U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2015–1125

The Boulder Magnetic Observatory

The Boulder Magnetic Observatory

By Jeffrey J. Love, Carol A. Finn, Kolby L. Pedrie, and Cletus C. Blum

Open-File Report 2015–1125

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2015

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

resources, natural hazards, and the environment—visit http://www.usgs.gov or call 1–888–ASK–USGS.

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod/.

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Love, J.J., Finn, C.A., Pedrie, K.L., and Blum, C.C., 2015, The Boulder magnetic observatory: U.S. Geological Survey 

Open-File Report 2015–1125, 8 p., http://dx.doi.org/10.3133/ofr20151125.

ISSN 2331-1258 (online)
iii

Contents

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

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

Location...........................................................................................................................................................1

Operational History........................................................................................................................................1

Facilities...........................................................................................................................................................2

Data Types.......................................................................................................................................................3

Partners...........................................................................................................................................................3

Natural Signals...............................................................................................................................................3

Derived Products ...........................................................................................................................................3

Workshop ........................................................................................................................................................4

Induction Hazards: Future Developments .................................................................................................4

Acknowledgments.........................................................................................................................................5

References Cited............................................................................................................................................6

Figures

1. Aerial view of the USGS Boulder magnetic observatory site ...............................................2

2–4. Graphs showing:

 2. Boulder geomagnetic data for years 1967–2013 ..............................................................4

 3. Quiet time Boulder geomagnetic variation for November 17–22, 2008 ........................5

 4. Magnetic storm Boulder geomagnetic variation for October 29–31, 2003 ..................6

The Boulder Magnetic Observatory

Jeffrey J. Love, Carol A. Finn, Kolby L. Pedrie, Cletus C. Blum

Abstract

The Boulder magnetic observatory has, since 1963, been 

operated by the Geomagnetism Program of the U.S. Geological 

Survey in accordance with Bureau and national priorities. Data 

from the observatory are used for a wide variety of scientific 

purposes, both pure and applied. The observatory also supports 

developmental projects within the Geomagnetism Program and 

collaborative projects with allied geophysical agencies.

Introduction

The Boulder observatory is one of 14 magnetic observatories operated across the United States and Territories by the 

Geomagnetism Program of the U.S. Geological Survey (USGS) 

(Love and others, 2008). Along with the other observatories 

in the Program’s network, the Boulder observatory is operated 

in accordance with strategic goals for geophysical observation 

established for the USGS Hazards Mission Area (Holmes and 

others, 2013), in support of the interagency U.S. National Space 

Weather Program (NSWP, 2010), and as a service to the scientific community (Love, 2008; Love and Finn, 2011).

Magnetometer data from the USGS observatory network 

have high time resolution, accuracy, and continuity. These 

properties mean that the data are useful for a wide variety of 

research and operational applications (Love, 2008), including 

(1) analysis and mapping of the main field generated in the 

Earth’s deep interior, (2) analysis and real-time monitoring 

of magnetic variation generated by dynamic conditions in the 

Earth’s space weather environment, (3) assessment and mitigation of magnetic storm interference and hazards for the activities and infrastructure of our technologically based society 

(Love and Finn, 2011).

Because the Boulder observatory is relatively close to 

the USGS Geomagnetism Program headquarters in Golden, 

Colorado, the site is used by Geomagnetism Program engineers and technical staff to develop, calibrate, and test new 

sensors, acquisition systems, and operational procedures (for 

example, Worthington and others, 2009; White and others, 

2014). The observatory supports allied geophysical measurement systems, and it is used for training Program staff and 

visiting technicians. In all of these respects, then, the Boulder 

observatory plays a critical role in supporting the entire mission of the USGS Geomagnetism Program.

Location

The Boulder observatory is located on what is known as 

the Table Mountain Field Site, a flat-top butte composed 

of young Quaternary alluvium north of the city of 

Boulder, Colorado, just east of the Rocky Mountains 

(40.1375° N, 105.2372° W), 1,682 meters (m) above sea level 

(Green, 1992). The land immediately surrounding the observatory is rocky and interspersed with grass and cactus. The 

climate is semiarid with an average annual temperature of about 

11 degrees Celsius. The average annual precipitation is 47 centimeters, often coming in the form of summer thunderstorms and 

winter snowfall. Although the USGS owns the observatory infrastructure and is responsible for observatory operations within a 

1,000-ft (305-m) radius circle centered on the electronics building (discussed below), the land itself is owned by the National 

Telecommunications and Information Administration (NTIA) of 

the United States Department of Commerce (DOC).

Operational History

The history of the Boulder observatory can be traced 

back to September 1960, when the National Bureau of 

Standards (NBS) of the DOC constructed a nonmagnetic 

building for data acquisition on its main campus site in the city 

of Boulder. Magnetic measurement using photographic analog 

systems commenced in December 1960. At that time, the 

Coast and Geodetic Survey (C&GS) of the DOC was responsible for the operation of several magnetic observatories in the 

United States. Under terms of an April 15, 1963 memorandum 

of understanding, magnetic measurement operations were 

transferred from NBS (1963) to C&GS. The first reported 

hourly mean data from the Boulder observatory are in the 

archives of the World Data Center in Kyoto, Japan. These data 

were derived from analog magnetograms for April 1963, and, 

thus, operations at the Boulder observatory commenced in 

time to contribute to the International Year of the Quiet Sun of 

1964. The first published geomagnetic measurements made on 

the present site of the Boulder observatory, at Table Mountain, 

were made on July 16, 1964.

On July 13, 1965, the C&GS was consolidated into 

the Environmental Science Services Administration of the 

DOC, which, subsequently, became the National Oceanic and 

Atmospheric Administration (NOAA) on October 3, 1970. A 

memorandum of understanding effective on May 27, 1973, 
2 The Boulder Magnetic Observatory

transferred ownership and operational responsibility of most 

U.S. magnetic observatories, including the observatory at 

Boulder, from NOAA (DOC) to USGS of the Department of 

the Interior (DOI).

The first published 1-minute data values from Boulder 

are for March 1978. These were made using digital acquisition systems. The 1-minute digital data values represent a 

substantial improvement in temporal resolution over 1-hour 

analog data values. Boulder observatory data for the year 

1991 contributed to the first joint certification and publication 

of 1-minute data by the international consortium of magnetic 

observatory institutes known as INTERMAGNET (Love and 

Chulliat, 2013). Since June 13, 2011, Boulder 1-second data 

have been reported to INTERMAGNET. Since 1991, dataacquisition operations at Boulder have been maintained with 

approximately 97 percent continuity.

Facilities

The Boulder observatory consists of several small buildings; these serve a variety of functions, and many of them are 

made of nonmagnetic material; see figure 1. For magnetic 

measurement operations, the variations building houses a 

fluxgate magnetometer and a backup fluxgate magnetometer, 

each maintained at a stable operating temperature. Near this, an 

Overhauser proton-precession magnetometer is housed in a small 

hut. The electronics building contains data display computers, 

network connections, and office space. For review of observatory instrumentation see Rasson (2007).

The Boulder absolutes building houses a specially 

designed theodolite made of nonmagnetic material and having a 

small magnetometer attached to its telescope. This instrument is 

commonly referred to as a declination-inclination magnetometer 

(DIM). It is situated on a stable pier that serves as a reference 

point for the entire observatory. The observatory site has several 

azimuthal reference markers, also on stable piers, and whose 

orientation relative to the theodolite pier have been carefully 

measured using geodetic methods.

A coil system, used for testing and calibrating acquisition 

systems, is housed in its own dedicated building on the Boulder 

site (White and others, 2008); a separate building houses modern coil-control electronic systems and power supplies. Two 

cubical buildings are used for testing new sensor and acquisition 

systems. A storage building is located about 200 m from the 

operational and testing buildings.

Figure 1. Aerial view of the USGS Boulder magnetic observatory site. (Conc., concrete; Bldg., building)
Derived Products 3

Data Types

Continuous second-to-second change, or “variation,” in the geomagnetic field is measured at the Boulder 

observatory with a fluxgate magnetometer (for example, 

Primdal, 1979; Narod and Bennest, 1990). These data 

are sufficient for many applications, such as monitoring geomagnetic space weather phenomena evolving over 

timescales of a few hours or less. Variation data are available to the user community in real-time as a preliminary 

data product from both the USGS Geomagnetism Program 

and INTERMAGNET.

For many applications, however, magnetic variation 

needs to be defined relative to an accurate baseline. Two different sensors provide accurate auxiliary data. An Overhauser 

magnetometer (for example, Hrvoic and Hollyer, 2005) 

provides continuous absolute magnetic field intensity data, 

and the DIM instrument is used by an observatory worker 

twice a week or so to make visual measurements of absolute 

field direction. These auxiliary data are combined with the 

variometer data through computer-based processing to produce calibrated data (for example, Jankowski and Sucksdorff, 

1996). Promptly processed data, known as “quasi-definitive,” 

are available to the user community within a few months of 

preliminary data acquisition.

Final “definitive” data, an accurate representation of 

the Earth’s magnetic field at the Boulder site, are reported 

to INTERMAGNET and made available to the user 

community on an annual schedule. Long-term archives of 

definitive observatory data are maintained in the World 

Data System.

Partners

The USGS Geomagnetism Program collaborates with 

the University of Washington by supporting the operation of 

a very low frequency (VLF) (3–30 kilohertz) band antenna 

on the Boulder observatory site for the World Wide Lightning 

Location Network (WWLLN; Lay and others 2004). The 

WWLLN is a collaboration between universities and government labs from around the world for collecting lightninggenerated VLF electric field waveform signals. These are used 

to estimate the location and time of lightning strikes around 

the world, in real time.

Natural Signals

A long-term view of Boulder observatory magnetic field 

data is provided in figure 2, for years 1967–2013. Here, annual 

mean values (green) of horizontal intensity (H), declination 

(D), and the vertical component (Z) of the magnetic field 

exhibit a slow secular drift. This variation is global in scale 

and driven by fluid convection in the Earth’s core. Note that 

in the 46 years of time represented in figure 2, declination has 

changed by about 4 degrees at Boulder.

Relatively more rapid variation of the Boulder geomagnetic field is seen in figure 2 as the variance of hourly 

mean values (black) about the slower secular variation. This 

variation occurs in two distinctively different ways: quiet 

time variation and magnetic-storm variation. Periodic variation in the geomagnetic field is easily seen in observatory data 

when magnetic conditions are relatively quiet (for example, 

Owolabi and others, 2014). Electric currents in the Earth’s 

electrically conducting day-side ionosphere are generated by 

thermospheric winds that are, themselves, driven by day-night 

differential solar heating. In figure 3, we show an example 

of solar-quiet variation recorded in Boulder 1-minute data, 

November 17–22, 2008; note the prominent quasi-diurnal 

signal in each of the magnetic field components.

Magnetic storms are caused by the dynamic interaction 

of the solar wind with the Earth’s magnetosphere. In observatory data, storms are seen as a distinctive transient variation. 

In figure 4 we show Boulder data recording the Halloween 

storm of October 29–31, 2003 (for example, Gopalswamy 

and others, 2005). This storm caused operational stress in the 

Swedish (Pulkkinen and others, 2005) and Scottish power 

grids (Thomson and others, 2005). The storm commenced 

with the arrival at Earth of a coronal mass ejection, which 

abruptly compressed the magnetopause and generated the 

positive impulse seen in Boulder Z at 06:13 UT on October 29. 

Complex geomagnetic variation was driven by the arrival of 

additional coronal mass ejections, solar wind variability, and 

vigorous magnetospheric convection. What followed was 

storm main-phase intensification of magnetic activity that 

lasted for more than 2 days.

Derived Products

Data from the Boulder observatory are used by NOAA’s 

Space Weather Prediction Center (SWPC) for real-time assessment of mid-continental geomagnetic conditions within the 

United States (for example, Balch and others, 2004). Boulder 

observatory data contribute to the U.S. Air Force calculation 

of an American version of the Kp index (Gehred and others, 

1995), a traditional measure of global geomagnetic activity 

that has historically been used for space weather assessment 

(for example, Mayaud, 1980). The Kyoto World Data Center 

in Japan uses Boulder data for the calculation of the symmetric (SYM) and asymmetric (ASY) indices (Iyemori and Rao, 

1996). These indices represent, respectively, the symmetric 

and asymmetric parts of the magnetospheric equatorial ring 

current, both of which are fundamental quantities used for 

analysis of magnetic storm dynamics. Boulder data are used 

in the derivation of the International Geomagnetic Reference 

Field (IGRF), a spherical harmonic model of the main part 

of the Earth’s magnetic field. Widely used for scientific 

research, navigation, and near-surface magnetic surveys, the 
4 The Boulder Magnetic Observatory

IGRF is constructed using a combination of data from satellites, ground surveys, and magnetic observatories—including 

data from the Boulder observatory (for example, Finlay and 

others, 2010).

Workshop

The 13th biennial International Association of 

Geomagnetism and Aeronomy (IAGA) Workshop on 

Geomagnetic Observatory Instruments, Data Acquisition and 

Processing was hosted by the USGS Geomagnetism Program, 

June 9–18, 2008. This was the first time this important workshop was held in the United States. More than 100 participants, 

representing many different institutions came from 36 countries 

and 6 continents. In preparation for the workshop, several new 

absolutes piers were installed at the Boulder observatory to 

facilitate simultaneous measurement of the absolute direction 

and intensity of the geomagnetic field (Berarducci and Woods, 

2009; White, 2009). Results of the measurement session and the 

presentations given during the scientific session are presented in 

the Workshop’s proceedings (Love, 2009).

Induction Hazards: Future Developments

The Boulder observatory has recently become a focal 

point for the USGS Geomagnetism Program and its support of 

a multiagency project for studying, monitoring, and evaluating magnetic storm hazards (Love and others, 2014; NSTC, 

2015). Of concern is the storm-time induction of geoelectric 

Figure 2. Boulder geomagnetic data for years 1967–2013, hourly values (black) and annual mean variation 

(green): A, horizontal intensity (H); B, declination (D); and C, vertical component (Z). (deg, degrees; nT, nanoTesla)

22.0

21.5

21.0

20.5

H x 103 (nT) Z x 103 (nT)

14

13

12

11

10

9

52.0

51.5

51.0

50.5

50.0

49.5

49.0

48.5

D (deg)

1970 1980 1990

Year

2000 2010

A

B

C
Acknowledgments 5

fields in the Earth’s electrically conducting lithosphere. 

Corresponding voltage differentials can find their way into 

electric-power grids through ground connections, driving 

uncontrolled electric currents that interfere with grid operation, sometimes causing blackouts (for example, Boteler and 

others, 1998).

One part of this induction-hazard project is focused 

on real-time mapping of storm-time magnetic disturbance 

across North America using data from the USGS and 

Canadian observatory networks (Pulkkinen and others, 

2003; Rigler and others, 2014). For this, magnetic data from 

the Boulder observatory, with its location in the continental interior, will play an important role in constructing such 

maps and validating their accuracy. Another part of the 

project is focused on estimating the storm-time induction 

of geoelectric fields, and, as a check of such estimates, the 

geoelectric field will be directly monitored at the Boulder 

observatory site.

Other possible operational opportunities for the Boulder 

observatory include testing electromagnetic crustal exploration 

systems, and development of a joint U.S.–Canadian calibration 

facility. In the coming years, the Boulder magnetic observatory 

will certainly remain an important site for operations and developments within the USGS Geomagnetism Program.

Acknowledgments

We thank Connor Fisher, Teri Losano, Jill McCarthy, 

Joy Monson, Melanie Parker, E.J. Rigler, J.L. Slate, T.C. White, 

and E.W. Worthington for reading a draft manuscript.

Figure 3. Quiet time Boulder geomagnetic variation for November 17–22, 2008, minute values (black) 

relative to absolute baseline (green): A, horizontal intensity (H); B, declination (D); and C, vertical component 

(Z). (deg, degrees; nT, nanoTesla)

40

20

0

–20

H variation (nT) Z variation (nT)

–40

0.15

0.10

0.05

0.00

–0.05

–0.10

–0.15

40

20

0

–20

–40

D variation (deg)

1 2 3

Days after 00.00 November 17, 2008 (UT)

4 5 6

A

B

C
6 The Boulder Magnetic Observatory

References Cited

Balch, Christopher, Murtagh, Bill, Zezula, David, Combs, 

Larry, Nelson, Gayle, Tegnell, Ken, Crown, Misty, McGehan, 

Barbara,, 2004, Service assessment, intense space weather 

storms October 19–November 07, 2003: United States 

Department of Commerce, National Oceanic and Atmospheric Administration, Silver Spring, Md., 49 p.

Berarducci, Alan and Woods, Andy, 2009, Absolute measurement session, in Proceedings of the XIIIth IAGA Workshop 

on geomagnetic observatory instruments, data acquisition, 

and processing (Love, J.J. ed.): U.S. Geological Survey 

Open-File Report 2009–1226, p. 1–8.

Boteler, D.H., Pirjola, R.J., and Nevanlinna, H., 1998, The effects 

of geomagnetic disturbances on electrical systems at the 

Earth’s surface: Advances in Space Research, v. 22, p. 17–27.

Finlay, C.C., and others, 2010, International geomagnetic reference field—The eleventh generation: Geophysical Journal 

International, v. 183, no. 3, p. 1216–1230.

Gehred, P.A., Cliffswallow, W. and Schroeder III, J.D., 1995, 

A comparison of USAF Ap and Kp indices to Göttingen 

indices: National Oceanic and Atmospheric Administration, 

Silver Spring, Md., Technical Memorandum Environmental 

Research Laboratories SEL-88, 26 p.

Gopalswamy, N., Barbieri, L., Cliver, E.W., Lu, G., Plunkett, 

S.P. and Skoug, R.M., 2005, Introduction to violent SunEarth connection events of October–November 2003: 

Journal of Geophysical Research, vol. 110, A09S00, 

doi:10.1029/2005JA011268.

Green, G.N., 1992, The digital geologic map of Colorado 

in ARC/INFO Format: U.S. Geological Survey Open-File 

Report 92–0507, 9 p.

Figure 4. Magnetic storm Boulder geomagnetic variation for October 29–31, 2003, minute values 

(black) relative to absolute baseline (green): A, horizontal intensity (H); B, declination (D); and C, vertical 

component (Z). (deg, degrees; nT, nanoTesla)

400

200

0

–200

H variation (nT) Z variation (nT)

–400

0.8

0.4

0.0

–0.4

–0.8

400

200

0

–200

–400

D variation (deg)

6 12 18 24 30 36 42

Hours after 00:00 October 29, 2003 (UT)

48 54 60 66 72

A

B

C
References Cited 7

Holmes, R.R., Jones, L.M., Eidenshink, J.C., Godt, J.W., Kirby, 

S.H., Love, J.J., Neal, C.A., Plant, N.G., Plunkett, M.L., 

Weaver, C.S., Wein, Anne and Perry, S.C., 2013, U.S. Geological Survey Natural Hazards Science Strategy–Promoting 

the Safety, Security, and Economic Well-Being of the Nation: 

U.S. Geological Survey Circular, 1383–F, 79 p.

Hrvoic, Ivan and Hollyer, G.M., 2005, Brief review of 

quantum magnetometers: Ontario, Canada, GEM Systems 

Technical Papers, 15 p.

Iyemori, T. and Rao, D.R.K., 1996, Decay of the Dst field of 

geomagnetic disturbance after substorm onset and its implication to storm-substorm relation: Annales Geophysicae, 

vol. 14, p. 608–618.

Jankowski, Jerzy, and Sucksdorff, Christian, 1996, Guide for 

magnetic measurements and observatory practice: Warsaw, 

Poland, International Association of Geomagnetism and 

Aeronomy, 235 p.

Lay, E.H., Holzworth, R.H., Rodger, C.J., Thomas, J.N., 

Pinto, O. and Dowden, R.L., 2004, WWLL global lightning detection system—Regional validation study in 

Brazil: Geophysical Research Letters vol. 31, L03102, 

doi:10.1029/2003GL018882.

Love, J.J., 2008, Magnetic monitoring of Earth and space: 

Physics Today, vol. 61, no. 2, p. 31–37.

Love, J.J., Applegate, David and Townshend, J.B., 2008, Monitoring the Earth’s dynamic magnetic field: U.S. Geological 

Survey Fact Sheet 2007–3092.

Love, J.J. (ed.), 2009, Proceedings of the XIIIth IAGA Workshop on geomagnetic observatory instruments, data acquisition, and processing: U.S. Geological Survey Open-File 

Report 2009–1226, 271 p.

Love, J.J. and Finn, C.A., 2011, The USGS Geomagnetism 

Program and its role in space weather monitoring: Space 

Weather, vol. 9, S07001, doi:10.1029/2011SW000684.

Love, J.J. and Chulliat, Arnaud, 2013, An international 

network of magnetic observatories: Eos Transactions of 

the American Geophysical Union, vol. 42, p. 373–384, 

doi:10.1002/2013EO420001.

Love, J.J., Rigler, E.J., Pulkkinen, Antti and Balch, C.C., 2014, 

Magnetic storms and induction hazards: Eos Transactions 

of the American Geophysical Union, vol. 95, p. 445–446, 

doi:10.1002/2014EO480001.

Mayaud, P.N., 1980, Derivation, meaning, and use of geomagnetic indices: American Geophysical Union, Washington, 

D.C., Geophysical Monograph 22, 154 p.

Narod, B.B. and Bennest, J.R., 1990, Ring-core fluxgate magnetometers for use as observatory variometers: Physics of 

the Earth and Planetary Interiors, vol. 58, p. 23–28.

NBS, 1963, New geomagnetic observatory: National Bureau 

of Standards Technical News Bulletin, vol. 47, p. 171.

NSTC, 2015, National space weather strategy: Washington, 

D.C., Executive Office, National Science and Technology 

Council, 13 p.

NSWP, 2010, National Space Weather Program strategic plan: 

Silver Spring, Md., Federal Coordinator for Meteorological 

Services and Supporting Research, FCM-P30-2010, 24 p.

Owolabi T.P., Rabiu A.B., Olayanju G.M., and Bolaji O.S., 

2014, Seasonal variation of worldwide solar quiet of 

the horizontal magnetic field intensity: Applied Physics 

Research, vol. 6, p. 82–94, doi:10.5539/apr.v6n2p82.

Primdahl, F., 1979, The fluxgate magnetometer: Journal of 

Physics E—Scientific Instruments, vol. 12, p. 241–253, 

doi:10.1088/0022-3735/12/4/001.

Pulkkinen, Antti, Amm, Olaf, Viljanen, Ari, and BEAR Working Group, 2003, Separation of the geomagnetic variation 

field on the ground into external and internal parts using 

the spherical elementary current system: Earth Planets and 

Space, vol. 55, p. 117–129, doi:10.1002/2013SW000990.

Pulkkinen, Antti, Lindahl, Sture, Viljanen, Ari, and Pirjola, 

Risto, 2005, Geomagnetic storm of 29–31 October 2003—

Geomagnetically induced currents and their relation to problems in the Swedish high-voltage power 

transmission system: Space Weather, vol. 3, S08C03, 

doi:10.1029/2004SW000123.

Rasson, J.L., 2007, Observatories, instrumentation, in Encyclopedia of Geomagnetism and Paleomagnetism (Gubbins, David, 

and Herrero-Bervera, Emilio, eds.): Springer, p. 711–713.

Rigler, E.J., Balch, C.C., and Wiltberger, M.J., 2014, Dynamic 

geomagnetic hazard maps in space weather operations, 

Abstract: Eos Transactions of the American Geophysical 

Union, vol. 95, SM31A-4178. 

Thomson, A.W.P., McKay, A.J., Clarke, Ellen and Reay, S.J., 

2005, Surface electric fields and geomagnetically induced 

currents in the Scottish Power grid during the 30 October 

2003 geomagnetic storm: Space Weather, vol. 3, S11002, 

doi:10.1029/2005SW000156

White, T.C., Sauter, E.A. and Stewart, D.C., 2008, Challenges in 

the development of the automated coil calibration system at the 

Boulder Magnetic Observatory, in Proceedings of the XIIIth 

IAGA Workshop on geomagnetic observatory instruments, 

data acquisition, and processing, Abstract—Golden, Colo.: 

U.S. Geological Survey.

White, T.C., 2009, Total field sensor comparison, in Proceedings 

of the XIIIth IAGA Workshop on geomagnetic observatory 

instruments, data acquisition, and processing (Love, J.J., ed.): 

U.S. Geological Survey Open-File Report 2009–1226, p. 9–13.

White, T.C., Sauter, E.A. and Stewart, D.C., 2014, Discovery and 

analysis of time delay sources in the USGS personal computer 

data collection platform (PCDCP) system: U.S. Geological 

Survey Scientific Investigations Report 2014–5045, 24 p.

Worthington, E.W., Sauter, E.A. and Love, J.J., 2009, Analysis of USGS one-second data, in Proceedings of the XIIIth 

IAGA Workshop on geomagnetic observatory instruments, 

data acquisition, and processing (Love, J.J., ed.): U.S. Geological Survey Open-File Report 2009–1226, p. 262–267.
Publishing support provided by:

Denver Publishing Service Center, Denver, Colorado

For more information concerning this publication, contact:

USGS Geomagnetism Program

Box 25046, MS 966

Denver, CO 80225-0046

(303) 273-8475

Or visit the Geomagnetism Program Web site at:

http://geomag.usgs.gov/

This publication is available online at:

http://dx.doi.org/10.3133/ofr20151125
Love and others—The Boulder Magnetic Observatory—Open-File Report 2015–1125

ISSN 2331-1258 (online)

http://dx.doi.org/10.3133/ofr20151125