Defense Mapping Agency Research Articles

Historical development of SIRGAS

Abstract The Geodetic Reference System for the Americas (Sistema de Referencia Geodésico para las Américas, SIRGAS) was initiated in 1993 for South America at an international conference organised by the International Association of Geodesy (IAG), the Pan-American Institute for Geography and History (PAIGH), the Deutsches Geodätisches Forschungsinstitut (DGFI), and the U.S. Defense Mapping Agency (DMA) in Asunción, Paraguay. The corresponding South American reference network was observed in 1995 by a ten-day GPS campaign at 58 stations. The network was extended to Central and North America in 2000 and immediately afterwards converted to a frame of continuously observing GNSS stations instead of short-term campaigns. The linear station position changes (velocities) were estimated by a multi-year least squares adjustment of weekly solutions, the first being published in 2002. The total set of station velocities served for the computation of continuous surface deformation models, the first over South America was published in 2005. Today, SIRGAS is accepted by most of the American states as the official geodetic reference frame. Besides the product generation (station positions, velocities, and surface deformation), SIRGAS is active in education and training offering schools and workshops for students, surveyors, and other stakeholders.

Transforming between WGS84 Realizations

The World Geodetic System 1984 (WGS84) has been consistent with the International Terrestrial Reference Frame (ITRF) since 1994. After the original release of WGS84 in 1987 by the Defense Mapping Agency (since superseded by the National Geospatial-Intelligence Agency, NGA), there have been six subsequent realizations of the frame, designated WGS84 (G730), WGS84 (G873), WGS84 (G1150), WGS84 (G1674), WGS84 (G1762), and WGS84 (G2139). Users of WGS84 often fail to document metadata indicating the realization and epoch related to their data collections. As a result, when transforming between realizations or between other reference frames, the transformation can lead to incorrect results. We aim to bring awareness to the nature of WGS84 and the ambiguity in how it is defined. An internally consistent set of transformation parameters is derived that allows for transformation between the WGS84 realizations and other global reference frames while accounting for nuances and inconsistencies in the published literature. The derivations are based on existing (though not easily discoverable) information. Transformation accuracy is evaluated through comparison to other software and NGA-published GPS tracking station coordinates. After accounting for plate tectonic motion, the estimated uncertainties average ±0.03 m horizontally and ±0.08 m vertically for transformations involving all realizations other than the original WGS84. Uncertainties are at the meter level for transformations that include the original WGS84. If plate motion is ignored, the horizontal uncertainties can increase by several decimeters, depending on location within a plate.

Updating Topographic Maps at Scale 1:250000 for Libyan Territory Using Quantum GIS (QGIS) and Open Geospatial Data: Libya Topo-Project

From the beginning of the twentieth century, topographic maps for the Libyan state carried out by various compilers, where the first mapping was carried out by the Italian Military Geographical Institute, the Soviet Union Military, and the U.S. Army, followed by mapping carried out by the Libyan state from the 1950s to the 2000s. Most of these maps have not been digitized and updated using the techniques of geographic information systems and remote sensing. This paper discusses on the objectives, methodology and results of the Libya Topography Project, “Libya Topo” for updating the previously compiled topographical map at scale, 1:250000. Open spatial data from different platforms (OSM, Logistics Cluster, Landsat 8 satellite imagery, and SRTM data, etc.). Also, POIs extracted from previously compiled topographic and geological maps. Spatial database for each UTM zone created to store the features and raster. As for the cartographic style, the map layout adopted is the style of the U.S. Defense Mapping Agency maps. The results of the project are an update of 121 topographical map sheets using Quantum (GIS), those will be freely available for the interested users on request (e.g., environmentalists, academics, and university students, etc.).

Necrology: Richard Rainier Randall

Dick Randall, a well-known figure in the world of toponymy, passed on March 14, 2015. Dick demonstrated continuously that he was multifaceted excelling in numerous and diverse activities. He was always eager to help and assist and was well respected by all who knew him and through his work those who did not know him. Dick was born in Toledo, Ohio on July 21, 1925. He moved to Washington, D.C in 1936 when his father was appointed by President Franklin D. Roosevelt as advisor to the National Resources Board. Dick earned an A.B. in 1948 and an M.A. in 1949 each from George Washington University. In 1955, Dick received his Ph.D. from Clark University (Worcester, Massachusetts). He also studied in 1953 and 1954 as a Fulbright Scholar at the University of Graz in Austria. Dick served his nation in the 94th Infantry during World War II where he was awarded the Combat Infantryman Badge and received the Bronze Star and four Battle Stars. Dick’s career was always in various aspects of geography and cartography specializing in map editing, quality assurance, and applied toponymy. Although Dick began his career formally with the Central Intelligence Agency, he spent much of 1943 with the Alaska Branch of the U.S. Geological Survey interpreting aerial photographs. He began his formal career at the Central Intelligence Agency where he worked from 1955 to 1961 specializing in editing and later as a specialist in matters of Eastern Europe. In 1961 he became the representative in Washington, D.C. for Rand McNally & Company where he was instrumental in overseeing data collection for Rand McNally’s extensive line of products. His work was highlighted in 1969 when he designed the series of maps showing the world’s oceans and water bodies for inclusion in Rand McNally’s Cosmopolitan Atlas of the World. In 1973, Dick became The Geographer at the Defense Mapping Agency (now National-Geospatial Intelligence Agency) where some of his responsibilities included the foreign geographic names program for the federal government and serving as the Executive Secretary of the U.S. Board on Geographic Names. He retired from his professional career at the Defense Mapping Agency in 1993, but remained active in various professional organizations including the American Congress on Surveying and Mapping where he established its press relations program in 1966 and the Association of American Geographers where he was heavily involved with that organization’s Careers in Geography Program. He also maintained membership in the American Geographical Society and the American Name Society. Dick was also a long-time active fellow of the Explorers Club and member of the Cosmos Club. At the Washington Chapter of the

New shoreline map‐drawing data available

A new shoreline database for making geophysical maps is now available to software developers and should expedite the map‐drawing process considerably. The new database, known as Regionally Accessible Nested Global Shorelines (RANGS), attempts to combine the best of the two sets of data most often used in recent years. It follows its forerunners, World Vector Shoreline (WVS) and global self‐consistent hierarchical high‐resolution shorelines (GSHHS),in providing coastline information for computing geophysical maps.Software tools for such maps often require such information, and many make use of WVS data, originally issued by the U.S. Defense Mapping Agency in 1988. WVS data are organized in 1°×1° cells covering the entire globe and depicting either only water or only land or coastlines.

New high‐resolution model developed for Earth's gravitational field

After 3 years of intense work by some two dozen collaborating scientists at three institutions and after scores of evaluation tests, the Earth Gravitational Model 1996 (EGM96) was completed and released to the scientific community in September 1996. This model was developed jointly by the NASA Goddard Space Flight Center (GSFC), the National Imagery and Mapping Agency (NIMA, formerly the Defense Mapping Agency), and The Ohio State University.EGM96 provides a more accurate reference surface for the topography, improves models of the ocean circulation, improves orbit determination for low‐orbiting satellites, and contributes to global and regional studies in tectonics and geodynamics. The new spherical harmonic model, is complete to degree 360, corresponding to a global resolution of about 55 km. EGM96 incorporates newly released surface gravity data from around the globe, over three decades of precise satellite tracking data and altimeter measurements of the ocean surface from the TOPEX/POSEIDON, ERS‐1 and GEOSAT missions. Figure l a shows a global map of the geoid undulations implied by EGM96, while Figure l b shows the corresponding gravity anomaly field.

Missouri Mineral Locality Index

Click to increase image sizeClick to decrease image size Additional informationNotes on contributorsMark D. SherwoodMark Sherwood, who has a bachelor of science in chemistry has been collecting for thirty-five years and specializes in species and micromount sizes. Glenn Williams, who has a bachelor of science in geology, is a retired cartographer with the Defense Mapping Agency in St. Louis. His collecting interest embraces specimens of all sizes, with emphasis on thumbnails.

Predicting Southern Appalachian overstory vegetation with digital terrain data

Vegetation in mountainous regions responds to small-scale variation in terrain, largely due to effects on both temperature and soil moisture. However there are few studies of quantitative, terrain-based methods for predicting vegetation composition. This study investigated relationships between forest composition, elevation, and a derived index of terrain shape, and evaluates methods for predicting forest composition. Trees were measured on 406 permanent plots within the boundaries of the Coweeta Hydrologic Lab, located in the Southern Appalachian Mountains of western North Carolina, USA. All plots were in control watersheds, without human or major natural disturbance since 1923. Plots were 0.08 ha and arrayed on transects, with approximately 380 meters between parallel transects. Breast-height diameters were measured on all trees. Elevation and terrain shape (cove, ridge, sideslope) were estimated for each plot. Density (trees/ha) and basal area were summarized by species and by forest type (cove, xeric oak-pine, northern hardwoods, and mixed deciduous). Plot data were combined with a digital elevation data (DEM), and a derived index of terrain shape at two sampling resolutions: 30 m (US Geological Survey), and 80 m (Defense Mapping Agency) sources. Vegetation maps were produced using each of four different methods: 1) linear regression with and without log transformations against elevation and terrain variables combined with cartographic overlay, 2) kriging, 3) co-kriging, and 4) a mosaic diagram. Predicted vegetation was compared to known vegetation at each of 77 independent, withheld data points, and an error matrix was determined for each mapping method.

A Comparison of Existing Co-ordinate Transformation Models and Parameters in Australia

Four standard procedures to transform curvilinear co-ordinates from the Australian Geodetic Datum 1984 to the World Geodetic System 1984 are compared. These comprise the Bursa-Wolf model with the national set of seven parameters currently used by Federal and State surveying and mapping authorities, the standard Molodensky model with the five parameters used by the United States Defense Mapping Agency, the simple three-parameter model with the origin shifts taken from the Bursa-Wolf and standard Molodensky models, and the multiple regression equations as determined by the Defense Mapping Agency. The differences between the resulting coordinates can reach 4.2 metres over continental Australia, which has implications for the final approach adopted to transform to the Geocentric Datum of Australia. The arguments are presented in favour of more suitable transformation strategies using projective transformation models, which are able to simultaneously correct any known errors existing in the Australian Geodetic Datum. These models also allow the direct transformation of both Australian Geodetic Datum 1966 and Australian Geodetic Datum 1984 co-ordinates in a single procedure, which will be of benefit to those States which rely upon older geodetic datums.

A transformation procedure for digitising Defense Mapping Agency air navigation charts

The mathematical transformation for converting coordinates digitised from the Defense Mapping Agency 1:1 million Operational Navigation Chart, the 1:2 million Jet Navigation Chart and the 1:500,000 Tactical Pilotage Chart map sheets into latitudes and longitudes is described. A least squares adjustment is employed in order to improve the accuracy, and to provide a check on the quality of the digitisation.

A comparison of existing coordinate transformation models and parameters in Australia

Editor's note: This paper is a joint publication by the Institution of Surveyors, Australia and the Mapping Sciences Institute, Australia. Four standard procedures to transform curvilinear co-ordinates from the Australian Geodetic Datum 1984 to the World Geodetic System 1984 are compared. These comprise the Bursa-Wolf model with the national set of seven parameters currently used by Federal and State surveying and mapping authorities, the standard Molodensky model with the five parameters used by the United States Defense Mapping Agency, the simple three-parameter model with the origin shifts taken from the Bursa-Wolf and standard Molodensky models, and the multiple regression equations as determined by the Defense Mapping Agency. The differences between the resulting co-ordinates can reach 4.2 metres over continental Australia, which has implications for the final approach adopted to transform to the Geocentric Datum of Australia. The arguments are presented in favour of more suitable transformation stra...

An optimal vertical reference plane correction algorithm for multiple source digital elevation models

The JPL Cartographic Group is currently constructing a worldwide database of digital elevation at nominal 100 m postings, using multiple sources of elevation data available from the U.S. Defense Mapping Agency, including DTED Level-1, and DCW hypsography. In the process of constructing the database, vertical shear anomalies were observed on 1 degree cell boundaries. The source was attributed primarily to uncontrolled variations in the vertical reference surface used from cell to cell, varying by as much as 80 m. This paper describes algorithms developed to merge these problematic cells into a morphologically consistent database, while preserving the local accuracy estimates.

Satellite-view biases in retrieved surface temperatures in mountain areas

Ground surface temperatures retrieved from satellite data taken in mountain areas may have biases that depend strongly on the satellite viewing angle and the time of clay. Biases occur whenever there is a correlation between the viewing angle and the temperatures of subpixel mountainsides, such as when the satellite's view directly faces the most brightly sunlit slopes. This paper reports simulations of this satellite-view bias effect for mountain terrain in central and southwestern Colorado and the southern Sierra Nevada in California. Surface temperatures for the simulations were computed by using a mesoscale numerical weather prediction model with a parameterization for terrain features that are at a scale finer than. the model grid resolution. The representation of terrain in the simulations was based on elevation. data with high resolution (30 m) from U.S. Geological Survey Digital Elevation. Map data sets. Biases as large as 9 C° were found while assuming a satellite sensor resolution of 14 km. Even larger biases were found with finer sensor resolutions. These biases are substantially larger than those that had previously been found from modeling with terrain data at about 90 m -resolution (3″ latitude/longitude) from the Defense Mapping Agency. The simulations suggest that satellite-view; biases could cause substantial local errors when surface temperature retrievals are used for climate diagnosis, weather analysis, soil moisture estimation, or geologic mapping.

Managing the US Navy's first OO digital mapping project

In the late 1980s the Defense Mapping Agency began converting their paper maps into digital format. A military standard known as Vector Product Format emerged as the format for storing digital vector data. The VPF relational data model, however, has problems representing complex spatial data. In 1991, the US Navy, a DMA database user, began investigating how object technology could improve its digital maps. This research led to the development of the Object Vector Product Format, an object-oriented approach to viewing and editing digital maps and charts. By combining multiple relational databases into a single OO database, OVPF offers users such key advantages as the ability to immediately update and modify the content of the original data. Over the course of developing OVPF we have also learned some valuable lessons about managing OO projects. Our experiences have given us insight into some important risk-management techniques, including how to manage the expectations of decision-makers and sponsors and how to implement effective training methods. Managing the OVPF project was much more rewarding than most due to the greatly increased productivity offered by an OO approach.

Analysis and evaluation of the NASA/JPL TOPSAR across-track interferometric SAR system

We have evaluated the accuracy of digital elevation models (DEM's) generated by the JPWNASA TOPSAR synthetic aperture radar interferometer instrument by acquiring topographic radar data in the summer of 1992 over the National Training Center, near Ft. Irwin, California, and comparing the measurements to a very accurate digital elevation model derived for this area by the US. Army Topographic Engineering Center (TEC). Fiducial corner reflectors were deployed in the area, and their locations were determined to cm accuracy by the Defense Mapping Agency (DMA). DEM’s generated from the acquired radar data were rotated and translated to precisely overlay the reference DEM, allowing an analysis of the achieved height accuracy. We present here a detailed description of horizontal and vertical errors and their characteristics. The standard deviation measured over a 5.6 x 7 km area was approximately 2 m, the corresponding figures for relatively flat areas were in the 1-2 meter range and for mountainous areas in the 2-3 meter range, consistent with theoretical expectations. We also discuss key factors that presently limit the system performance

Transformation between SLR/VLBI and WGS-84 reference frames

In geodetic and geophysical applications of GPS, it is important to realize the ephemerides of the GPS satellites and the coordinates of station positions in a consistent reference system. At present, more than one reference system is being used by various GPS users depending on their specific applications. The WGS-84 and various reference frames based on satellite laser ranging (SLR), very long baseline interferometry (VLBI), or a combination of SLR and VLBI are the most commonly used in high precision geophysical applications. The WGS-84 is widely used in applications which rely on the GPS broadcast ephemeris. Station coordinates estimated in one system may have to be transformed to another for further use or for evaluation/comparison purposes. This paper presents a seven-parameter transformation between the WGS-84 and SLR/VLBI reference frames. The GPS double-differenced phase measurements for two consecutive weeks from a set of five Defense Mapping Agency (DMA) sites (defined in the WGS-84 frame) and from an augmented set of fifteen CIGNET sites (defined in the SLR/VLBI frame) were processed in a least squares estimation scheme to determine station coordinates, from which the transformation parameters were determined. A scale difference of about 0.2 ppm and an orientation difference in longitude of about 31 milliarcseconds were found to be the only parameters of significance between the adopted SLR/VLBI and the WGS-84 frames. Transformation between WGS-84 and the ITRF90 is also included, in which the scale difference is the same as before but the longitude rotation is about 16 mas.

Fox in the chicken coop

While there is a push to transfer Earth‐observing data to the commercial sector, such initiatives do not include the illegal sale of restricted information from the U.S. Department of Defense. Unfortunately Andrew N. Fox, a former Cornell University graduate student, had to learn this distinction the hard way. Fox has pleaded guilty to using such data for a profitmaking scheme. Fox reportedly was part of a team of professors and students in Cornell's geological sciences department that was using Defense Mapping Agency data to study the topography of various regions.

The Defense Mapping Agency GPS Tracking Network

Since the early 1960s, the Defense Mapping Agency (DMA) and its predecessors have been involved in satellite geodesy and the operation of satellite tracking networks to support satellite geodesy. In the mid-1980s, DMA developed and deployed a GPS tracking network. This tracking network consists of five stations deployed worldwide, which continuously collect and regularly communicate dual-frequency range and phase measurements and meteorological data to the DMA satellite ephemeris processing facility. On a weekly basis, these data, along with data from the GPS Operational Control Segment monitor stations, are processed to produce precise ephemerides that provide quality assurance for the GPS broadcast ephemerides and support the DMA precise point positioning program. This paper describes the development of DMA's GPS tracking network, and efforts currently under way to automate the stations and provide the capability to operate in an anti-spoofing environment.

Effect of broadcast and precise ephemerides on estimates of the frequency stability of GPS Navstar clocks

AbstractFrequency stability analysis of on‐orbit Navstar clocks is performed by the Naval Research Laboratory using both the broadcast and the precise post‐processed ephemerides. The phase offset between the Navstar clock and the reference clock is computed from pseudorange measurements obtained by dual‐frequency GPS receivers at the five GPS monitor sites and at the U.S. Naval Observatory precise‐time site. The broadcast ephemerides are generated at the GPS master control station by a Kalman filter using data collected from the five GPS monitor stations. The precise post‐processed ephemerides are generated by the Defense Mapping Agency (DMA) using data collected from the GPS monitor sites and from five additional DMA monitor sites. In this paper the frequency stability is estimated for two Navstar caesium clocks–a Block I caesium clock (Navstar 9) and a Block II caesium clock (Navstar 23)–using both the broadcast and the precise ephemerides. A significant improvement in the estimate of the frequency stability of the Block II clocks has been achieved using the precise ephemeris.

Testing the precision lightweight GPS receiver

Innovative field testing techniques are employed at Holloman Air Force Base to help the Global Positioning System (GPS) NAVSTAR Joint Program Office (JPO) test the Precision Lightweight GPS Receiver (PLGR). Characterizing the PLGR's accuracy in dynamic environments is of prime importance but testing also prescribes the evaluation of its ability to receive differential GPS corrections, real time, and its Electronic Counter Counter Measures. To meet these goals, the 46th Test Group provides the C-12 cargo aircraft for flight testing, an instrumented test van for mobile testing, the High Speed Test Track for high velocity testing, a UH-1 helicopter for rotor blade modulation testing, and special PC laptops for ground troop testing. All of these test capabilities utilize Holloman's well instrumented test environments with thousands of surveyed sites validated by the Defense Mapping Agency. This paper emphasizes the testing techniques that are helping to define Test & Evaluation methodologies for the changing world where Global Positioning with NAVSTAR is becoming a reality.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>