57439 -155 54 20.32370 495.838 

FERN FOREST 19 27 29.0I491 -155 6 55.14843 667.009 

*HALON A 19 33 I9.18108 -154 56 28.2370I 114.913 

HAWAIIAN ACRES I9 31 30.89280 -I 55 I 32.49694 303.801 

HAWAIIAN BEACHES I9 3I 24.68393 -154 55 23.76096 129.984 

HEIHEIAHULU I9 25 27.09634 -I 54 59 24.68409 536.697 

HILINAPALI I9 I7 40.25215 -155 18 26.32933 706.488 

*HP6 20 1 33.92032 -155 49 13.92322 59.130 

HULUHULU 19 22 17.38703 -155 12 19.51841 1069.162 

HV07 19 30 28.21680 -154 50 4.70968 46.167 

KAENAPOINT 19 16 52.24098 -155 7 17.34576 40.441 

KAILUA 19 38 33.31535 -156 0 17.35622 26.336 

KALALUA 19 24 9.31995 -155 3 56.04878 683.191 

KALOLI-2 I9 37 18.60701 -154 56 46.53835 22.982 

KAMA KAlA I9 I8 3.53560 -155 22 I6.57571 824.676 

KAMOAMOA I9 I9 4.80I63 -155 3 46.46197 43.222 

KAPUKAPU I9 I6 32.5I604 -155 I5 34.47I31 337.789 

KEAAU I9 36 37.84703 -155 2 59.16361 202.704 

KEAKAPULU FLATS I9 22 5.54907 -155 25 I4.29865 I286.763 

KEEl 19 27 55.56566 -155 55 9.39334 32.7I6 

*KOAE 19 21 19.41479 -155 I9 20.69422 I009.457 

KULANI I9 3I 13.73601 -155 I7 56.29937 1706.5I3 

MAUNA KEA SUMMIT 19 49 14.44472 -155 28 5.07329 4233.867 

*MAUNA LOA STRIP 19 29 32.74793 -155 23 8.42073 2060.76I 

MILOLII 19 11 4.37I24 -155 54 25.700I5 19.596 

ML1 I9 27 6.36441 -155 35 36.7537I 4082.34I 

*MLO 19 32 1I.32361 -155 34 32.55787 34I9.922 

MOANAHAUAE 19 22 20.58948 -154 57 2.86756 37.074 

MOUNTAIN VIEW 19 32 56.4785~1 -155 6 23.34528 473.049 

*NALI I9 12 39.38688 -155 2I 58.I7634 I13.386 

ouo 19 29 51.44362: -155 4I 34.56306 27I7.627 

PALl I9 2I 1.922I~1 -155 15 15.I785I I020.I08 

POLIAHU I9 49 22.0640CI -155 28 51.58774 4I63.796 

SANDHILL I9 23 34.55749 -155 17 29.I7907 II49.837 

*ULAULA I9 12 13.67753, -155 25 50.48436 324.550 

UWEKAHUNA I9 25 I5.99483, -155 17 I2.47012 1269.273 

WUNGRANCH I9 27 54.422I2 -155 10 0.26635 8I7.308 

August 1990 

LYMAN2 I9° 43' 21.90783" -155° 3' I7.26675" 26.030 

1899CONE I9 33 45.58072 -155 29 31.0I500 2905.228 

66YY I9 25 25.860I5 -154 56 40.479I4 254.550 

AHUA 19 22 44.83425 -155 I5 57.93720 II04.746 

APUAPOINT 19 I5 35.48332 -155 II 33.5238I 24.386 

CAPTAIN COOK 19 29 12.57422 -155 54 20.32358 495.807 

ELEELE I9 26 38.74070 -155 3I 4.78759 3238.I65 

FERN FOREST 19 27 29.0I455 -155 6 55.I4833 666.986 

HAWAIIAN ACRES 19 3I 30.89248 -155 I 32.49760 303.676 

HAWAIIAN BEACHES I9 3I 24.68369' -154 55 23.76070 129.92I 

HEIHEIAHULU I9 25 27.09528 -154 59 24.68368 536.752 

HILINAPALI 19 17 40.25111 -155 18 26.32776 706.538 

HP6 20 I 33.92097 -155 49 13.92411 59.201 

HULUHULU 19 22 17.38562 -155 12 19.51643 1069.015 

HV07 19 30 28.2I704 -'154 50 4.70936 46.254 

KAENAPOINT I9 16 52.23860 -155 7 17.34453 40.492 

KAILUA 19 38 33.31487 -156 0 17.35674 26.380 

KALALUA 19 24 9.31890 -155 3 56.04694 683.116 

KALOLI-2 19 37 18.60710 -154 56 46.53964 23.003 

KAMOAMOA 19 19 4.79935 -R55 3 46.45774 43.287 

KEAAU I9 36 37.847I7 -1155 2 59.I6408 202.623 

KEEl 19 27 55.56544 -155 55 9.39374 32.772 

KULANI 19 31 13.73584 -1155 17 56.30004 1706.468 

MAUNA LOA STRIP 19 29 32.74742 -1155 23 8.42089 2060.713 

MILOLII I9 II 4.37063 -1155 54 25.70209 I9.752 

MLI 19 27 6.36386 -1155 35 36.75424 4082.331 

MLO 19 32 11.32353 -1155 34 32.55794 3419.850 
18 GLOBAL POSITIONING SYSTEM MEASUREMENTS ON THE ISLAND OF HAWAII FROM 1987 TO 1990 

Table 8. Latitude, longitude, and height-Continued. 

Station Name Latitude Longitude Height, M 

Augustl~ontinued 

MOANAHAUAE 19° 22' 20.58828 -154° 57' 2.86731 37.022 

MOUNTAIN VIEW 19 32 56.47818 -155 6 23.34470 473.139 

ouo 19 29 51.44385 -155 41 34.56007 2717.559 

PALl 19 21 1.92166 -155 15 15.17548 1020.016 

POLIAHU 19 49 22.06443 -155 28 51.58721 4163.844 

SANDHILL 19 23 34.55619 -155 17 29.17539 1149.793 

UWEKAHUNA 19 25 15.99323 -155 17 12.46904 1269.218 

WUNGRANCH 19 27 54.42194 -155 10 0.26545 817.224 

*Loss of satellite 9, so daily observing sessions shortened to 4.4 hours. 

above the reference ellipsoid defined in table 2. (At the 

latitude of Hawaii, 0.01" of latitude or longitude is about 0.3 

m.) Also given in table 7 is the name stamped on the benchmark or the type of mark used, such as an iron rod at 

KALALUA. All station coordinates in tables 7 and 8 are 

relative to the position of LYMAN2 computed for the April 

1987 survey using NSWC orbits and listed in the bottom 

half of table 4. 

Most station positions were computed from baselines that 

included LYMAN2 as one endpoint. The exceptions are 

given in a footnote. For example, for the 1987 survey, the 

position of HULUHULU was computed from a baseline 

that had HULUHULU and UWEKAHUNA as endpoints. If 

in some future re-analysis of these surveys the position of 

UWEKAHUNA is adjusted, then the position of HULUHULU must be adjusted by the same amount. During the 1989 

and 1990 surveys, LYMAN2 was occupied every day. 

The loss of satellite 9 during a major portion of the 

1988 and 1989 surveys reduced the duration of our daily 

observing sessions, which resulted in less accurate measurements. Asterisks in tables 7 and 8 identify the stations 

surveyed when satellite 9 was unavailable. 

The position of a few stations, such as KAPUKAPU in 

1987, could not be determined because of a large number 

of cycle slips, mostly in L2-carrier phase measurements. 

As a result, no coordinates are given for a few stations. 

Differences in measured station positions of four 

pairs of surveys are listed in table 9. The first three survey 

pairs are for successive annual surveys between 1987 and 

1990. The last pair is for the full four years from 1987 to 

1990. A positive difference means a measured change to 

the north, east, or up. At the bottom of table 9, an uncertainty for each component for each survey pair was computed as the square root of the sum of the squares of the 

uncertainties given in table 5 for the appropriate component and survey. For example, the daily variation in measuring the north/south component was 8 mm in 1987 

and 27 mm in 1988. (As mentioned in an earlier section, 

we assume these daily variations are the accuracy of each 

survey.) The uncertainty in computing the difference 

in north/south positions between 1987 and 1988 was 

~272 + 82 = 28mm. 

COMPARISON OF GPS AND 

TRILATERATION MEASUREMENTS 

Trilateration measurements were made in the summit 

area of Kilauea at about the same time as the GPS surveys. The station-to-station distances measured using a 

laser instrument and GPS are listed in table 10 and plotted 

in figure 10. (The 1990 trilateration measurements of MLStrip were not to the GPS benchmark (MAUNA LOA 

STRIP), but to another benchmark (stamped ML STRIP) 

located about 200 m east. Trilateration measurements were 

also made to ML STRIP in August 1989, and so a change 

in line length measured to ML STRIP between August 

1989 and October 1990 was assumed to be the same as a 

change in line length to the GPS benchmark.) 

Distances computed from our laser measurements are almost always longer than those computed from GPS (figs. 10 

and 11 and last column in table 1 0) because an inadequate 

refraction correction has been made to the laser measurements. Air temperatures that were measured only at the 

endpoints, used to compute a refraction correction, are higher 

than the air temperature averaged along the line-of-sight, and 

so computed distances are slightly too long. To illustrate this 

bias, we have plotted in figure 11 the differences between 

laser and GPS measurements as a function of baseline distance. The dashed line indicates a bias of 5 ppm, which 

means, on average, endpoint temperatures overestimate average line-of-sight temperatures by about 5°C. (When air 

temperatures are measured along the entire line between two 

stations, distances determined by laser and GPS measurements agree to within 0.2 ppm (Prescott and others, 1989).) 

In studying active volcanoes, we are concerned with 

changes in station positions, not absolute positions, and so for 

our purposes, the bias between laser and GPS measurements 

is not as great as indicated by figure 11. Furthermore, on 

active volcanoes we are more apt to measure changes of ten 
SURVEY RESULTS 19 

Table 9. Coordinate differences between GPS surveys. 

[Values expressed in millimeters] 

1988-1987 1989-1988 1990-1989 1990-1987 

Station name N/S EIW U/D N/S EIW U/D N/S EIW U/D N/S EIW U/D 

1899 CONE 11 19 -70 

66YY -1 6 -61 -208 28 -221 2 12 -116 -207 46 -398 

AHUA -6 44 -20 

APUAPOINT -79 42 130 -40 14 55 -70 45 69 -189 101 144 

BM80-1 -62 36 179 -85 69 -57 

CAPTAIN COOK 22 -31 22 -4 11 -9 

FERN FOREST -9 3 -23 

HAWAIIAN ACRES 14 -23 -87 -82 61 79 -9 -20 -125 -77 18 -133 

HAWAIIAN BEACHES -15 -12 -13 -64 22 45 -6 7 -63 -85 17 -31 

HEIHEIAHULU -31 12 55 -418 104 -491 

HILINAPALI -40 -22 51 -20 41 69 -30 46 50 -90 69 170 

HP6 20 -40 89 -17 32 -37 18 -25 72 21 -33 157 

HULUHULU -8 111 109 -82 -45 -161 -41 57 -147 -131 123 -199 

HV07 -11 -24 -64 -42 7 -36 -9 10 87 -44 -7 -13 

KAENAPOINT -89 -3 125 -110 122 -53 -71 35 51 -270 154 129 

KAILUA 51 25 -47 -15 -15 44 

KALALUA -33 5 -166 -268 188 -273 -30 53 -75 -331 246 -514 

KALOLI-2 25 50 -45 -41 -47 11 4 -37 21 -12 -34 -13 

KAMA KAlA -49 -60 -45 28 87 14 

KAMOAMOA -51 -6 91 -191 118 -68 -69 123 65 -311 235 88 

KAPUKAPU 9 150 182 

KEAAU -13 4 68 0 18 -72 5 -14 -81 -8 8 -85 

KEAKAPULU FLATS -29 17 -23 0 5 13 

KEEl 24 -13 -37 -6 -11 56 

KOAE -43 53 -117 -53 88 73 

KULANI 14 13 48 -28 -44 -79 -4 -20 -45 -18 -51 -76 

MAUNALOA STRIP 14 -17 -120 -16 32 147 15 -4 -48 13 11 -21 

MILOLII 9 -26 128 12 6 -112 -17 -57 196 4 -77 172 

MLJ 3 1 -46 -17 -15 -9 

MLO -1 -2 -72 

MOANAHAUAE 8 24 145 -227 176 -49 -35 7 -52 -254 207 44 

MOUNTAIN VIEW 8 5 -43 -24 28 -20 -10 16 90 -26 49 27 

ouo 26 27 70 9 87 -68 

PALl -15 -30 38 -38 73 -95 -12 88 -92 -65 131 -149 

POLIAHU 1 -58 -11 11 15 49 

SANDHILL -48 55 -79 -53 51 -111 -39 107 -44 -140 213 -234 

UWEKAHUNA -70 14 69 -38 32 -40 -47 32 -56 -155 78 -27 

WUNGRANCH -24 -44 -31 -7 71 84 -5 26 -84 -36 53 -31 

1 Uncertainties (28) (44) (82) (34) (47) (96) (22) (32) (89) (12) (28) (74) 

1

Uncertainties are the square root of the sum of the squares of the uncertainties given for the appropriate component for 

each survey in table 5. For example, for the 1988 and 1987 surveys, the uncertainty of the difference of the N/S component was 

Jd:;; [ 27 + 8 = 28]. 

parts per million or more, in which case laser and GPS 70 nun or more. There appears to be a trend of increasing 

measurements record similar changes in line lengths (fig. 12). elevation difference between LYMAN2 and HP6, which 

may represent a mistake in measuring antenna height in 

1987 or 1990 or illustrate the limitation of the single-paramSTABLE BASELINES eter tropospheric model and the lack of water vapor measurements. (LYMAN2 is on the windward side of the island 

Annual measurements across three baselines, which did where annual rainfall is 180 inches (5 m); HP6 is on the arid 

not span areas of seismic or volcanic activity, are shown in leeward side where annual rainfall is less than 0.1 m.) AIfigure 13A. The range of north/south or east/west positions though there is a 4,000-m-elevation difference between 

is usually within 30 mm, with the 1988 measurement show- LYMAN2 and POLIAHU, this baseline has the same reing the largest variation. The range of vertical positions is peatability as the other two stable baselines. 
20 GLOBAL POSITIONING SYSTEM MEASUREMENTS ON THE ISLAND OF HAWAII FROM 1987 TO 1990 

Table 10. Comparison of trilateration and GPS measurements. 

Stations Trilateration GPS Survey Difference 

Date Length, m Date Length, m m 

Uwekahuna- Sandhill Nov. 5, 1986 3159.911 Apr 1987 3159.847 0.064 

Aug. 4, 1988 3159.883 Aug 1988 3159.826 0.057 

Aug. 18, 1989 3159.850 Aug 1989 3159.840 0.010 

Oct. 2, 1990 3159.856 Aug 1990 3159.845 0.011 

U wekahuna - Pa1i Nov. 5, 1986 8534.568 Apr 1987 8534.525 0.043 

Aug.4, 1988 8534.524 Aug 1988 8534.460 0.064 

Aug. 18, 1989 8534.491 Aug 1989 8534.476 0.015 

Oct. 2, 1990 8534.489 Aug 1990 8534.467 0.022 

Uwekahuna - Kulani Nov. 4, 1986 11085.428 Apr 1987 11085.461 -0.033 

Aug.4, 1988 11085.582 Aug 1988 11085.541 0.041 

Aug. 18, 1989 11085.601 Aug 1989 11085.560 0.041 \ 

Oct. 2, 1990 11085.645 Aug 1990 11085.610 0.035 

Uwekahuna - MLStrip Jul. 2, 1987 13070.316 Apr 1987 13070.208 0.108 

Aug. 4, 1988 13070.380 Aug 1988 13070.252 0.128 

Aug. 18, 1989 13070.378 Aug 1989 13070.298 0.080 

Oct. 18, 1990 13070.430* Aug 1990 13070.347 0.083 

Sandhill - Pali Nov. 5, 1986 6111.516 Apr 1987 6111.462 0.054 

Aug. 4, 1988 6111.460 Aug 1988 6111.378 0.082 

Aug. 18, 1989 6111.370 Aug 1989 6111.381 -0.011 

Oct. 19, 1990 6111.335 Aug 1990 6111.349 -0.014 

Sandhill- Kulani Nov. 4,1986 14155.598 Apr 1987 14155.603 -0.005 

Aug. 4, 1988 14155.735 Aug 1988 14155.671 0.064 

Aug. 18, 1989 14155.743 Aug 1989 14155.703 0.040 

Oct. 2, 1990 14155.744 Aug 1990 14155.746 -0.002 

Sandhill - MLStrip Jul. 2, 1987 14838.157 Apr 1987 14838.052 0.105 

Aug. 4, 1988 14838.238 Aug 1988 14838.123 0.115 

Aug. 18, 1989 14838.284 Aug 1989 14838.203 0.081 

Oct. 18, 1990 14838.338* Aug 1990 14838.295 0.043 

Pali - MLStrip Jul. 2, 1987 20943.477 Apr 1987 20943.358 0.119 

Aug. 4, 1988 20943.527 Aug 1988 20943.342 0.185 

Aug. 18, 1989 20943.511 Aug 1989 20943.422 0.089 

Oct. 18, 1990 20943.546* Aug 1990 20943.482 0.064 

*Change relative to trilateration benchmark. 

Annual measurements of three shorter baselines are shown 

in figure 13B. MAUNA LOA STRIP and KEAKAPULU 

FLATS both lie in the Hilea-Kaoiki seismic area, where 

several earthquakes greater than 5.0 magnitude occurred between 1981 and 1983. During the four years spanned by our 

surveys, however, earthquake activity was low, and so for that 

time period we consider these baselines stable. The range of 

north/south or east/west positions was within 30 mrn; however, the range of vertical positions was more than 100 mrn 

for the baselines that included KULANI and MAUNA LOA 

STRIP. (If the 1988 survey is excluded, the range of vertical 

positions for these two baselines was less than 60 mrn. Both 

baselines were measured during the shortened observing sessions in 1988; a six-hour observing session was used to 

measure the baseline to KEAKAPULU FLATS.) In view of 

these measurements, as well as the earlier discussion about 

daily variations in repeating baseline measurements, on average, single-day measurements yield north/south and east/west 

positions to within 30 mrn and vertical positions to 60 mm. 

Those baselines measured during shortened observing sessions in 1988 are less accurate by as much as a factor of two. 

HEIGHT OF THE GEOID 

Though vertical positions are the most difficult to 

measure with GPS, an accuracy of 100 mm or better is 

adequate to determine height of the geoid if elevations 

from leveling surveys are also available. GPS measures 

geometric heights, the height that would be measured if a 

long graduated bar extended from Earth's center of mass 

to the surface. Elevations determined from leveling surveys are orthometric heights, which are influenced by the 

gravity field. Height of the geoid is the difference between 

these two elevations, here defined as geometric minus 

orthometric elevation. 
SURVEY RESULTS 

o laser measurements 

• GPS measurements 

14838.4-,----------------., 

Sandhill - Mauna Loa Strip 

~ 14838.3 

~ 

cU 14838.2 

~ 0 14838.1 

14155.8...,-----------------, 

tl.l Sandhill - Kulani 

~ 

~ 14155.7 

i 14155.6 tl.l 

0 

3160.0~---------------, 

tl.l Uwekahuna- Sandhill 

~ 8 3159.9 

i 3159.8 tl.l 

0 

8534.7-.------------------, 

i 8534.6 

i 8534.5 

0 

U wekahuna - Pali 

11085.7-.------------------, 

~ Uwekahuna- Kulani 

8 11085.6 

i 11085.5 tl.l 

0 

1986 

13070.5-,-----------------, 

tl.l 

~ 

Uwekahuna -Mauna Loa Strip 

~ 13070.4 

cU 

~ 13070.3 tl.l 

0 

1986 

6111.6-.------------------, 

tl.l Sandhill - Pali 

~ 

~ 6111.5 

i 6111.4 tl.l 

a 

1986 

20943.6~----------------, 

~ Pali - Mauna Loa Strip 

8 20943.5 

i 20943.4 tl.l 

0 

1986 1990 

Figure 10. Comparison of baseline distances determined by laser and GPS measurements. Location of each baseline is shown 

in the upper lefthand corner. 

21 
22 GLOBAL POSITIONING SYSTEM MEASUREMENTS ON THE ISLAND OF HAWAII FROM 1987 TO 1990 

e 

e 200 

Cl) 

~ 

C) 100. 

~ 

= 

•1"'"1 = 0 e 

= 0 -100. •J:1 

C'd 

~ 

B 

~ 

C'd -200 

·c 

~ 0 

• 

: I 5 yytn __ ._ ____ _ [] • ,.a..----- • 

8 [] [] -----"tl • ---a-- B c• ---rr---- B .., 

I 

5 

l:i u [] 

c All lines, except to MLStrip 

• Lines to MLStrip I I I 

10 15 20 

Baseline length, km 

25 

Figure 11. Difference between laser and GPS measurements, plotted 

as a function of baseline length. A difference of 5 parts per million is 

shown as a dashed line. 

e 300 

e 

~ ~ 9t .s 200-

OJ) 100- = ~ 

0 + ~ G) 0 .... 

.5 - ~ -100- •1"'"1 = + 

0 -200- 0 

OJ) c Trilateration [+/- 5 ppm] 

a -300 

• GPS [+/- 30 nun] 

..d I I I I 

u 0 5 10 15 20 25 

Baseline length, km 

Figure 12. Measured changes in line lengths, determined from laser 

and GPS measurements, between April 1987 and August 1990. 

We illustrate geoid height by considering different 

determinations of the elevation of the summit of Mauna 

Kea, the highest peak in the Pacific basin. Leveling and 

triangulation surveys were used to determine the summit 

of Mauna Kea to be 4,205 meters above sea level (Mauna 

Kea quadrangle 7.5-minute topographic series, U.S. Geological Survey, 1982). A GPS measurement made on August 25, 1989 was used to compute an elevation difference 

of 4,207.8 m between LYMAN2 and the benchmark at the 

true summit of Mauna Kea (stamped SUMMIT 1955). 

From a 1957 survey, LYMAN2 was 8.2 m above mean 

high sea level, established at a nearby tide gage in Hilo 

Bay. If we include a 0.2 m rise of sea level in Hilo Bay 

since 1957 (Moore, 1987), the present geometric height of 

the summit of Mauna Kea is 4,215.8 m above mean sea 

level in Hilo Bay. The difference between geometric and 

orthometric elevations means the geoid at the summit of 

Mauna Kea is raised 11 m, which corresponds to a horizontal gradient between Hilo and Mauna Kea of 0.24 ml 

km. This is similar to the maximum geoid heights determined elsewhere along the Hawaiian island chain, for example across Molokai where the geoid height rises 12 m 

over a distance of about 100 km (Watts, 1979). 

We have determined geoid heights elsewhere on the island of Hawaii using geometric elevations from GPS 

measurements and orthometric elevations determined either 

from an extensive leveling survey conducted across Kilauea 

in February 1989 or orthometric elevations of several GPS 

benchmarks taken from USGS topographic maps. Relative 

to LYMAN2, geoid heights are about 11 m in the summit 

areas of Mauna Kea and Mauna Loa and 5 m in the summit area of Kilauea (fig. 14). LYMAN2, KAPUKAPU, and 

MILOLII are at nearly the same geoid height. 

As suggested by Watts (1979), our map of geoid heights 

across Hawaii probably reflects two major components: (1) 

the broad high shape of the island above the sea floor and 

(2) subsidence of the rigid lithosphere into a viscous asthenosphere caused by the weight of the volcanoes. 

SLOW SUBSIDENCE OF THE 

SUMMIT AREA OF KILAUEA VOLCANO 

Leveling surveys have shown a slow subsidence of 

the summit area of Kilauea since the beginning of an 

eruption along the east rift zone in January 1983. HV027, 

a leveling benchmark located near the UWEKHUNA GPS 

benchmark, 3 km north of the center of subsidence, has 

subsided at an annual rate of 20 mrnlyr since February 

1983 (fig. 15). HV032, located within 2 km of the center 

of subsidence, has subsided four times faster. Our GPS 

measurements also recorded the subsidence, as well as contraction of the summit area. 

The three-dimensional displacement of UWEKAHUNA and SANDHILL, relative to LYMAN2, are shown in 

figure 16. Between April 1987 and August 1990, UWEKAHUNA moved south-southeast at a rate of 50 mm/yr, 

and SANDHILL moved southeast at a faster rate of 80 

mm/yr (fig. 16). The subsidence rate of 20 mm/yr near 

..... Figure 13. Measurements of six stable baselines on the 

island of Hawaii. We suspect these were stable baselines during 

the period of our surveys because no significant seismic or volcanic activity occurred beneath these lines between 1987 and 

1990. A, Baselines between LYMAN2 and HP6, POLIAHU, and 

KAILUA. B, Baselines between LYMAN2 and KULANI, MAUNA LOA STRIP, and KEAKAPULU FLATS. An error bar is five 

times the standard error computed using the Bemese software 

package. Error bars are only shown when they are larger than the 

symbol. Within the error bars, a horizontal trend, indicated as a 

dashed line segment, can account for the measured variation of 

each component, which supports the claim that, within the uncertainty of our measurements, these were stable baselines. 
SURVEY RESULTS 23 

33396.7 A tl.l HP6 north/south 

~ 

8 33396.6 

of 

s 33396.5 

i5 

33396.4 

-80269.4 

~ HP6 east/west 

a) -80269.5 E3 

of 

~ -80269.6 tl.l 

i5 

-80269.7 

1987 1990 

59.0 

tl.l HP6 vertical 

~ 

~ 58.9 E3 

of 

~ 58.8 tl.l 

i5 

58.7 

1987 1990 

11018.8 -9151.7 

tl.l POUAHU north/south tl.l ~UA north/south 

I ~ 

11018.7 ~ -9151.8- E3 - -~- i --o -o- :-::{]_ of 

u 

11018.6 § -9151.9- tl.l tl.l 

i5 i5 

11018.5 -9152.0 

1987 1990 1987 

1

1988 11989 11990 

-44617.8 -99585.9 

tl.l POUAHU east/west tl.l ~UA east/west 

b ~ ~ -44617.9-

--~- ~ -99586.0 E3 E3 

i - of 

-44678.0-: ~ -99586.1 tl.l tl.l 

~ - tS 

-44678.1 - -99586.2 

1987 1

1988 11989 1

1990 

4163.8 26.3 

tl.l POUAHU vertical tl.l ~UA vertical 

~ ~ 

8 4163.7 E 26.2 

~ of 

4163.6 ~ 26.1 .... 

tl.l tl.l 

~ i5 

4163.5 26.0 

1987 1987 1990 
24 GLOBAL POSITIONING SYSTEM MEASUREMENTS ON THE ISLAND OF HAWAII FROM 1987 TO 1990 

B 

MAUNALOA 

\ STRIP 

KEAKAPULU 

FLATS 

-39287.9-r-----------------, 

til _ KEAKAPULU FLATS north/south 

g 

8 -39288.0-

i -39288.1~ -~--

0 

-39288.2...,·t-----r-----.----...------l 

1987 11988 11989 11990 

-38350.6 

til 

B 

KEAKAPULU FLATS east/west 

e -38350.7 

~ 

~ -38350.8 til 

0 

-38350.9 

1987 1990 

1286.7-r------------------, 

K.EAKAPULU FLATS vertical 

1286.6..: . 

1286.5~ -t=-----=-=?·---~~-- 1286.4~---~---,.-----r------1 1

1988 11989 1 1987 1990 

Figure 13.-Continued. 

-22409.3 

~ KULANI north/south 

~ -22409.4 8 

~ 

! -22409.5 

0 

-22409.6 

-25596.6 

til 

~ 

e -25596.7 

~ 

5 -25596.8 

0 

-25596.9 

1706.5 

til 

~ a> 1706.4 8 

~ 

~ til 

0 

1706.2 

-25530.2-r-----------------, 

til MAUNA LOA STRIP north/south 

~ 

6 -25530.1 

i -25530.0 - r-=.:=---......-:~=--o::..::r--,e:.---~...1. 0 

-34685.2-r-----------------, 

til 

u 

~ -34685.3 

MAUNA LOA S1RIP east/west 

8 E -34685.4 - til 

a 

til 

u 

t) 2060.5 8 

~ 

~ 2060.4 til 

a 

2060.3 
SURVEY RESULTS 25 

r 110m i 

Norrh level 

surveys 

other 

techniques 

Figure 14. Geoid heights relative to Hilo: difference between geometric and 

orthometric heights. Geometric heights determined by GPS measurements. 

Orthometric heights determined either by leveling surveys or elevations of 

topographic control points on USGS topographic maps. 

UWEKAHUN A, indicated by the leveling benchmark 

HV027, was not resolved by our GPS; however, our GPS 

measurements easily resolved the 80 mm/yr subsidence of 

SANDHILL (fig. 15). 

Assuming the subsidence pattern can be modeled as 

the contraction of a pressure source located 4 km beneath 

the subsidence center shown in figure 16, which represents 

a shallow magma reservoir, the subsidence rate at Sandhill 

corresponds to the removal of 0.01 km3/yr of magma. 

This rate is 10 percent of the average eruptive rate of 0.1 

km3/yr from 1983 to 1986, which is corrected for 20 percent vesiculation of the erupted lava (Heliker and Wright, 

1991). If the eruptive rate has continued unchanged 

through 1990, then only 10 percent of the erupted lava can 

be accounted for by net removal of magma from the summit reservoir. The other 90 percent must correspond to the 

rate magma is being supplied to Kilauea from a source 

deeper than the summit reservoir. 

SEAWARD MOVEMENT OF THE 

SOUTH FLANK OF KILAUEA VOLCANO 

Seaward displacement occurs along the most seismically active portion of the south flank, from APUA 

POINT to KAMOAMOA (fig. 17). Between the 1987 and 

1988 surveys and again between the 1989 and 1990 surveys, the coastline from APUA POINT to KAMOAMOA 

moved seaward at annual rates of 50 to 100 mm/yr. During the same time periods, no significant ground displacement was measured east of KAMOAMOA or along the 

north flank of Kilauea. 

Movement along the south flank was first revealed 

by triangulation and trilateration surveys conducted since 

1914 (Swanson and others, 1976). Seaward displacement 

is driven by intrusion of pressurized magma into a rift 

zone, which causes immediate compression of the adjacent 

section of the south flank. Persistent earthquake zones beneath the south flank reveal the most mobile sections of 

the south flank, though seaward displacement may also 

occur, at times, elsewhere on Kilauea, for example southwest of the summit area as indicated by persistent southward displacement at KOAE, KAMAKAIA, and HILINA 

PALl (fig. 17). 

During the four years of GPS measurements, the 

largest ground displacement were associated with a magnitude 6.1 earthquake on June 26, 1989, beneath the south 

flank. The epicenter was located a few kilometers north of 

the KAMOAMOA GPS station, between the axis of the 

east rift zone and the coastline (fig. 18). The focal mechanism is consistent with seaward displacement of the south 

flank over older ocean crust (Koyanagi and others, 1989). 

The pattern of horizontal displacement determined using 

GPS also indicates seaward displacement of as much as 

0.3 m (fig. 18). 

The pattern of horizontal displacement can be reproduced by a rectangular fault embedded in a homogeneous, 

isotropic, elastic half-space with displacement constant 

across the fault. Analytic expressions for surface displacement were given by Okada (1985). Eight parameters are 

determined from this model: latitude, longitude, and depth 

of one corner of the fault; length and width of the fault; 

dip and strike angle of the fault; and the amount of dipslip displacement across the fault. The values of these 
26 GLOBAL POSITIONING SYSTEM MEASUREMENTS ON THE ISLAND OF HAWAII FROM 1987 TO 1990 

0 HV023 

reference benchmark 

i 200--------------------------------- .... 0 Leveling survey: HV027 - HV023 

] 100 • GPS survey: UWEKAHUNA- L YMAN2 

] 

1990 

200 

0 Leveling survey: HV032 - HV023 

100 • GPS survey: SANDlllLL- L YMAN2 

fi 0 C) 

.§ 

] -100 

oJ 

i -200 

-5 

.g -300 

«< 

~ -400 ~ 

-500 

-600 

Figure 15. Slow subsidence of summit area of Kilauea, indicated by results of leveling surveys. Locations of leveling 

benchmarks (circles) and GPS benchmarks (triangles) shown 

at the top. Upper plot indicates slow subsidence at an average 

rate of 20 rnrnlyr of the leveling benchmark HV027, located 

near the UWEKAHUNA GPS benchmark. Bottom plot also 

indicates slow subsidence, relative to HV023, of the leveling 

benchmark HV032 located within 2 km of subsidence center. 

Changes in vertical positions of the GPS benchmarks UWEKAHUNA and SANDHILL shown as solid squares in the 

two plots. 

..... Figure 16. Three-dimensional displacement of two GPS 

stations in the summit area of Kilauea, UWEKAHUNA and 

SANDHILL, relative to LYMAN2. Both stations indicate slow 

subsidence and contraction of summit area, probably the result of 

slow net withdrawal of magma from summit reservoir. 

(/) UWEKAHUNA .... 

s 

Q) 

E 

-33407.7 j -33407.8 

-33407.9 

-33408.0 -1------.-----.---.-------~ 

north 

1987 1988 1989 1990 

~ 

.m -24320.35 j east I 

E -24320.45 ::::: 

a) 

g -24320.55 

0 

(;) ro -24320.65 -1----....---~--.------.r-------l. 

1987 1988 

~ 

1989 1990 

up 

1269.1 

1269.0 

1269.2 j 

1248.9 -1------.-----.---.-------~ 

1987 1988 1989 1990 

~ SANDHILL 

north 

E -36527.5 

2f -36527.6 &:: 

-m -36527.4 j 

-m -36527.7 4----.....-----.--------.-----1 

0 1987 1988 

(/) 

Q) 

g -24807.1 

~ -24806.9 j E -24807.0 

ro m~ 

(;) -24807 '

2 -~----~--.....----1-9-89--.-1 -1-99-0---l 0 1987 1988 

~ .s 1149.8 ...----1-----------. 

Q) 

E 1149.7 

a) 

g 1149.6 

.e (/) 1149.5 -1----.------.--____:=--r-:-.:....:....:....L-.....J 

0 1987 1988 
SURVEY RESULTS 27 

Horizontal movements - GPS Earthquake locations 

APRIL 1987 TO AUGUST 1988 

100mm 

~ 

lOkm 

+ 

+ 

+ 

+ + 

+ 

+ 

+ 

+ ++ 

+ 

+ 

+ 

+ 

AUGUST 1989 TO AUGUST 1990 

100mm ~ 

KULANI MTN~ ACRE 

c:-7J C3> WUNG ~ M~ ~ FERN 

(!SHEI S HULU 

io~ 

lOkm + 

+ 

+ 

+ 

lOkm 

+ 

+ 

++ + 

+ 

+ 

Figure 17. GPS-measured horizontal displacements on Kilauea from April 1987 to August 1988 and from August 1989 to August 

1990. Ellipses represent five times standard error computed using Bemese software package. Earthquake locations for same time periods 

shown at right. 

parameters given in table 11 numnuze, in the leastsquares sense, the difference between measured and modeled horizontal displacement. The measured and modeled 

horizontal displacements are listed in table II and shown 

in figure I8. 

Vertical displacement measured using GPS between August 1988 and August 1989 and computed displacement, 

based on the model derived from horizontal displacement, 

are given in the lower diagram in figure 18. Vertical displacement was also measured along a leveling route that 

was surveyed in February I988 and again in February I990 

(fig. I9). Both GPS and leveling surveys show the same 

pattern of changes and as much as 0.25 m of subsidence, 

though the results of the leveling surveys are more precise. 
28 GLOBAL POSITIONING SYSTEM MEASUREMENTS ON THE ISLAND OF HAWAII FROM 1987 TO 1990 

SUMMIT AREA OF MAUNA LOA VOLCANO 

GPS measurements of Mauna Loa were started in 1988 

with one station in the summit area and another on the west 

+ 

200mm 

---t~ measured 

·········-t> computed 

Elevation changes 

in millimeters 

-20 measured 

[-91 computed 

147 

-79 

[ -1] 

++ _tfO] + 84 

-40d;1-+ [-19] 

+ [-4] ++ 

~111" + -161 

-20 

-72 

[-4] 

[-9] 79 

[-22] 

11 

[2] 

73 [-4] -95 [-38] 

[-1] -t- [-11]~ -57 

14 69 + I" [-121] ,,-P-,jf 

[1] [-1] ~ \ .. -68 

182 --55 "\ -53 [ -71] 

[-3] [-7] [-24] 

+ 

~ 

10km 

~ 

10km 

+ 

Figure 18. Surface displacements from August 1988 to August 

1989 associated with magnitude 6.1 earthquake on June 26, 1989, 

beneath south flank of Kilauea. All displacements are relative to 

LYMAN2. Top: Measured horizontal displacements are shown as 

solid vectors; computed displacements, based on model parameters 

listed in table 11, shown as dashed vectors. Ellipses represent five 

times standard error computed using Bemese software package. 

Surface projection of rectangular sheet model indicated as dashed 

rectangle. Focal mechanism, located at earthquake epicenter, indicates seaward displacement of the upper portion of south flank. 

Bottom: Top numbers are measured vertical changes; bottom numbers in brackets are computed vertical changes based on model 

parameters listed in table 10. 

flank at the 2,700-m elevation. In 1989 and 1990 these two 

stations were remeasured and new stations established on the 

north and the southeast flanks of the volcano. 

Since 1988, the summit station ML1 has moved no 

more than 20 mm horizontally relative to OUO on the 

west flank and less than 50 mm vertically (fig. 20). These 

measured changes are within the accuracy of our surveys, 

and so no significant ground displacement was measured 

using GPS. Results of trilateration measurements made 

across a network that covers the summit area of Mauna 

Loa indicated ML1 moved less than 20 mm between 1988 

and 1990; results of leveling surveys also conducted in the 

summit area show ML1 was raised 0.17 m since the 1984 

155° 20' 155° 10' 155° 00' 154° 50' 

300 

~ 

jB 

Q) 200 

~ .E 100 

ai 

OJ 0 c 

ns 

.r::. 

(.) -100 

c 

0 

+=I 

ns -200 

a> 

w -300 

0 20 40 60 80 100 120 

Distance along leveling route, kilometers 

Figure 19. Comparison of measured and computed vertical 

changes associated with the June 26, 1989, earthquake. Top: 

Location of leveling route and GPS stations used in bottom diagram. Bottom: Elevation changes as function of distance along 

leveling route from Hilo. Results of leveling surveys shown as 

open squares; results of GPS surveys shown as solid squares. 

(Error bars on GPS measurements are five times standard error 

computed using Bernese software package.) Solid line is computed vertical changes based on model parameters listed in table 

11. In bottom diagram, short, dashed line between HULUHULU 

and WUNG RANCH includes local subsidence of summit area. 
Table 11. Model calculations for the June 1989 earthquake. 

Model parameters: latitude 

longitude 

strike angle from north 

dip angle 

north/south 

19.2333 

155.1000 

60° 

so 

depth to the source 

length of the source 

width of the source 

dip-slip displacement 

east/west up/down 

measured, mm model, mm measured, mm model, mm measured, mm 

LYMAN2* 0 0 0 0 0 

KEEAU 0 -14 18 3 -72 

66YY -208 -200 28 11 -221 

APUAPOINT -40 3 14 27 -55 

BM80-1 -85 -28 69 152 -57 

HAWAIIAN ACRES -82 -61 61 15 79 

HAWAIIAN BEACHES -64 -54 21 -17 45 

HILINAPALI -20 7 41 16 69 

HULUHULU** -82 -33 -45 84 -161 

HV07 -42 -11 7 -14 -36 

KAENAPOINT -110 -114 122 84 -53 

KALALUA -268 -248 188 152 -273 

KALOLI-2 -41 -12 -47 -4 11 

KAMAKAIA** 29 7 87 8 14 

KAMOAMOA -191 -200 118 127 -68 

KAPUKAPU 9 9 150 22 182 

KOAE** -53 4 88 17 73 

KULANI -28 -1 -44 9 -79 

MAUNA LOA STRIP -16 3 32 6 147 

MOANAHAUAE -227 -196 176 110 -49 

MOUNTAIN VIEW -24 -26 28 14 -20 

PALl -38 -2 73 43 -95 

SANDHILL** -53 -1 51 23 -111 

UWEKAHUNA ** -38 -3 32 21 -40 

WUNGRANCH -7 -39 71 40 84 

Root-mean-square differences 

(measured minus observed) 31 54 77 

*All displacements, expressed as millimeters, are relative to LYMAN2. 

**These stations were not used to compute the root-mean-square values shown at the bottom. 

6km 

27 km 

12km 

-1.2 m 

model, mm 

0 

-4 

-229 

-7 

-121 

-22 

-20 

-1 

-38 

-3 

-24 

-262 

-2 

1 

-71 

-3 

-1 

-1 

0 

-31 

-9 

-11 

-4 

-4 

-19 

~ -5081 .2 I th I ~ nor Q) 

E 

a) 

(.) 

c: 

--~-

-~ -5081.3 I ~outh , 1 I 

c 1987 1988 1989 1990 

~ 10438.15 

~ 

a) 

(.) 

c: 

ro 

~ 10438.05 

Q) ~ 4081.15 ~----1-----:::---~, 

Q) 

E 

Pi 

c: 

ro 

1ii 

C5 4081.05 __ , 

Figure 20. Three-dimensional position of MLl in summit 

area of Mauna Loa, relative to QUO on west slope of volcano. Dashed horizontal lines indicate no significant changes 

were measured between MLl and QUO during period. 

C/) 

c:: 

~ -< 

C/) 

~ 

c:: 

C3 

C/) 

~ 
30 GLOBAL POSITIONING SYSTEM MEASUREMENTS ON THE ISLAND OF HAWAII FROM 1987 TO 1990 

-26337.7 

~ CAPTAIN COOK north/south 

e 

~ 

cU 

ell 

-26337.8..:: 

-26337.9-:: 

- ~ 

a - -26338.0 - 1

1988 11989 1 1987 1990 

-89190.6 

ell - CAPTAIN COOK east/west 

~ 

e -89190.7-. cU 

a 

~ ell 

-89190.8-:: 

-89190.9 • 1

1988 

~ 

1

1989 1 1987 1990 

495.7 

ell . CAPTAIN COOK vertical 

~ r-H e 495.6-

I1S 

u 

§ 495.5- ell 

a . 

495.4 1

1988 11989 1 1987 1990 

-59795.5 -28712.5 

I MILOLll north/south 

~ KEEl north/south 

- -59795.6 ~ -28712.6..:: - cU 8 . u 

fa -59795.7 E -28712.7-

t;.l ell 

a a . 

-59795.8 -28712.8 

1987 1990 1987 1

1988 

1

1989 11990 

-89347.2 -90619.3 

~ MILOLll east/west ell 

. KEEl east/west 

Q) ~ -89347.3 e e -90619.4-

i cU 

-89347.4 § 

0 

ell 

-89347.5 

1990 

i5 

~ 

ell 

-90619.6 

-90619.5-

. 

1987 

1

1988 

~ 1

1989 

1

1990 

19.6 32.7 

~ MILOLII vertical ell KEEl vertical 

B I Q) 

e 19.5 32.6 

cU I1S u 

§ 19.4 ~ 32.5 ell ell 

0 a 

19.3 32.4 

19 1987 
REFERENCES 31 

eruption of Mauna Loa, though most of the uplift probably occurred before 1986 (Hawaiian Volcano Observatory, 

unpub. data). 

KEALAKEKUA FAULT SYSTEM 

Three stations have been measured annually along the 

southwest coast of Hawaii (fig. 21 ), along a strip that 

encompasses the Kealakekua fault system. This fault system 

on the west flank of Mauna Loa is probably similar in origin 

and operation to the more active and more pronounced Hilina 

Pali fault system along the south flank of Kilauea. Both 

fault systems have arcuate, normal faults that formed during 

sudden seaward displacement of the flank. 

Since 1950, three damaging earthquakes, all believed 

to be greater than magnitude 6.0, occurred along the west 

flank of Mauna Loa (Nakata and others, 1990). Continued 

seismicity at a rate one-quarter to one-half the rate along 

the south flank of Kilauea suggests ground displacement 

may be occurring along the southwest coast of Hawaii. 

MILOLII may have moved seaward as much as 80 

mm between 1987 and 1990. This displacement is consistent with westward slip directions determined by Bryan and 

Johnson (1991) from focal mechanisms beneath this portion of the island. The vertical positions of MILOLII varied greatly, in part because of the inaccuracy of the 1988 

survey and, perhaps, because of an error in measuring the 

antenna height in 1990. Additional measurements will either confirm, or refute, our apparent detection of seaward 

displacement along the west coast of Mauna Loa. 

GPS AS A TOOL TO 

STUDY ACTIVE VOLCANOES 

Most, if not all, volcanic eruptions are preceded by vertical and horizontal displacement of the Earth's surface, often 

occurring near the eventual eruptive site. Kilauea volcano in 

Hawaii is only one of many such examples. Presumably, 

the displacement is a response of the crust to accumulation 

of magma or buildup of pressure within a magma reservoir. 

Measurements made at many different volcanoes show that 

the displacement may precede an eruption by as much as 

several years. Often, a rapid increase in rate of displacement 

occurs a few hours to a few days before the start of eruptive 

activity. Among the challenges of understanding active volcanoes and predicting their eruptions are those associated 

with measuring the displacement of the Earth's surface 

when the amount of displacement is small. 

..... Figure 21. GPS positions of three stations located along 

southwest coast of Hawaii, along the Kealakekua fault system. 

GPS is a new scientific tool that meets this challenge. The ability to record three-dimensional surface displacement at the centimeter level over distances of tens to 

hundreds of kilometers makes GPS ideal in the study of 

active volcanoes. Furthermore, GPS stations can be located in remote and rugged terrain and do not require that 

stations be intervisible. Weather conditions under which 

GPS measurements can be made are less restrictive than 

conventional land-surveying techniques. 

Besides Hawaiian volcanoes, GPS surveys have also been 

conducted at lzu Peninsula, Japan (Shimada and others, 

1990); Yellowstone caldera, Wyoming (Meertens and others, 

1990); Hekla, Iceland (Sigmundsson and others, 1991); 

Mono Craters, California (Marshall and Stein, 1991) and 

Taupo Volcanic Zone, New Zealand (Meertens and others, 

1991). The number of active volcanoes surveyed by GPS 

will continue to grow as ground receivers become less 

expensive and data processing becomes more automatic. 

ACKNOWLEDGMENTS 

We are indebted to the many people who participated 

in the surveys described in this paper. Particular thanks 

goes to M. Sako, A. Miklius, and K. Clark. Work was 

also done by D. Benson, P. Delaney, T. Elias, G. Hamilton, R. Hanatani, K. Honma, J. Kauahikaua, T. Neal, G. 

Punawai, J. Stowell, and K. Yamashita. Also we thank 

the support received from the staff of the Hawaiian Volcano Observatory and the comments and suggestions made 

by R. Stein and P. Segall. 

REFERENCES 

Beutler, G., Bauersima, 1., Gurtner, W., Rothacher, M., Schildkecht, T., Mader G.L., and Abell, M.D., 1987, Evaluation of 

the 1984 Alaska Global Positioning System campaign with 

the Bernese GPS software: Journal of Geophysical Research, 

v. 92, no. B2, p. 1295-1303. 

Bryan, C.J., and Johnson, C.E., 1991, Block tectonics of the island of Hawaii from a focal mechanism analysis of basal 

slip: Bulletin of the Seismological Society of America, v. 81, 

no. 2, p. 491-507. 

Chin, M., 1992, CIGNET report, GPS Bulletin, v. 5, no. 1, Commission VIII, International Coordination of Space Techniques for Geodesy and Geodynamics, National Geodetic 

Survey, Rockville, Maryland, 48 p. 

Davis, J.L., Prescott, W.H., Svarc, J.L., and Wendt, K.J., 1989, 

Assessment of Global Positioning System measurements for 

studies of crustal deformation: Journal of Geophysical Research, v. 94, no. B10, p. 13,635-13,650. 

Decker, R.W., 1987, Dynamics of Hawaiian volcanoes: an overview: U.S. Geological Survey Professional Paper 1350, v. 2, 

Volcanism in Hawaii, edited by R.W. Decker, T.L. Wright, 

and P.H. Stauffer, p. 997-1018. 
32 GLOBAL POSITIONING SYSTEM MEASUREMENTS ON THE ISLAND OF HAWAII FROM 1987 TO 1990 

Decker, R.W., Hill, D.P. and Wright, T.L., 1966, Deformation 

measurements on Kilauea Volcano, Hawaii: Bulletin Volcanologique, v. 29, p. 721-732. 

Decker, R.W., Koyanagi, R.Y., Dvorak, J.J., Lockwood, J.P., Okamura, A.T., Yamashita, K.M., and Tanigawa, W.R., 1983, 

Seismicity and surface deformation of Mauna Loa Volcano, 

Hawaii: Eos, American Geophysical Union, Transactions, 

v.64,no.37,p.545-547. 

Dixon, T.H., 1991, An introduction to the Global Positioning System and some geological applications: Reviews of Geophysics, v. 29, no. 2, p. 249-276. 

Dvorak, J.J., 1990, Geometry of the September 1971 eruptive fissure at Kilauea volcano, Hawaii: Bulletin of Volcanology, 

v. 52, p. 507-514. 

Dvorak J.J., and Dzurisin, D., 1993, Variations in magma-supply 

rate at Kilauea Volcano, Hawaii: Journal of Geophysical Research, v. 98, p. 22,255-22,268. 

Dvorak, J.J., Johnson, C., and Tilling, R.I., 1992, Dynamics of 

Kilauea Volcano: Scientific American, v. 267, no. 2, p. 46-53. 

Dvorak, J.J., Okamura, A.T., English, T.T., Koyanagi, R.Y., Nakata, J.S., Sako, M.K., Tanigawa, W.R., and Yamashita, K.M., 

1986, Mechanical response of the south flank of Kilauea volcano, Hawaii, to intrusive events along the rift zones: Tectonophysics, v. 124, p. 193-209. 

Dzurisin, D., 1992, Geodetic leveling as a tool for studying restless 

volcanoes, in Ewart, J.W., and Swanson, D.A., eds., Monitoring Volcanoes: Techniques and Strategies used by the Staff of 

the Cascades Volcano Observatory, 1980-90: U.S. Geological 

Survey Bulletin 1966, p. 125-134. 

Eaton, J.P., and Murata, K.J ., 1960, How volcanoes grow: Science, 

v. 132, p. 925-938. 

Fiske, R.S., and Kinoshita, W.T., 1969, Inflation of Kilauea Volcano prior to its 1967-1968 eruption: Science, v. 165, 341-349. 

Heliker, C., and Wright, T.L., 1991, The Pu'u O'o-Kupaianaha 

eruption of Kilauea: Eos, Transactions, American Geophysical Union, v. 72, p. 521 and 526. 

Jackson, D.B., Swanson, D.A., Koyanagi, R.Y., and Wright, T.L., 

1975, The August and October 1968 east rift eruptions of 

Kilauea Volcano, Hawaii: U.S. Geological Survey Professional Paper 890, 33 p. 

Jaggar, T.A., and Finch R.H., 1929, Tilt records for thirteen years 

at the Hawaiian Volcano Observatory: Seismological Society 

of America Bulletin, v. 19, p. 38-51. 

Koyanagi, R.Y., Bryan, C.J., Johnson, C.E., Nakata, J.S., and Tanigawa, W.R., 1989, Preliminary evaluation of the 6.1-magnitude Hawaii earthquake of June 25, 1989 and aftershocks: 

Eos, American Geophysical Union, Transactions, v. 70, 

p. 1409-1410. 

Lerch, F.J., Klosko, S.M., Laubscher, R.E., and Wagner, C.A., 

1979, Gravity model improvement using Geos 3 (GEM 9 and 

10): Journal of Geophysical Research, v. 84, no. B8, p. 3897-

3916. 

Lipman, P.W., Lockwood, J.P., Okamura, R.T., Swanson, D.A., 

and Yamashita, K.M., 1985, Ground deformation associated 

with the 1975 magnitude-7.2 earthquake and resulting changes in activity of Kilauea Volcano, Hawaii: U.S. Geological 

Survey Professional Paper 1276,45 p. 

Lockwood, J.P., Dvorak, J.J., English, T.T., Koyanagi, R.Y., 

Okamura, A.T., Summers, M.L., and Tanigawa, W.R., 1987, 

Mauna Loa 1974-1984: a decade of intrusive and extrusive 

activity: U.S. Geological Survey Professional Paper 1350, 

v. 1, Volcanism in Hawaii, edited by R.W. Decker, T.L. 

Wright, and P.H. Stauffer, p. 537-570. 

Macdonald, G.A., Abbott, A.T., and Peterson, F.L., 1983, Volcanoes in the Sea, The Geology of Hawaii: Univ. Hawaii 

Press, Honolulu, Hawaii, second edition, 517 p. 

Marshall, G.A., and Stein, R.S., 1991, Monitoring ground deformation at Mono Craters, California, using a dense GPS network: Eos, American Geophysical Union, Transactions, 

v. 72, no. 44, supplement, p. 118. 

Meertens, C.M., Perin, B., Rocken, C., Blick, G.H., Darby, D.J., 

Otway, P., Scott, B., Williams, R., Wood, P., Van Dissen, R., 

Bennie, S., Walcott, R., Brown, K., Stirling, C., Herries, N., 

and Luo, X., 1991, New Zealand Taupo Volcanic Zone GPS 

project: tectonics, field campaign and near real-time results: 

Eos, American Geophysical Union, Transactions, v. 72, 

no. 17, p. 92. 

Meertens, C.M., Smith, R.B., and Reilinger, R., 1990, The 

Yellowstone crustal deformation experiment: intercampaign 

comparison of the 1987-1989 GPS results from the Yellowstone caldera-Hebgen Lake-Teton fault network: Eos, 

American Geophysical Union, Transactions, v. 71, no. 17, 

p. 478. 

Moore, J.G., 1987, Subsidence of the Hawaiian Ridge, in Decker, R.W., Wright, T.L., and Stauffer, P.H., Volcanism in Hawaii, v. 1: U.S. Geological Survey Professional Paper 1350, 

p. 85-100. 

Nakata, J., Tanigawa, W., and Dvorak, J.J., 1990, Comparison of 

earthquake activity along the west flank of Mauna Loa volcano and the south flank of Kilauea volcano, Hawaii: Eos, 

American Geophysical Union, Transactions, v. 71, p. 1561. 

Okada, Y., 1985, Surface deformation due to shear and tensile 

faults in a half-space: Bulletin of the Seismological Society 

of America, v. 75, p. 1135-1154. 

Okamura, A.T., Dvorak, J.J., Koyanagi, R.Y., and Tanigawa, 

W.R., 1988, Surface deformation during dike propagation: 

U.S. Geological Survey Professional Paper 1463, The 

Puu Oo Eruption of Kilauea Volcano, Hawaii: Episodes 1 

through 20, January 3, 1983, Through June 8, 1984, edited 

by E.W. Wolfe, 165-181. 

Prescott, W.H., Davis, J.L., and Svarc, J.L., 1989, Global Positioning System measurements for crustal deformation: precision and accuracy: Science, v. 244, p. 1337-1340. 

Remondi, B.W., and Hofmann-Wellenhof, B., 1990, GPS broadcast orbits versus precise orbits: a comparison study: Global 

Positioning System: An Overview, Symposium No. 102, edited by Bock, Y., and Leppar, N., Springer-Verlag, New 

York, p. 203-217. 

Schultz, B.E., Ho, C.S., Abusali, P.A.M., and Tapley, B.D., 1990, 

CASA UNO GPS orbit and baseline experiments: Geophysical Research Letters, v. 17, no. 5, p. 643-646. 

Shimada, S., Fujinawa, Y., Sekiguchi, S., Ohmi, S., Eguchi, T., 

and Okada, Y., 1990, Detection of a volcanic fracture opening in Japan using Global Positioning System measurements: Nature, v. 343, p. 631-633. 

Sigmundsson, F., Einarsson, P., Hackman, C., Bilham, R., and 

Thorbergsson, G., 1991, Displacement of GPS control points 

associated with the 1991 Hekla eruption: Eos, American Geophysical Union, Transactions, v. 72, no. 44, supplement, 

p. 115. 
REFERENCES 33 

Swanson, D.A., Duffield, W.A., and Fiske, F.S., 1976, Displacement of the south flank of Kilauea Volcano: the result of 

forceful intrusion of magma into the rift zones: U.S. Geological Survey Professional Paper 963, 39 p. 

Tilling, R.I., and Dvorak, J.J., 1993, Anatomy of a basaltic volcano: Kilauea, Hawaii: Nature, v. 363, p. 125-133. 

Ware, R.H., Rocken, C., and Hurst, K.J., 1986, A Global Positioning System baseline determination including bias fixing 

and water vapor radiometer corrections: Journal of Geophysical Research, v. 91, no. B9, p. 9183-9192. 

Watts, A.B., 1979, On geoid heights derived from Geos 3 altimeter data along the Hawaiian-Emperor Seamount Chain: 

Journal of Geophysical Research, v. 84, no. B8, p. 3817-

3826. 

*U.S. ~ PRIN'J.'IR; OFFICE: 1994-583-048/10004 

Wells, D.E., Beck, N., Delikaraoglou, D., Kleusberg, A., Krakiwsky, E.J., Lachapelle, G., Langley, R.B., Nakiboglu, M., 

Schwarz, K.P., Tranquilla, J.M., and Vanicek, P., 1986, 

Guide to GPS Positioning, Canadian GPS Associates, Fredericton, N.B., Canada. 

Wright, T.L., and Fiske, R.S., 1971, Origin of the differentiated 

and hybrid lavas of Kilauea Volcano, Hawaii: Journal of Petrology, v. 12, p. 1-65. 

Yamashita, K.M., 1992, Single-setup leveling used to monitor vertical displacement (tilt) on Cascades volcanoes, in Ewart, 

J.W., and Swanson, D.A., eds., Monitoring Volcanoes: Techniques and Strategies used by the Staff of the Cascades Volcano Observatory, 1980-90: U.S. Geological Survey Bulletin 

1966, p. 143-149. 



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