GEOLOGICAL SURVEY CIRCULAR 81 0 

The Magnetic Charts of the 

United States for 

Epoch 1975 

The Magnetic Charts of the 

United States for 

Epoch 1975 

By E. B. Fabiano, W. J. Jones, and N. W. Peddie 

GEOLOGICAL SURVEY CIRCULAR 810 

1979 
United States Department of. the Interior 

CECIL D. ANDRUS, Secretary 

Geological Survey 

H. William Menard, Director 

Free on application to Branch of Distribution, U.S. Geological Survey, 1200 South Eads Street, Arlington, VA 22202 
CONTENTS 

Page 

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

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

Procedures. • • • • • . . . . . • • • • • . . • • • • • • • • • . . . • • • • • • • • • • . • • • • • • • • • • • • • • • • • • • • • • • • . • • 1 

Main field data............................................................... 1 

Secular variation data•••••••••••••••••••••••••••••••••••••••••••••••••••••••• 2 

SV analysis for COT48••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 2 

Ma.in field analysis........................................................... 2 

D models for COT48 and Alaska••••••••••••••••••••••••••••••••••••••••••••••••• 3 

Inclination and total intensitY••••••••••••••••••••••••••••••••••••••••••••••• 3 

Model coefficients and final charts••••••••••••••••••••••••••••••••••••••••••• 3 

Evaluation and discussion••••••••••••••••••••••••••••••••••••••••••••••••••••• 3 

Conclusion.................................................................... 4 

References...... . . . . . . • • . . . . . . . . • . . . . . . . . . • • • . • . . . . . . • • . . . . . . • • . . • • • • . • • • . • • • . 7 

APPENDIXES 

A: The number of H and Z survey measurements by one degree tessera within 

the conterminous 48 states•••••••••••••••••••••••••••••••••••••••••••••••• 8 

B: Residuals--U.S. repeat stations and observatories, including Alaskan 

repeat stations .. ••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 11 

C: Coefficients for chart models••••••••••••••••••••••••••••••••••••••••••••• 14 

Figure 1: 

2: 

ILLUSTRATIONS 

Total intensity in the United State for 1975 ••••••••••••••••••••••• 

Comparison of FDOT 1965 and 1975 United States magnetic charts ••••• 

TABLES 

Table 1. Statistics of fit of SV models to initial linear rates of change at 

u.s. repeat stations and observatorieS••••••••••••••••••••••••••••• 2 

2. Main field rms deviations for the one-degree tessera means......... 3 

3. Summary of rms deviations of main field models with subsets of 

survey data using models of n=7•••••••••••••••••••••••••••••••••••• 3 

4. Summary of rms deviations of the fit of models with repeat stations 

and observatories in COT48 and Alaska•••••••••••••••••••••••••••••• 3 

5. Summary of rms deviations of D models to tessera means of 

declination •••••••••••••••••••••••••••••••••• ~ ••••••••••••••••• • • • • 4 

III 

5 

6 
I 
THE MAGNETIC CHARTS OF THE UNITED STATES 

FOR EPOCH 1975 

By E. B. Fabiano, W. J. Jones, and N. W. Peddie 

Abstract 

Approximately 34,000 measurements taken 

from 1900 to 1974 were analyzed by least-squares 

methods to produce a series of five magnetic 

charts of the United States for 1975. A feature 

of the analysis, differing from techniques used 

for previous editions of the national chart, is 

that analytic models define the regional 

magnetic field and are used to contour the 

magnetic charts. 

An overall rms (root mean square) fit of 

less than 235 nT was obtained for the horizontal 

and vertical intensities; for the chart of 

magnetic declination, the rms deviation was on 

the order of 0.5°. The models of annual change, 

derived from data at repeat stations and 

observatories operated by the u.s. Geological 

Survey, yielded an rms deviation of 

approximately 6 nT/yr in the force components 

and 0.7 min/yr in magnetic declination. 

Introduction 

This report describes the method used to 

produce the magnetic charts of the United States 

for 1975, which were published by the U.S. 

Geological Survey in cooperation with the 

National Oceanic and Atmospheric Administration 

(Fabiano and Jones, 1976; Fabiano and others, 

1976; Peddie and others, 1976; Jones and others, 

1976; Fabiano, 1975). The charts are a 

continuation of a series that began with the 

isogonic chart for 1850 and, with a few 

exceptions, have been published at 5- and 1Qyear intervals since then. Deel and Howe (1948) 

and Svendsen (1962) provided historical 

summaries related to the magnetic surveys and 

charts of the United States. In 1975, five 

charts were published: declination (D), 

inclination (I), horizontal intensity (H), 

vertical intensity (Z), and total intensity (F). 

The general objective for these charts was to 

provide the users of geomagnetic data, such as 

surveyors and navigators, with references 

depicting the smoothed distribution of the five 

1 

components of the Earth's magnetic field in the 

region of the United States. A secondary 

objective, related to techniques, was to 

determine if the regional field could be 

adequately modeled using stmple analytic 

expressions which subsequently could be used as 

a convenient means for contouring the isolines 

and also for synthesizing chart values for 

varied user needs. 

Procedures 

The charts for magnetic declination, D, 

are discussed in a later part of this report. 

The following brief outline describes the 

procedures used to obtain the I, H, Z, and F 

charts: 

1. Determine models of current 

secular change for data 

reduction. 

2. Reduce magnetic survey 

measurements of H and Z (taken 

from 1900 through 1974) to epoch 

1975. 

3. Delete from the reduced file those 

measurements which appear to be 

either in error or highly 

anomalous. 

4. Obtain one-degree tessera means of 

H and z. 

5. Perform separate polynomial 

analysis of H and Z for the 

conterminous 48 States region 

(COT48) and for Alaska. For 

Hawaii, copy the results from 

AWC75, the model obtained to 

create the American World Charts 

for 1975 (Peddie and Fabiano, 

1976). 

6. Evaluate and adopt final 100dels; 

prepare magnetic charts. 

Main Field Data 

The initial file of magnetic survey data 

consisted of measurements at 26,097 locations 
within the COT48 region and 8,036 locations in 

Alaska. A record for each location was 

considered acceptable only if both H and Z were 

measured at the station. Some 70 percent of the 

data were measured prior to 1963, and more than 

one-half of the entire file were obtained from 

the airborne surveys conducted by the u.s. Naval 

Oceanographic Office and the Department of 

Energy, Mines and Resources of Canada. Airborne 

survey data now constitute more than 85 percent 

of the survey file measured since 1953. 

The file of measurements obtained from 

1900 to 1962 had been previously reduced for the 

1965 series of magnetic charts. Consequently, 

the reduction procedure for this subset of data 

involved correct ions for the last few years of 

the previous update (1962.5-1965.0) and the 

application of the more recent secular variation 

until the epoch date of 1975.0. Aeromagnetic 

data were corrected to sea level using an 

approximation suggested by Chapman (1951). For 

small heights (h) measured in kilometers, any 

component will be decreased by a fraction h/2123 

of itself at height h. 

To identify and remove what appear to be 

erroneous or anomalous values, residuals were 

computed for each measurement using the world 

magnetic charts model for epoch 1970 (Hurwitz 

and others, 1974) as the reference field and 

1967.5 as the reference date. Data with 

residuals exceeding 800 nT (1,000 nT for Alaska) 

were rejected and, as a result of this screening 

process, 12 percent of the original file was 

omitted from the analysis. 

Appendix A shows the distribution of H and 

Z observations used in obtaining the tessera 

means for the COT48 region. The gaps represent 

the areas where no H and Z measurements were 

available. For Alaska, since one-third of the 

area lacked vector data, values were synthesized 

from AWC75 and used to supplement this file for 

each 2° by 2° gap. 

Because relatively few D measurements had 

been acquired since the last series of D charts, 

published in 1970, the decision was made to 

synthesize one value for each one-degree quad 

from these charts, apply SV (secular variation) 

corrections from 1967.5-1975.0 and then perform 

the least-squares analysis. 

Secular Variation Data 

The file used for the SV analysis consisted 

of three categories of data: 

1. The annual mean values of D, H, 

and Z from Canadian and u.s. 

magnetic observatories. 

2. Vector field measurements at some 

100 repeat stations in COT48, 

which are occupied every 5-7 

years. 

3. Supplemental values of annual 

change, synthesized from AWC75. 

These consisted of values on a 

3° x 3° grid in the ocean 

2 

areas and were included to 

minimize edge effects at the 

chart borders. 

At the time this chart was being compiled, 

no repeat station data since 1965 were available 

on time to perform a regional SV analysis for 

Alaska. Therefore, for Alaska, grid values of 

annual change from AWC75 were used to derive the 

SV polynomial coefficients. (Appendix B lists 

the Alaskan repeat stations which, nevertheless, 

were useful in the subsequent evaluation.) 

SV Analysis for COT48 

For the intervals 1962.5-1967.5 and 

1967.5-1975.0, the linear rates of change for D, 

H, and Z were determined by straight lines 

fitted to the OAM (observatory annual means) and 

the repeat-station measurements. Data were 

reviewed for errors, and on the basis of a 

preliminary analysis, the observatory rates were 

given seven times greater weight than the 

repeat-station rates. 

The function adopted for the least-squares 

procedure is of the form n 1. i . . 

K = .l: .l: a .. (8 -J) (1-J) 1.=o 1.=0 l.J c c ' 

where K is the linear rate of change; n, the 

degree of the polynomial; a 11 , the coefficients 

to be determined; and 9c' -xc' the normalized 

geographic coordinates. For COT48, coordinates 

were nor~lized so that ec = e - 52° and Ac 

= A - 268 • Here, 9 colatitude and A = east 

longitude. 

Analyses were performed for degrees 4 and 6 

(15 and 28 coefficients respectively). On the 

basis of the rms deviations, shown in table 1, 

the latter models were adopted for final use. 

Table I.-Statistics of fit of S V models to initial linear rates of 

change at U.S. repeat stations and observatories 

[SVl, model for 1962.5-1967.5; SV2, model for 1967.5-1975.0. 

Column entries show the rms deviations. Leaders(---) indicate 

no data] 

Degree 

4 

6 

Model 

sv 1 

SV 2 

sv 1 

SV 2 

D 

(min/yr) 

0.8 

.7 

H 

(nT/yr) 

5.2 

s.s 

4.3 

4.7 

Main Field Analysis 

z 

(nT/yq 

6.4 

7.1 

s. 8 

6.4 

Values of H and Z were averaged to obtain 

means for each one-degree tessera, and the data 

were subsequently analyzed using polynomial 

functions of the form described in the section 

entitled "SV Analysis for COT48." Tests were 

run for n=4, 7, and 9, with the objective of 

determining the optimum fit with the fewest 

number of coefficients. Finally, the models for 

n=7 were adopted. 

For Alaska, the analysis presented two 

difficulties: 

1. The data-selection region for Alaska, 

consisting of 2,556 one-degree 
tesserae, contained acceptable H 

and Z data for 1 , 6 7 5 t esse rae, 

only 66 percent of the region. 

2. Because of the chart projections 

used, the COT48 area in the 

northwest overlaps the region 

on the Alaska side of the same 

chart. Since the COT48 and 

Alaskan models were to be 

derived separately, it was 

necessary to insure that the 

models were consistent in the 

region of overlap. 

Consequently, fill-in grid values were 

synthesized from the AWC75 model for the 

sparsely surveyed region and from the COT48 

models of H and Z in the overlap area. This 

amalgamated data set for Alaska, consisting of 

both sets of synthesized values and the onedegree tessera means, was then analyzed to 

produce degree-7 polynomial models for H and Z, 

using colatitude 32° and east longitude 205° to 

normalize the coordinates. 

D Models for COT48 and Alaska 

The COT48 region was partitioned into five 

areas, each consisting of 12-degree longitudinal 

bands. Separate analyses, degrees 4 and 7, were 

performed for each band, allowing for 2-degree 

longitudinal overlaps at the partition 

boundaries to minimize edge-effect distortions. 

For Alaska, a single model n=7 for the 

entire region was obtained from values 

synthesized and updated from the 1970 Alaska 

magnetic chart (U.S. Department of Commerce, 

1970) and additional fill-in values from the 

COT48 and AWC75 models. 

Inclination and Total Intensity 

The charts of I and F were derived from 

the H and Z models using the formulas 

I =arctan Z/H and F = (H2 + z2)1/2 

The annual change rates, i and F, were computed 

from the first derivatives, where 

Model Coeificients and Final Charts 

The coefficients for the components D, H, 

and Z, shown in Appendix C, was subsequently 

used to contour the five magnetic components. 

Where required, near the chart borders, isolines 

were manually adjusted to merge with the 

corresponding isolines of the American World 

Magnetic Charts for 1975. Consequently, we 

recanmend that for synthesizing values from the 

analytic models, one should use the American 

World Charts for ocean areas 200 km beyond the 

U.S. coastlines. 

3 

Evaluation and Discussion 

Tables 2, 3, and 4 sununarize the major 

statistics pertinent to the evaluation of the 

models. In table 2, the lower rms deviations 

shown for degree 7 are what one may anticipate 

from an analysis of averaged values. 

In table 3, the adopted models for degree 

7 are compared to the survey data file. The 

slightly larger rms deviations for COT48 column 

A (compared to column B) probably result from 

the fact that A contains the older data. 

However, the differences are not large and are 

within the probable error limits for measured 

data. Both tables suggest that. the COT48 and 

Alaska charts have comparable accuracies. 

The most recent data available for 

determining the quality of the fit to the models 

are the vector measurements at the magnetic 

observatories and repeat stations for the 

interval 1971-74. The residuals for these 

stations, shown in Appendix B, are applicable 

for the epoch date of the measurement indicated 

in the last column; the summarized statistics 

are shown in table 4. 

Measurements from repeat stations and 

observatories represent the most reliable survey 

data available. By comparison with other 

measurements, they are only marginally affected 

by temporal and transient variations and 

generally the stations are located in 

nonanomalous regions. As a result, these 

corresponding rms fits are quite good and serve 

to substantiate the rms fits shown in tables 2 

and 3. 

Table 2.-Main field rms deviations, in nanoteslas, for the one-degree 

tessera means (units ofnT) 

Degree -------

Component: 

H 

z 

4 

156 

152 

COT48 

118 

130 

9 

116 

128 

Alaska 

115 

148 

Table 3.-Summary of rms deviations of main field models with subsets 

of survey data using models ofn=7 (units ofnT) 

A B 

COT48 

Component (Every 5th value, 

1900-74) 

H 188 

z 226 

Number of values 4,409 

(All values, 

1939-74) 

188 

197 

15,420 

c 

Alaska 

(All values, 

1900-74) 

184 

234 

7,881 

Table 4.-Summary ofrms deviations of the fit of models with data 

from repeat stations and observatories in COT48 and Alaska 

[COT48, 113 stations; Alaska, 26 stations] 

Component COT48 Alaska 

D 0.37° 0.52° 

H 145 nT 106 nT 

I 0.18° 0.13° 

z 225 nT 184 nT 

F 205 nT 174 nT 
Table 5 refers to the partitioning scheme 

and related statistics for the D models of 

COT48. Because the values analyzed are scaled 

from a smooth chart, the overall fit, as one 

might anticipate, is remarkably close, to within 

6 minutes of arc for most partitions, providing 

some evidence for the adequacy of the modeling 

process for regions as large as 2 million square 

kilometers--the approximate size of each 

partitioned area. The larger rms values in 

bands 2 and 3 probably indicate the numerous 

declination anomalies in the Great Lakes region. 

Table 5.-Summary ofrms deviations of D models to tessera means of 

declination 

[ 'Y column shows the east longitude normalizing factor I 

Partition rms {in degrees2 

Band 0 W. long Degree y 

4 7 {in degrees2 

1 66-77 0.11 0.01 289 

2 78-89 0 18 .14 277 

3 90-101 0 14 .10 265 

4 102-113 .08 .06 253 

5 114-125 .06 .OS 241 

The D models were also evaluated by 

comparing them to two subsets of survey data. 

The first set consisted of 1,450 station values, 

updated to 1975.0 and randomly distributed 

within COT48. From these measurements, an 

overall rms of 0. 50° was determined. The second 

subset, comprising survey data excluded from the 

file of analysis data, consisted of 287 airborne 

measurements from the Project Magnet surveys 

made from 196 7 to 1970. With this set, the 

computed rms was 0.52°. 

Among the reasons for the lack of fit that 

one may observe from the differences which exist 

between the data and models, the following 

should be noted: 

1. Errors in the data. This problem 

was discussed earlier. Wherever 

possible, it is important to 

determine whether the errors are 

random or systematic. Hannaford 

and Haines (1969), for example, 

reported probable errors in 

aeromagnetic data of 0.4° in D, 

40 nT in H, and 70 nT in z. In 

the older land survey data, Deel 

and Howe (1948) reported possible 

errors as large as 150 nT in the 

computed value of Z due to 

instrumental uncertainties. 

2. Secular variation. The secularvariation estimates for the 

earlier years, especially prior 

to the 1930's, are less reliable, 

due primarily to insufficient data 

as well as to the quality of the 

instrumentation. In addition, the 

use of linear SV estimates, though 

4 

convenient and in some instances 

practical, introduces errors in 

data reduction because the SV is 

not necessarily linear. This is 

not a serious problem for datareduction intervals of a few years. 

However, for a 5- or 10- year 

interval, significant errors could 

accumulate. 

3. Local and regional anomalies. It is 

difficult at this time to assess the 

impact resulting from the local and 

regional magnetic anomalies on the 

statistics relating to the fit of 

the data to the model. If, for 

example, one had available up-todate vector measurements spaced 

a few kilometers apart nationwide, 

relatively accurate assessments of 

the "normal" and anomalous fields 

could be made. To date, however, 

the available vector data are too 

poorly distributed, both in space 

and in time. 

A small-scale chart of total intensity and its 

annual change for 1975 in the United States is 

shown in figure 1. This chart was adapted from 

the 1975 U.S. total intensity chart (Fabiano and 

others, 1976). Figure 2 illustrates how SV 

estimates of total intensity (FOOT) can change 

over a 10-year period. Note that at latitude 

45° and longitude 90° the estimated rates of SV 

differ by more than 60 nT/yr. 

Conclusion 

The various statistics of fit presented 

indicate that the polynomial technique is 

generally adequate for producing models of the 

smoothed field suitable for national reference 

charts. The major deterrent for obtaining mre 

reliable models appears to lie not so much in 

technique as it does in the accuracy of the 

available data base. 

Dependence on these data may soon be 

minimized and perhaps eliminated as a result of 

two magnetic surveys, one completed and the 

other planned. During 1977-78, the u.s. Naval 

Oceanographic Office completed a vector survey 

of the United States with north-south tracklines 

flown at approximately lOQ-km spacing; several 

east-west lines were also flown. In 1979 the 

National Aeronautics and Space Administration in 

cooperation with the U.S. Geological Survey will 

launch MAGSAT, a low-level satellite which will 

obtain worldwide vector data. The acquisition 

of measurements from both sources will 

substantially improve the data base used for 

future national charts. 
Vt 

00' 

I ------ ~ ~ I ~4±_22_-=---- I lL~CC:::::: I I"~ 

.Jo·--------

Albers (qu•l Are• PruieCiton 

I 

SCAl£ 1 17,000,000 

0 100 •oo II!LU 

I 

.Jo. 

F- ~ 

L 

,~ ___ :.__-:i:-..:::::.-:-_?1 tOOilii.OIIIiTtJIJ 

--------------- j 

Figure 1. Total Intensity in the United States for 1975. (Solid lines are field contours in units of nanotesla (nT); 

dashed lines are annual change contours in units of nT/yr.) 
r/ 

I 

•o·~ 

(J'\ 

to·-----. 

-- ~ 

Annual change in F (1965 U.S. Chart$) 

AA!nuol change in F (1975 U.S. Charts) 

~ 

.l•"'"" 

..\l~rifqu•IArto•ProJ«IIon 

SCALE I 17.000.000 

0 ... JOO 400 IIIIL(S 

~loo- ~.;- - --~ .00- ~-~~i-i: 

Jo· 

Figure 2. Comparison of FDOT 1965 and 1975 United States magnetic charts (in units of nT/yr.) 

----- - ,o·, 

_....-l". 

-

I 

I 

! 
References 

Chapman, Sydney, 1951, The earth's magnetism, 

(2d ed.): New York, John Wiley, p. 27. 

Deel, S. A. , and Howe, H. H., 194 8, United 

States magnetic tables and magnetic charts 

for 1945, u.s. Coast and Geodetic Survey 

Serial 667: u.s. Government Printing Office, 

Washington, D.c., p. 10-12. 

Fabiano, E. B., 1975, Magnetic declination in 

the United States, epoch 1975.0: u.s. 

Geological Survey Miscellaneous Geologic 

Investigations Map I-911. 

Fabiano, E. B., and Peddie, N. w., 1975, U.S. 

world chart model coefficients for 1975: 

American Geophysical Union Transactions, v. 

56, no. 9, p. 587-588. 

Fabiano, E. B., and Jones, w. J., 1976, Magnetic 

horizontal intensity in the United States, 

epoch 1975.0: U.S. Geological Survey 

Miscellaneous Geologic Investigations Map I913. 

Fabiano, E. B., Peddie, N. w., and Jones, w. J., 

1976, Magnetic total intensity in the United 

States, epoch 1975.0: U.S. Geological Survey 

Miscellaneous Geologic Investigations Map I915. 

Hannaford, w., and Haines, G. V., 1969, A threecomponent aeromagnetic survey of the Nordic 

countries and the Greenland sea: Dominion 

7 

Observatory Publications, Ottawa, v. 37, no. 

5, P• 113-164. 

Huritz, Louis, Fabiano, E. B., and Peddie, N. 

w., 1974, A model of the geomagnetic field 

for 1970: Journal of Geophysical Research, 

v. 7 9, no • 11 , p • 1 716 -1 71 7. 

Jones, w. J., and Fabiano, E. B., 1976, Magnetic 

vertical intensity in the United States, 

epoch 1975.0: U.s. Geological Survey 

Miscellaneous Geologic Investigations Map I914. 

Peddie, N. w., and Fabiano, E. B., 1976, A model 

of the geomagnetic field for 1975: Journal 

of Geophysical Research, v. 81, no. 14, p. 

2539-2542. 

Peddie, N. w., Jones, w. J., and Fabiano, E. B., 

1976, Magnetic inclination in the United 

States, epoch 1975.0: u.s. Geological 

Survey Miscellaneous Geologic Investigations 

Map I-912. 

Svendsen, K. L., 1962, United States Magnetic 

Tables for 1960, U.S. Coast and Geodetic 

Survey Publication 40-2: U.S. Government 

Printing Office, Washington, D.C., 91 P• 

U.S. Department of Commerce, 1970, Isogonic 

chart of the United States, 1970: u.s. Dept. 

of Commerce, Environmental Science Services 

Administration, chart no. 3077. 
Appendix A.--The number of H and Z survey measurements by one-degree tessera within the conterminous 48 States 

[Latitude and longitude, in degrees, are shown in the extreme left-hand column and top row, respectively] 

-130 -129 -128 -127 -126 -125 -124 -123 -122 -121 -120 -119 -118 -117 -116 -115 -114 -113 -112 -111 -110 -109 -108 -107 -106 

56 

55 

54 

53 

52 

51 

50 

49 

48 

47 

46 

45 

44 

43 

42 

41 

40 

39 

38 

37 

36 

35 

34 

33 

32 

31 

30 

29 

28 

27 

26 

25 

24 

23 

22 

21 

20 

9 6 6 6 9 4 10 15 17 21 12 11 8 9 9 15 4 8 

9 

5 

6 

13 

11 

12 

10 

4 

0 

6 

0 

4 

8 

5 

4 

11 

13 

4 

14 

8 

4 

0 

0 

0 

0 

0 

12 

10 

14 

11 

15 

12 

13 

4 

0 

4 

0 

4 

5 

8 

20 

10 

0 

8 

9 

0 

0 

0 

0 

3 

14 

3 

14 

12 

17 

13 

4 

0 

5 

0 

0 

1 

8 

5 

13 

24 

1 

13 

0 

0 

0 

0 

0 

12 

11 

6 

20 

8 

12 

6 

0 

6 

6 

4 

6 

1 

4 

9 

23 

14 

14 

0 

1 

0 

0 

1 

0 

14 

4 

8 

9 

13 

13 

8 

6 

39 

10 16 

4 

8 

9 8 

9 

10 

11 

0 14 

16 

32 

9 

4 

18 

0 

0 

0 

0 

0 

0 

14 

11 

25 

32 

15 

6 

14 

11 

8 

0 

0 

0 

0 

0 

4 

6 

16 

15 

10 

8 

27 

32 

0 

6 

12 

20 

8 

4 

16 

14 

43 

10 

4 

13 

6 

13 

0 

4 

0 

0 

0 

1 

10 

9 

13 

17 

14 

17 

63 

18 

16 

8 

63 

11 

4 

18 

12 

0 

0 

0 

0 

11 

13 

12 

20 

22 

4 

0 

13 

6 

12 

22 

18 

11 

13 

8 

1 

4 

9 

0 

4 

0 

0 

0 

8 

12 

8 

10 

23 

9 

8 

8 

6 

0 

4 

13 

22 

12 

17 

15 

6 

13 

11 

1 

5 

0 

8 

0 

6 

0 

0 

0 

0 

10 

8 

9 

19 

21 

8 

4 

4 

4 

0 

4 

19 

13 

24 

10 

16 

19 

18 

6 

4 

4 

8 

6 

0 

5 

0 

0 

19 

18 

21 

15 

12 

12 

12 

11 

4 

15 

5 

0 

11 

13 

31 

4 

17 

36 

4 

11 

6 

0 

4 

0 

0 

8 

17 

20 

6 

11 

13 

17 

11 

6 

0 

15 

14 

14 

22 

24 

11 

38 

11 

13 

10 

17 

9 

4 

9 

1 

0 

0 

17 

18 

17 

11 

9 

8 42 

13 

13 

12 

6 

0 

18 

8 

0 

0 

12 

11 

12 

10 

5 

14 

9 

18 

6 

6 

4 

5 

6 

0 

0 

4 

9 

22 

11 

4 

1 

0 

0 

4 

0 

0 

10 

19 

16 

12 

20 

1 

4 

5 

13 

4 

17 

14 

14 

7 

6 

7 

0 

16 

25 

22 

36 

16 

11 

6 

0 

0 

15 

10 

14 

13 

16 

4 

6 

15 

4 

8 

8 

8 

4 

4 

0 

87 19 

26 16 

35 

21 

34 

28 

18 

11 

0 

12 

12 

15 

17 

1 

18 

4 

6 11 

0 

12 

11 

12 

22 

0 

4 

6 

4 

9 

4 

6 

11 

10 

6 

0 

16 

4 

14 

20 

13 

9 

12 

8 

6 

10 

4 

9 

8 

9 

5 

10 

10 

14 

9 

21 

11 

13 

0 

0 

8 

4 

18 

27 

12 

13 

14 

0 

4 

6 

9 

8 

10 

8 

6 

6 

20 

12 

6 

37 

21 

6 10 

22 

14 

9 

4 

0 

1 

16 

14 

16 

17 

0 

4 

10 

60 

13 

4 

10 

9 

21 

1 

6 

4 

8 

0 

10 

12 

15 

6 

3 

0 

12 

22 

2 

9 

21 

0 

4 

8 

6 

0 

6 

12 

6 

6 

3 

10 

35 

11 

19 

4 

9 

1 

1 

9 

4 

4 

17 

12 

8 

20 

4 

6 

0 

0 

6 

4 

4 

4 

6 4 

11 

26 32 

18 

20 

11 

0 

0 

12 

13 

9 

12 

25 

1 

4 

4 

11 

5 

0 

10 

6 

11 

28 

8 

10 

0 

1 

11 

11 

20 

10 

10 

21 

11 

9 

4 

4 

19 

0 

10 

1 

12 

6 

9 

0 
Appendix A.--The number of H and Z survey measurements by one-degree tessera within the conterminous 48 States--Continued 

-106 -105 -104 -103 -102 -101 -100 -99 -98 -97 -96 -95 -94 -93 -92 -91 -90 -89 -88 -87 -86 -85 -84 -83 -82 

56 

55 

54 

53 

52 

51 

50 

49 

48 

47 

46 

45 

44 

43 

42 

41 

40 

39 

38 

37 

36 

35 

34 

33 

32 

31 

30 

29 

28 

27 

26 

25 

24 

23 

22 

21 

t20 

8 

24 

21 

0 

7 

29 

24 21 

13 16 

13 10 

8 

18 

1 

0 

4 

10 40 

14 

16 

14 

8 

16 19 

23 

5 

6 

10 

30 

11 

9 

8 

10 13 

4 

24 

14 

14 

4 

13 

4 

14 

20 

15 

22 

15 

4 

4 

17 

14 

17 

28 

18 

21 

11 

0 

5 

4 

13 

23 

10 

13 

30 

6 

8 

8 

6 

9 10 10 8 

4 

0 

0 

0 

4 

0 

0 

5 

7 

6 

1 

0 

1 

3 • 

5 

0 

0 

12 

6 

0 

0 

4 

0 

4 

12 

0 

0 

1 

0 

4 

5 

4 

13 

8 

12 

21 

20 

15 

30 

14 

6 

5 

0 

8 

6 

19 

11 

9 

28 

4 

17 

6 

8 

15 

8 

0 

6 

4 

5 

4 

6 

11 

15 

6 

6 

9 

17 

26 

21 

10 

4 

6 

6 

11 

19 

13 

8 

37 

12 

8 

12 

6 

8 

6 

1 

4 

6 

14 

5 

6 

9 

20 

31 

9 

6 

11 

9 

22 

10 

6 

22 

9 

12 

13 

10 

13 

8 

8 

7 

19 

1 

7 

4 

1 

6 

17 

6 

4 

6 

4 

16 

39 

17 

4 

12 

22 

9 

4 

10 

23 

18 

8 

37 

12 

11 

23 

8 

9 

8 

10 

4 

0 

12 

9 

22 

9 

32 

44 

17 

4 

7 

8 

14 

12 

23 

16 

39 

9 

4 

30 

21 

10 

4 

21 

5 

8 

8 

11 

24 

27 

9 

11 

21 41 

8 14 

19 22 

11 

8 

13 

4 

15 

17 

17 

11 

9 

12 

16 13 

22 

12 

11 

29 

10 

0 

0 10 

6 

4 

11 

8 

17 

13 

7 

9 

16 16 

6 

6 

9 

31 

5 

6 

10 

15 

7 

32 

22 

22 

69 

23 

20 

14 

11 

11 

9 

6 

9 

14 

5 

4 

12 

4 

1 

14 

9 

11 

11 

9 

10 

36 

16 

9 

9 

12 

10 

19 

25 

23 

9 

23 

10 

15 

16 

18 

9 

14 

2 

2 

9 

6 

2 

2 

7 

9 

10 

8 

1 

0 

28 

8 

3 

2 

9 

18 

12 

29 

9 

0 

12 

15 

19 

28 14 

25 

10 

12 

21 

14 

19 

15 

9 

8 

8 

10 

29 

31 

20 

14 

11 

23 

19 

26 

28 

13 

15 

21 

21 

15 

29 

23 

26 44 

17 

10 9 

6 18 

8 

15 

19 

2 

9 

4 

0 

7 

4 

7 

18 

15 

19 

15 

0 

10 

0 

0 

4 

4 

12 

14 

9 

13 

9 

13 

9 

19 

11 

4 

8 

0 

0 

0 

6 

0 

2 

10 

8 

4 

8 

10 

0 

5 

8 

6 

8 

6 

10 11 

0 

13 

4 

14 

16 48 

18 

20 

33 

26 

21 

0 

13 

4 

15 

17 

4 

18 9 

6 11 

16 

8 

12 

14 

24 

30 

5 

4 

6 

0 

8 

15 

25 

21 

10 

5 

11 

6 

14 

19 

17 

4 

2 

3 

5 

8 

14 

4 

27 

8 

5 

24 

37 

24 

10 

12 

6 

8 

10 

1 

6 

6 

6 

1 

4 

5 

8 

6 

11 0 

12 10 20 

18 16 

11 

29 

12 

6 

34 

6 

36 

31 

14 

10 

14 

18 12 

26 

i7 

9 

13 

15 

13 

11 

19 

17 

13 

20 

25 

10 

12 

6 

11 

14 

6 

8 

11 

16 

35 

6 

4 

16 

36 

8 

26 

29 

19 

11 

24 

28 

15 

16 

18 

20 

30 

25 

29 

16 

19 31 41 41 

22 

40 

37 49 40 

34 44 27 

24 

23 

8 

8 

8 

19 20 

9 15 

25 

20 11 

14 

18 

20 

17 

14 

6 

0 

0 

1 

4 

0 

0 

20 11 

14 

13 

1 

0 

4 

0 

1 

4 

15 

24 

1 

o. 

2 

1 

1 

0 

5 

4 

11 

16 

15 

13 

18 

18 

17 

15 

0 

4 

4 

0 

4 

4 

8 

15 

12 

19 

35 

18 

20 

9 

8 

1 

9 

8 

12 

9 

1 

5 

9 17 

31 43 

14 

19 

23 

24 

12 

11 

12 

6 

5 

9 

8 

13 

4 

5 

4 

18 

30 

15 

37 

15 

18 

28 

6 

7 

6 

6 

13 

0 

1 

1 

4 

25 

19 

42 

28 

34 

20 

14 

13 

5 

8 

1 

0 

9 

11 

0 

1 

18 

34 

35 

15 

22 

16 

22 

14 

21 

16 

10 

9 

2 

10 

29 

5 

0 

0 
Appendix A.--The number of H and Z survey measurements by one-degree tessera within the conterminous 48 States--Continued 

-82 -81 -80 -79 -78 -77 -76 -75 -74 -73 -72 -71 -70 -69 -68 -67 -66 -65 -64 -63 -62 -61 -60 

56 

55 

54 

53 

52 

51 

50 

49 

48 

47 

46 

45 

44 

43 

42 

41 

40 

39 

38 

37 

36 

35 

34 

33 

32 

31 

30 

29 

28 

27 

26 

25 

24 

23 

22 

21 

20 

5 

9 

6 

9 

22 

8 

13 

24 

2 

8 

4 

11 

8 

8 

7 

9 

7 

10 12 

24 

6 

26 

17 

38 

36 

4 

6 

4 

9 

12 

33 

8 

5 

3 

6 

7 

8 

18 

7 

10 

4 19 

8 

11 11 

11 

1 

6 

9 

5 

5 

11 

18 

18 

8 13 

12 

0 

5 

12 

17 

15 

14 

20 

13 

17 

18 

12 

15 

13 

13 

12 

0 

3 

2 

7 

12 

4 

7 

4 

9 

14 

13 

9 

9 

12 

4 

14 

1 

8 

25 

12 0 27 

28 44 15 

10 

8 

9 

4 

12 

7 

16 

26 

10 

7 

4 

10 

6 

13 

39 

32 

6 

10 11 

14 

15 

14 

23 

80 

17 25 18 67 37 33 41 17 

14 

15 

21 

11 

23 

20 22 

10 

20 

18 

6 

25 

16 17 

39 

35 

17 

27 

24 

42 

28 

24 

15 

17 

29 

10 

8 

14 

10 

40 

8 

1 

5 

0 

35 

24 

34 

12 

32 

18 

16 

13 

0 

9 

33 

12 

18 

11 

6 

0 

10 

0 

9 

10 

13 

34 

27 

65 

18 

19 

32 

16 16 32 

8 20 

14 

6 

24 

5 

10 

11 

34 

34 47 

38 41 

22 

12 

31 

24 

84 

19 

23 25 46 

22 23 

6 23 

10 10 15 

13 

11 

6 

7 

11 

14 

8 

6 

3 

0 

2 

4 

6 

0 

0 

4 12 

8 11 

1 13 7 

0 

1 

4 

0 

0 14 

0 

0 

4 

0 

0 

0 

7 

7 

4 

13 

4 

5 

4 

6 

3 

0 

4 

20 24 45 15 

11 6 7 29 

6 

12 

6 23 28 41 

14 19 58 

28 55 34 18 

71 27 

9 

7 

20 18 10 

10 22 20 

16 17 13 

29 

15 

11 

11 

6 

8 

14 

9 

9 14 

4 

8 

9 

10 

0 14 

6 

6 

9 

17 

15 

0 

11 

10 

23 

8 

5 

6 • 10 

7 

4 

4 

0 

11 

53 

9 

11 

9 

17 

10 

0 

6 

12 

10 

6 

13 

7 

0 

0 

9 

5 

4 

0 

7 

0 

8 

5 

8 

9 

13 

6 11 

10 

16 

8 14 

6 10 

4 

5 

4 

{) 

4 

14 

29 15 

18 

5 

6 

4 

18 

13 

6 

7 

4 

6 

6 

13 

14 

4 

7 

24 

12 

4 

8 

0 

0 

7 

10 11 

7 

6 

0 

6 

28 

18 

3 

0 

26 

31 43 

5 17 

10 

33 

12 

16 

8 

6 

6 

9 

18 

10 

0 

0 

8 

8 

8 

19 

9 

7 

4 

15 

12 

10 13 

9 

9 

13 

10 

20 

5 

15 

6 

0 

6 

12 

11 

10 

0 13 

20 11 10 

16 

20 

20 

8 

7 

6 

4 

0 

2 

0 

3 

4 

6 11 

7 4 

7 4 

0 12 

11 

7 

4 

6 

12 

8 

16 

4 

0 

11 

7 

16 

16 

9 

7 

16 19 

6 

11 

9 

33 

11 10 15 

5 

8 

24 34 

31 

6 

12 

32 

23 

4 

12 

33 

18 30 12 

12 

8 

4 

21 

13 

12 

8 

4 

7 

6 

16 29 

6 

8 

0 

1 

0 

3 

0 

15 

37 

8 

10 

10 

9 

5 

0 

29 17 

18 22 

46 

6 

8 

1 

5 

13 

0 

4 0 

10 

9 14 

14 

0 21 1 

8 

14 

11 

8 

16 15 

11 

7 

14 

0 

19 226 36 

10 

4 

2 

21 

19 

10 

8 

11 

11 

9 

8 

6 

8 

5 

11 

4 

9 

0 

7 

0 

14 

8 

8 

11 

11 

8 

14 

13 

14 

14 

9 16 

6 13 

7 7 

12 

9 

4 

11 

6 

9 

5 

14 

0 

4 

4 

0 

0 

7 

8 

0 

6 10 

12 

16 

6 

9 

8 

1 

4 

4 

9 

4 

0 

0 

11 

27 

9 

17 

22 

11 11 

6 

13 

9 

3 

4 

0 

11 

17 

18 

11 

4 

7 

4 

0 

0 

1 

10 

10 

8 

9 

11 

10 

5 

6 

9 

8 

8 

8 

7 

12 

8 

3 

4 

4 

7 

4 

1 

0 

0 

9 

10 
Appendix B.--Residuals--u.s. reEeat stations and observatories 1 including Alaskan reEeat stations 

[Station value minus model value for the date of measurement; for example, 19 71. 4 = 71. 4; 

Lat, latitude; Long, longitude; Decl, declination; Horiz, horizontal; Vert, vertical; 0 degrees; nT, nanotesla] ' 

State Station (name) Lat Long Decl Dip Horiz Vert Total Date 

{Abbr~ 0 0 0 0 nT nT nT 

AL--- Marion (FISH)--------- 32.73 -87.28 -0.20 0.08 121. 421. 431. 71.4 

AL---- Marion (FISH)--------- 32.73 -87.28 -0.21 0.09 98. 392. 395. 72.9 

AL---- Gadsden--------------- 34.00 -86.00 0.04 -0.14 226. 179. 258. 74.4 

AZ---- Nogales--------------- 31.35 -110.94 0.12 -0.09 -9. -164. -144. 72.9 

AZ---- Phoenix--------------- 33.46 -111.96 0.33 -0.05 -44. -161. -161. 72.8 

CA---- Bishop---------------- 37.36 -118.36 -0.45 0.03 -17. 20. 10. 7 2.8 

CA---- Lompoc---------------- 34.64 -120.53 0.29 0.22 -203. 36. -73. 72.7 

CA---- San Diego (CAMP ELL2)- 32.89 -117.07 0.42 0.17 172. 556. 564. 72.8 

CA---- San Diego (MIRAMAR)--- 32.84 -117.16 -0.54 0.60 -178. 709. 512. 72.8 

CA---- San Francisco (1952)-- 37.72 -122.49 0.15 -0.05 29. -43. -24. 7 2. 7 

CA---- San Francisco (GOLF)-- 37.72 -122.49 0.25 -0.20 125. -144. -67. 72.7 

co---- Cortez (ARPT)--------- 37.30 -108.63 -0.48 0.17 -201. -61. -142. 73.8 

FL---- Fort Meyers----------- 26.61 -81.88 -0.36 o. 01 27. 61. 66. 71.4 

FL---- Fort Meyers----------- 26.61 -81.88 -0.30 0.07 -40. 47. 19. 74.3 

FL---- Key West (RK PT)------ 24.56 -81.68 -0.20 0.16 -109. 87. 12. 71.3 

FL---- Key West (GOLF)------- 24.57 -81.74 -0.19 0.19 -128. 101. 13. 71.3 

FL---- Key West (GOLF) Aux-2- 24.57 -81.74 -0.18 0.30 -236. 92. -55. 74.3 

FL---- Spruce Creek (TEL)---- 29.07 -81.05 0.15 0.54 -289. 477. 279. 71.4 

FL---- Spruce Creek (A)------ 29.08 -81.03 0.09 0.49 -263. 438. 258. 71.4 

FL---- Spruce Creek---------- 29.07 -81.05 0.08 0.51 -305. 391. 195. 74.3 

GA---- Bainbridge (1958) ----- 30.91 -84.60 -0.12 -0.13 84. -105. -54. 71.4 

GA---- Bainbridge (1958)----- 30.91 -84.60 -0.15 -0.14 56. -166. -121. 74.3 

GA---- Milledgeville--------- 33.09 -83.28 1.11 -0.04 -77. -246. -255. 71.4 

GA---- Waycross-------------- 31.24 -82.35 0.03 -0.14 104. -82. -25. 74.3 

ID---- Weiser---------------- 44.26 -116.97 0.41 0.03 98. 318. 332. 73.8 

IL---- Joliet (CC 2)--------- 41.50 -88.05 0.26 -0.10 65. -114. -87. 72.4 

IL---- Joliet (WDRF) --------- 41.54 -88.01 0.09 0.01 11. 51. 52. 72.4 

IA---- Indianapolis---------- 39.73 -86.28 -0.47 o.oo -43. -118. -126. 72.4 

KY---- Lexington (CC)-------- 38.08 -84.45 0.57 0.46 -542. -141. -326. 73.6 

ME---- Bangor (BROADWAY)----- 44.83 -68.79 -0.14 0.09 -87. 36. 8. 73.5 

ME---- Bangor (GRIFFIN)------ 44.83 -68.81 -0.12 0.08 -74. 41. 17 0 73.5 

ME---- Fort Kent (B HOSP)---- 47.27 -68.60 -0.19 0.03 -5. 91. 86. 73.6 

ME---- Fort Kent (PASTURE)--- 47.25 -68.59 -0.20 0.06 -38. 102. 88. 73.6 

MI---- Detroit (PARK)-------- 42.36 -83.26 -0.09 -0.22 155. -236. -178. 72.5 

MI---- Detroit (RR)---------- 42.34 -83.25 -0.01 -0.22 143. -272. -215. 72.5 

MI---- Marquette (GF2 197 2)-- 46.54 -87.42 0.82 0.01 -56. -170. -178. 72.5 

MO---- Rolla (EAST)---------- 37.95 -91.78 -0.45 o.oo 31. 88. 93. 73.7 

MS---- Brooklyn-------------- 31.03 -89.17 -0.04 -0.07 26. -93. -70. 72.9 

MS---- Grenada (A)----------- 33.75 -89.80 -0.24 o.oo 72. 160. 175. 72.9 

MS---- Granada (71)---------- 33.75 -89.80 -0.24 0.02 63. 166. 177 0 72.9 

MS---- Lamar (B GUM)--------- 30.92 -89.39 0.06 -0.06 21. -79. -60. 72.9 

MT---- Billings (PP)--------- 45.79 -108.53 -0.72 -0.04 81. 113. 132. 72.5 

MT---- Glendive (ARPT 71)---- 47.13 -104.81 -0.17 o.oo -14. -36. -38. 71.6 

MT---- Havre----------------- 48.56 -109.72 0.02 0.10 -77. 122. 96. 71.5 

MT----- Helena (ARPT 71)------ 46.60 -111.98 -0.36 -0.07 -11. -246. -236. 71.6 

11 
Appendix B.--Residuals--u.s. reeeat stations and observatories 1 including Alaskan reeeat stations 

--Continued. 

State Station (name) Lat Long Decl Dip Horiz Vert Total Date 

(Abbr~ 0 0 0 0 nT nT nT 

MT---- Helena (GR MDW)------- 46.62 -112.07 -0.74 -0.32 264. -216. -121. 71.6 

MT---- Helena (ARPT 2)------- 46.60 -111.98 -0.50 -0.14 48. -307. -275. 71.6 

MO---- Carrollton------------ 39.37 -93.49 -0.20 -0.06 33. -85. -67. 73.7 

MO---- Rolla (WEST)---------- 37.95 -91.78 -0.64 0.02 31. 124. 127. 73.7 

NE---- Fremont (ARPT-64)----- 41.45 -96.52 o.ss -0.03 -71. -286. -293. 73.7 

NE---- Fremont (ARPT-7 3) ----- 41.45 -96.52 0.62 -0.03 -69. -283. -290. 73.7 

NE---- Halsey (B 73)--------- 41.90 -100.28 0.33 -0.17 163. -49. 10. 73.7 

NE---- Fremont (ARPT)-------- 41.45 -96.52 0.62 -0.03 -69. -283. -290. 7 3. 7 

NV---- Ely (BLM)------------- 39.32 -114.88 0.09 0.08 22. 213. 202. 72.6 

NV---- Las Vegas (M GLF)----- 36.19 -115.18 -0.10 0.39 -296. 191. 30. 72.6 

NV---- Winnemuca (ARPT)------ 40.90 -117.80 -0.22 0.03 -41. -15. -31. 72.6 

NH---- Keene (ARPT)---------- 42.90 -72.26 -0.39 -0.13 170. 100. 148. 73.5 

NH---- Surry----------------- 43.00 -72.32 0.12 0.10 -34. 229. 208. 73.5 

NM---- Deming---------------- 32.25 -107.77 -0.12 -0.04 -2. -77. -68. 72.9 

NM---- Deming (ARPT 72)------ 32.26 -107.72 -0.12 -0.05 1. -85. -73. 72.9 

NM---- Hobbs----------------- 32.68 -103.21 0.74 0.18 -150. 70. -11. 72.7 

NM---- Soccoro (ARPT 72)----- 34.02 -106.90 -0.12 o.os -128. -144. -187. 72.9 

NY---- Syracuse (DRUM)------- 43.02 -76.10 -0.27 0.04 -16. 75. 67. 73.6 

NY---- Syracuse (DRUM B)----- 43.02 -76.11 -0.33 0.03 -9. 80. 73. 73.6 

NC---- Wadesboro------------- 34.94 -80.04 1.40 0.67 -598. 231. -26. 74.4 

NC---- Wilmington (GOLF 1)--- 34.21 -77.87 0.32 0.09 105. 432. 437. 71.3 

NC---- Wilmington (GOLF 2)--- 34.21 -77.87 0.31 0.11 85. 444. 440. 71.3 

NC---- Wilmington (GOLF 2)--- 34.21 -77.87 0.27 0.12 47. 374. 360. 74.4 

ND---- Bowbells-------------- 48.81 -102.25 0.48 -0.08 81. -24. -3. 7 2.6 

ND---- Jamestown------------- 46.91 -98.70 0.72 0.10 -62. 160. 138. 72.6 

ND---- Jamestown (ARPT)------ 46.93 -98.68 0.51 0.11 -55. 230. 207. 72 6 

NO---- Pembina (PARK)-------- 48.97 -97.25 0.11 0.01 -32. -77. -83. 72.6 

OK---- Carmen (PARK)--------- 36.58 -98.45 0.65 -0.05 -38. -202. -200. 73.8 

OK---- Tulsa (LEONARD)------- 35.91 -95.79 0.24 0.01 -so. -87. -100. 73.8 

OR---- Burns (FGNDS)--------- 43.58 -119.02 0.49 0.14 27. 428. 406. 72.6 

OR---- Eugene (RESV)--------- 44.06 -123.29 0.09 -0.09 103. 19. 58. 72.6 

PA---- Indiantown Gap (AF)--- 40.45 -76.55 -0.23 0.01 19. 87. 88. 74.5 

PA---- Indiantown Gap (LAKE)- 40.42 -76.60 -0.26 0.03 -9. 69. 62. 74.5 

RI---- Kingston (CAMPUS)----- 41.48 -71.52 -0.01 0.12 -80. 113. 81. 73.5 

RI---- Kingston (TURF)------- 41.49 -71.55 -0.18 0.29 -162. 397. 323. 73.5 

sc---- Fort Jackson---------- 34.02 -80.92 0.24 0.22 -318. -208. -321. 74.4 

SD---- Belle Fourche 2------- 44.70 -103.87 0.32 -0.11 47. -218. -193. 72.6 

SD---- Huron (CC)------------ 44.40 -98.22 0.23 -0.21 350. 383. 470. 72.6 

TN---- Clarksville 73-------- 36.64 -87.48 0.18 -0.19 -41. -570. -541. 73.6 

TX---- Brownsville (GOLF 2)-- 25.88 -97.50 0.01 0.12 -74. 63. 9. 72.8 

TX---- Austin (DS)----------- 30.21 -98.07 o.os 0.21 -83. 237. 163. 72.8 

TX---- Austin (GOLF)--------- 30.37 -97.69 -0.09 -0.01 -59. -129. -141. 72.8 

TX---- Hereford-------------- 34.86 -102.32 0.57 -0.25 128. -259. -175. 72.7 

TX---- Laredo (NORTH)-------- 27.56 -99.47 0.02 0.01 -53. -60. -80. 7 2.8 

TX---- Laredo (WEST)--------- 27.56 -99.48 0.02 0.01 -53. -67. -85. 72.8 

TX---- Orange (C)------------ 30.06 -93.80 0.08 0.14 -64. 136. 87. 72.9 

TX---- Van Horn (1972)------- 31.05 -104.84 o.oo -0.11 -32. -249. -230. 72.8 

TX---- Pandale--------------- 30.21 -101.37 -0.32 -0.26 164. -169. -60. 72.8 

UT---- Cedar City (ARPT)----- 37.70 -113.09 -0.19 0.16 -117. 100. 38. 73.8 

12 
Appendix B.--Residuals.--u.s. re:2eat stations and observatories 1 including Alaskan re:2eat stations 

--Continued. 

State Station (name) Lat Long Decl Dip Horiz Vert Total Date 

~Abbr~ 0 0 0 0 nT nT nT 

UT---- Salt Lake City-------- 40.78 -111.86 -0.36 -0.10 75. -73. -37. 73.8 

VT---- Burlington (LP) ------- 44.46 -73.16 0.15 -0.28 311. 52. 141. 73.6 

VT---- Burlington (RS)------- 44.47 -73.20 0.13 -0.32 353. 42. 144. 73.6 

WA---- Coulee Dam------------ 48.06 -118.95 -0.01 o.oo 57. 176. 184. 71.5 

WA---- Quillayute------------ 47.94 -124.55 -0.04 -0.04 40. -10. 4. 71.5 

1\lV---- Parkersburg (GOLF)---- 39.28 -81.51 0.16 0.15 -28. 361. 330. 72.4 

WA---- Seattle ( ST EDl\'D) ----- 47.73 -122.26 0.05 0.01 -2. 35. 33. 72.6 

WA---- Seattle (ST THOS)----- 47.73 -122.26 -0.02 0.03 -52. -47. -62. 72.6 

WI---- Tomahawk-------------- 45.47 -89.74 0.49 -0.18 110. -316. -274. 72.6 

WI---- Tomahawk (ARPT)------- 45.47 -89.74 0.01 -0.33 265. -305. -221. 72.6 

WI---- Eau Claire------------ 44.83 -91.53 0.74 -0.20 94. -404. -362. 72.6 

1\'Y---- Sherida~-------------- 44.85 -106.96 -0.24 -0.08 18. -187. -171. 71.6 

WA---- Newport 1-------------- 48.26 -117.12 0.12 0.01 1. 33. 32. 74.5 

co---- Boulder -------------- 40.14 -105.24 0.17 -0.11 20. -224. -200. 74.5 

VA---- Fredericksburg1

------- 38.20 -77.37 -0.19 0.04 47. 222. 224. 74.5 

CA---- Castle Rock 1

---------- 37.24 -122.13 0.04 0.17 -123. 83. 15. 74.5 

TX---- Dallas 1

--------------- 32.99 -96.75 0.41 -0.13 17. -220. -188. 74.5 

AZ---- Tucson1

--------------- 32.25 -110.83 -0.12 0.20 -109. 166. 87. 74.5 

AK---- Anchorage (NBS)------- 61.24 -149.87 0.63 0.18 -21. 565. ' 537. 75.4 

AK---- Barter Is (IGY)------- 70.13 -143.65 0.40 0.07 -85. -77. -89. 75.6 

AK---- Bethel (AIRPORT)------ 60.78 -161.83 0.40 0.07 9. 241. 231. 75.7 

AK---- Chitina--------------- 61.52 -144.44 0.66 -0.13 102. -116. -85. 75.5 

AK---- Cordova 3 (1975) ------ 60.55 -145. 76 -0.07 -0.08 103. 82. 108. 75.5 

AK---- Fort Yukon (IGY)------ 66.56 -145.26 -0.03 0.10 -112. -56. -78. 75.6 

AK---- Homer 1 (AIRPORT)----- 59.64 -151.49 -0.81 -0.07 73. 2. 24. 75.4 

AK---- Hughes (1975)--------- 66.05 -154.26 0.91 0.15 -198. -209. -249. 75.7 

AK---- Kenai (APT) 1975------ 60.56 -151.26 0.32 0.19 -48. 480. 445. 75.4 

AK---- Kodiak (1975)--------- 57.80 -152.37 0.26 -0.02 47. 80. 91. 75.5 

AK---- Kotzebue (IGY)-------- 66.88 -162.64 0.40 -0.09 62. -119. -101. 75.6 

AK---- Kotzebue ( 19 7 5) ------- 66.88 -162.64 0.33 -0.03 8. -88. -84. 75.6 

AK---- Nome (APT) Aux A (58)- 64.53 -165.37 0.19 -0.02 -20. -129. -130. 75.6 

AK---- Northway (IGY) 2------ 63.02 -141.80 0.21 0.17 -131. 163. 128. 75.5 

AK---- Platinum-------------- 59.02 -161.82 -0.67 0.32 -301. 47. -56. 75.7 

AK---- Pt Hope (CEMETERY)---- 68.35 -166.78 o. 71 -0.12 114. -40. -14. 75.6 

Ak---- Prudhoe Bay (1975) ---- 70.29 -148.70 0.46 0.05 -73. -123. -134. 75.6 

AK---- Ruby 3 (1975)--------- 64.73 -155.46 0.19 -0.06 46. -69. -55. 75.6 

AK---- Seward---------------- 60.13 -149.42 0.60 -0.03 68. 115. 130. 75.5 

AK---- Shungnak-------------- 66.89 -157.03 0.31 -0.05 63. 38. 51. 75.6 

AK---- Unalakleet (1975) ----- 63.89 -160.80 0.57 0.04 -25. 45. 36. 75.7 

AK---- Unalaska-------------- 53.86 -166.55 1.22 -0.28 152. -266. -179. 75.7 

AK---- Yakutai 5 (1975)------ 59.51 -139.66 -0.21 0.16 -162. -1. -43. 75.5 

AK---- Barrow --------------- 71.30 -156.75 0.46 -0.07 49. -116. -106. 74.5 

AK---- 1 Collete 64.86 -147.84 0.26 0.06 -67. -25. -40. 74.5 -------------- AK---- Sitka ---------------- 57.06 -135.33 0.13 -0.08 63. -67. -47. 74.5 

Observatory. 

13 
Declination for band 

1 in conterminous 

48 States 

-1. 28334e+001 

5.01082e-001 

-7. 83442e-OO 1 

-1.27714e-002 

4. 01399e-004 

2.24954e-002 

3.13086e-004 7 

4.48060e-004 8 

-1. 10156e-003 9 

9. 448 7 5e-004 10 

9.11331e-006 11 

5.93444e-005 12 

-3. 52190e-006 13 

7. 38989e-005 14 

-3. 28303e-004 15 

6.01171e-007 16 

-5. 53779e-006 17 

-1.60637e-006 18 

-2. 9465 7e-006 19 

4. 97808e-006 20 

-7.12612e-006 21 

-5.90044e-008 22 

-3. 61589e-007 23 

1.30831e-007 24 

-5. 39791e-008 25 

-3.82329e-008 26 

-4. 19099e-00 7 27 

2. 71842e-006 28 

-1. 59998e-010 29 

2.66724e-008 30 

-1. 07483e-008 31 

-1.20473e-008 32 

3. 34444e-008 33 

3. 90318e-008 34 

-3.19948e-008 35 

3.55637e-008 36 

Appendix C.--coefficients of chart models 

[The coefficients can be related to the function as follows: The 

coefficients numbered 1, 2, 3, 4, 5, 6, ••• 35, 36 are equivalent to 

the coefficients a 00 , a10, a20• a21' a22••••a77, of the function] 

Declination for band Declination for band Declination for band Declination for band 

2 in conterminous 3 in conterminous 4 in conterminous 5 in conterminous 

48 States 48 States 48 States 48 States 

-2.6 7351e+OOO 6. 75344e+OOO 1. 30355e+001 1. 62869e+001 

2. 93044e-OO 1 -2.61824e-002 -2.64830e-001 -4.1734 7e-OO 1 

-8. 34178e-001 -6.07717e-001 -4. 03658e-001 -1. 79067e-001 

-1.93867e-002 -1.48153e-002 -9.50477e-004 6. 25598e-003 

2. 36374e-002 3.12457e-002 1. 73702e-002 1.14608e-OOZ 

1.12795e-002 6 -1.00242e-002 6 -1. 41128e-002 6 -7. 7727le-003 6 

1.57874e-003 7 1. 84189e-003 7 4. 06045e-004 7 1. 43361e-004 7 

-2. 94205e-004 8 -1.49579e-003 8 -6.43100e-004 8 2. 79125e-004 8 

-1. 02440e-003 9 1. 43483e-003 9 4. 28903e-004 9 1. 5 7742e-004 9 

-2. 44400e-003 10 -9.51459e-004 10 2. 70990e-004 10 1.65545e-004 10 

1. 65647e-004 11 1. 61507e-004 11 5. 78007e-005 11 4. 11723e-006 11 

1. 50505e-005 12 -1.15636e-004 12 1.63057e-005 12 -7. 78303e-005 12 

1. 24418e-005 13 7. 82886e-005 13 3. 03403e-005 13 7.57472e-005 13 

-1.10751e-004 14 2. 73149e-005 14 5. 68502e-006 14 -7.25254e-005 14 

-3. 42778e-004 15 -4. 35186e-005 15 1. 40600e-005 15 -5. 68903e-005 15 

-1.31804e-005 16 -1.72357e-005 16 -4.28104e-006 16 -2. 37039e-006 16 

-7. 94 7 59e-006 17 1. 51265e-005 17 3. 08059e-006 17 1. 50295e-006 17 

-1.91323e-005 18 -1.97283e-005 18 -2.19284e-006 18 8.47179e-006 18 

1. 87905e-005 19 -3. 45291e-006 19 3. 48935e-006 19 -2. 91265e-005 19 

4. 95508e-005 20 -1.24430e-005 20 2.15235e-006 20 1.40922e-005 20 

5. 29946e-005 21 1. 21007e-005 21 -1. 37227e-005 21 1. 76083e-006 21 

-7 .03108e-007 22 -4.9897 5e-007 22 -1.43236e-007 22 -2. 33909e-008 22 

2. 07349e-007 23 5. 00559e-007 23 -3. 37714e-008 23 2.62577e-007 23 

6. 24651e-008 24 -4.41287e-007 24 -1. 65453e-007 24 -4.61616e-007 24 

-3. 95413e-007 25 5. 95931e-007 25 -1. 64965e-008 25 7. 1 0883e-007 25 

-8.15560e-008 26 -1.80810e-007 26 -2.04933e-007 26 1. 69253e-007 26 

1.19152e-006 27 -1. 25743e-006 27 9. 80213e-008 27 -1. 26358e-006 27 

2.62015e-006 28 4.17432e-007 28 2. 92552e-007 28 1. 4 7 596e-006 28 

4. 77462e-008 29 4. 68736e-008 29 9. 88~92e-009 29 6.27482e-009 29 

1.87578e-008 30 -5.95585e-008 30 -9 .18516e-009 30 -8.55351e-009 30 

4. 05456e-008 31 7. 54625e-008 31 5. 95536e-009 31 -4. 70189e-008 31 

-1.07154e-008 32 -2. 59804e-008 32 1.05229e-008 32 1.34212e-007 32 

5. 66433e-008 33 7.195 75e-008 33 1. 3 7968e-008 33 -2. 76226e-008 33 

-1.53129e-007 34 9.23312e-008 34 -6. 92023e-008 34 -4.80626e-008 34 

-4. 16239e-007 35 -4. 68828e-009 35 -1. 36467e-008 35 2. 3 7465e-008 35 

-2.64805e-007 36 -7. 84304e-008 36 1. 52980e-007 36 -8.59178e-009 36 

Horizontal intensity for Vertical intensity for Secular change in 

conterminous 48 States conterminous 48 States horizontal intensity 

for 48 States 

1.11283e+004 -4.92413e-006 21 2. 22299e+004 -9.27872e-006 21 3.45744e+001 

5. 93553e+002 -2. 07456e-005 22 -8. 05063e+002 4. 24327e-006 22 -3. 70315e+OOO 

-9. 76034e+001 5. 6906 4e-006 23 8.25874e+001 -2.58297e-006 23 2. 63540e+OOO 

-7.37877e+OOO -5. 69877e-007 24 -1. 65495e+001 -8. 0 1126e-006 24 -1.61374e-001 

-1.39807e-001 1.41786e-006 25 5.82352e+OOO 1. 656 7 Je-006 25 -2.14846e-002 

1. 76988e+OOO 6 -1. 77985e-006 26 -7.58918e+OOO 6 -3. 036 78e-0'06 26 4.01055e-002 6 

-1.23084e-001 7 -3.64791e-007 27 1.65418e-001 7 1.24441e-006 27 7. 56505e-003 7 

1.06707e-001 8 -4. 97382e-007 28 -1. 30201e-001 8 -3. 95024e-007 28 -5.45952e-003 8 

-2.53787e-001 9 -1. 86331e-007 29 3.81803e-002 9 3. 37905e-007 29 2. 64150e-003 9 

6. 94785e-002 10 -6. 84156e-008 30 -4. 28637e-002 10 -6. 94873e-007 30 -1.10277e-003 10 

1.01022e-002 11 -3.28319e-008 31 3.09667e-003 11 -1.32518e-007 31 9. 34116e-004 11 

-4. 45213e-003 12 1. 00894e-007 32 4. 5 7084e-004 12 -2. 68581e-007 32 9.15822e-005 12 

2.05698e-003 13 7.58462e-009 33 1.13402e-002 13 3.81435e-008 33 -4. 94533e-005 13 

8. 49875e-004 14 -2.2 7681e-009 34 -4. 59439e-003 14 4.44719e-008 34 5.47427e-005 14 

4. 39136e-004 15 -3.43554e-008 35 1. 79758e-003 15 1.62086e-008 35 -2. 62497e-005 15 

-9. 48324e-009 36 s. 55452e-009 36 

3. 38103e-004 16 -1. 74924e-004 16 -6.85746e-006 16 

-7. 43830e-005 17 5.25474e-004 17 -1. 38716e-007 17 

9.43317e-005 18 3. 66931e-005 18 -4.11077e-006 18 

-9.52152e-005 19 2.66568e-005 19 1. 84179e-006 19 

1.18625e-004 20 -s. aoo20e-oos 20 -6. 31355e-007 20 

1. 70413e-007 21 

-2.05289e-006 22 

-1. 61247e-008 23 

-1.91784e-007 24 

-8. 08162e-008 25 

4. 97069e-008 26 

-2.2 7589e-008 27 

3.80636e-009 28 

14 

Secular change in 

conterminous 

48 States 

-5. 91190e+OOO 

-1.68142e-001 

-6. 48094e-002 

5. 93866e-003 

-2. 44053e-002 

5.85988e-003 6 

-3. 50743e-004 7 

3. 53160e-004 8 

-6. 38998e-005 9 

2. 92968e-004 10 

3.15289e-005 11 

5.54197e-005 12 

-9.22212e-006 13 

1.83674e-OOS 14 

3. 60506e-006 15 

9.04572e-007 16 

3. 37064e-007 17 

1. 8804 Se-00 7 18 

-3. 41158e-007 19 

3. 90881e-008 20 

-1. 23375e-007 21 

-9.4927le-008 22 

-1.11951e-007 23 

1. 23254e-008 24 

-2. 28627e-008 25 

-4.11474e-009 26 

-4. 37217e-009 27 

-2.49154e-009 28 

Secular change in 

vertical intensity 

for 48 States 

-5. 37212e+001 1 

-4.10167e+OOO 2 

-1. 70578e+OOO 3 

2. 71050e-001 4 

-1. 65244e-001 5 

-7.91053e-002 6 

5. 79294e-003 7 

2.38760e-003 8 

-3. 30138e-004 9 

8.04257e-004 10 

-1. 13355e-003 11 

5. 58 794e-005 12 

-1. 78677e-005 13 

... 1.95663e-005 14 

1.10482e-004 15 

-6 .10629e-006 16 

-4. 91566e-006 17 

-2. 97886e-006 18 

-6. 65628e-007 19 

1.59898e-007 20 

-8. 00258e-008 21 

2. 05089e-00.6 22 

2. 94269e-007 23 

3.37098e-007 24 

4. 86363e-008 25 

-1. 26056e-007 26 

5. 20045e-008 27 

-3.8345le-008 28 
Appendix C.--coefficients of chart models--continued 

Declination for Horizontal inten- Vertical intensity Secular change in Secular change in Secular change in 

Alaska sity for Alaska jor Alaska declination for horizontal inten- vertical intenAlaska sit~ for Alaska sity f.or Al.aska 

2.15098e+001 1 1.28701e+004 1 2.0657le+004 1 1. 95174e-001 1 1. 21089e+001 1 -8. 40721e+OOO 1 

-3.12571e-001 2 5.18878e+002 2 -6. 05428e+002 2 -5.30394e-002 2 -1.03493e+OOO 2 -8. 68283e-OO 1 2 

4.91087e-001 3 -1.00820e+002 3 1.97897e+002 3 -6. 93826e-002 3 2. 69529e-001 3 3. 36583e-001 3 

3.23674e-003 4 -9.02027e+OOO 4 -9. 99413e+OOO 4 -9. 20386e-004 4 1.09158e-003 4 1.22695e-002 4 

-1.86390e-002 5 2.58613e+OOO 5 8.84446e+OOO 5 -1. 45384e-003 5 7. 4 7848e-003 5 -3.19064e-002 5 

-5. 69661e-003 -1. 40507e+OOO 6 2. 89759e+OOO 6 -1.03906e-003 6 9.37768e-003 6 -4.80588e-003 6 

2. 77264e-005 7 -6.59361e-002 7 -2.26663e-002 7 -1.32668e-006 7 1.12332e-004 7 1. 02101e-003 7 

4. 11507e-004 8 2. 72348e-001 8 -2.16847e-001 8 1.00093e-004 8 -1.53755e-003 8 -9.26915e-004 8 

-3.34078e-004 9 6.11470e-002 9 3.1065 7e-002 9 -4. 85534e-005 9 2.18876e-004 9 -8. 09038e-004 9 

-1. 72609e-005 10 -9.0 14lle-003 10 -3. 77748e-002 10 -7.96214e-007 10 3.61790e-005 10 8. 37542e-006 10 

1.38057e-005 11 2.41091e-003 11 -2.56118e-003 11 2. 88554e-005 11 -1. 25999e-005 11 1. 56455e-004 11 

-4. 08427e-006 12 -6. 30494e-003 12 -9.13153e-003 12 4.68273e-006 12 -6 .11094e-005 12 1.1179 Se-004 12 

1.43227e-005 .13 4. 71303e-003 13 -6.19806e-003 13 9. 25196e-007 13 -2. 82389e-005 13 -4. 74751e-006 13 

-3. 78117e-008 14 -4.12616e-004 14 -6.4 7016e-004 14 2. 22493e-007 14 9.39469e-006 14 -9.60527e-006 14 

3.43098e-007 15 -1.14520e-004 15 -6.21374e-004 15 1. 5620le-007 15 -3. 91379e-006 15 3. 8 7091e-006 15 

-1. 45688e-006 16 -1.5 7527e-005 16 1. 2 7664e-003 16 1. 0606 Oe-00'1 16 1.63643e-006 16 -1.91582e-006 16 

-1.41208e-006 17 -3.36178e-004 17 1.22739e-004 17 -1.23968e-007 17 1. 49433e-006 17 1.67819e-006 17 

8. 36353e-007 18 -9. 66833e-005 18 1. 94955e-004 18 1.27469e-007 18 -3.68627e-007 18 4.45756e-007 18 

-2.13940e-007 19 -7 .09362e-005 19 5.85795e-005 19 -1. 50581e-008 19 1. 38704e-007 19 -4. 37977e-007 19 

1. 92664e-007 20 3. 59370e-006 20 3. 88 7 50e-006 20 -1.11625e-008 20 -7 .57077e-009 20 1. 84588e-007 20 

-4. 30511e-008 21 3.09613e-006 21 -3.02166e-006 21 6. 11890e-009 21 -7. 56994e-009 21 2.10814e-008 21 

-4. 39980e-008 22 7. 94337e-006 22 8. 3 7796e-006 22 -6.18670e-008 22 -8. 26998e-009 22 -3.34610e-007 22 

1.99973e-008 23 9. 40849e-006 23 3. 91646e-006 23 1. 76829e-009 23 9. 34528e-008 23 -9. 34949e-008 23 

-4. 5 7007e-009 24 -4. 09482e-006 24 5. 44917e-006 24 -4. 22369e-009 24 3.68985e-008 24 4.87487e-009 24 

2.50965e-009 25 -1.35836e-007 25 1.43020e-006 25 -9. 96162e-011 25 -8. 15906e-009 25 -1. 72291e-008 25 

-2. 70142e-009 26 -5. 05727e-007 26 1. 30237e-006 26 1.58122e-013 26 3.22362e-009 26 -4. 20822e-009 26 

1. 40864e-009 27 -2. 22449e-007 27 -2.34036e-007 27 -3. 36216e-010 27 -1.07443e-009 27 4.67631e-009 27 

-2. 22711e-010 28 1. 02968e-007 28 1. 68652e-007 28 7. 60982e-Oll 28 7. 79046e-010 28 -4.13954e-010 28 

9.37746e-010 29 -2.69126e-007 29 -2.24851e-006 29 1. 20184e-009 30 2.12069e-007 30 1. 73023e-008 30 

-1.83249e-010 31 1.68482e-007 31 -2. 78735e-007 31 1. 0 3445e-009 32 5. 70517e-008 32 -2. 49108e-008 32 -7 .40522e-010 33 -3.31915e-009 33 -8. 866 30e-008 33 9.24793e-Oll 34 3. 007 40e-008 34 -3.19313e-009 34 -2.09843e-Oll 35 -5.55377e-009 35 6.01991e-009 35 6.52480e-012 36 -7.13698e-010 36 -3. 49593e-010 36 

15 *U.S. GOVERNMENT PRINTING OFFICE: 1979-6n-026/48