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A 125 Year History of Topographic Mapping and GIS
USGS Publication: History of the Topographic Branch (Division)
On December 4-5, 1884, John Wesley Powell addressed the U.S. Congress seeking authorization for the U.S. Geological Survey (USGS) to begin systematic topographic mapping of the United States. During the next 125 years, mapping techniques evolved from field surveys through photogrammetry to the computer-based methods currently used, and the scales and content of the topographic maps changed. It is the purpose of this two-part article to provide details of the USGS mapping processes through time and to help demonstrate that innovations by USGS employees and provision of public domain geospatial data helped spur the evolution and development of digital geographic information systems (GIS) and the commercial market for geospatial data and products of today. This first article describes topographic mapping developments prior to widespread use of GIS.
In the late 19th century, surveyors created topographic maps in the field. A series of points were measured in the field using tape and compass traverses with elevations determined with an aneroid barometer, and used in a process known as field sketching to draw a terrain representation using contours. The introduction of the planetable and alidade, which could measure vertical angles, point positions, and elevations much more rapidly, greatly increased the accuracy of data shown on topographic maps, but still required the surveyor to field sketch the contours after control points had been identified. The aid of a visual three-dimensional model in the office to construct the surface representation awaited the development of photogrammetry.
During this time, USGS maps were created at scales of 1:250,000 for 1-degree areas and 1:125,000 for 30-minute areas. The scales were increased with time and by 1894, most of the maps were 15-minute areas and produced at a scale of 1:62,500. Features shown on the maps included civil divisions of state, county, township, and cities or villages; public works including railroads, tunnels, wagon roads, trails, bridges, ferries, fords, dams, canals, and acequia; hypsography with contours and floodplain representations; and miscellaneous features of forest, sand, and sand dunes.
The reproduction of maps from the original field sketches used a three-color lithographic printing process based on copper plates. The image of the topographic features was engraved on the copper plates. A three-color process was used with civil divisions and public works in black, hydrography in blue, and hypsography and miscellaneous features in brown.
USGS cartographers commissioned for service in the Army Corps during World War I brought back knowledge of aerial photography. Throughout the 1920s, the USGS experimented with photogrammetry, but it was not until the 1930s during the Great Depression, when the Tennessee Valley Authority’s (TVA) need for complete topographic maps of the entire Tennessee Valley and time constraints of the mapping, led the USGS to establish a Multiplex mapping office in Chattanooga, Tennessee.
After orienting the planetable and leveling the alidade, an early USGS topographer takes measurements while his assistant records the information on a field sketch.
The ability to view a three-dimensional terrain surface by doubly reflecting the overlap area, or stereomodel, of a pair of stereophotos in a Multiplex stereoplotter, effectively replaced the requirements of field sketching. An operator could fix a vertical floating mark at a preset elevation in the stereomodel and trace contours to represent the terrain. Similarly, tracing a road or other planimetric feature in the stereomodel but allowing the mark to change elevation along the feature provided recording of all required planimetric features for the topographic map.
After 1942, the USGS used pen and ink drawings that were photographed to film separations, eliminating the need for copper plates. After a few years the pen and ink process was replaced by the use of engravers and scribecoat. The scribecoat replaced the film in the pen and ink process and could be used directly for photographic reproduction.
The 1:24,000-scale 7.5-minute mapping program resulted from demand for more detail on the topographic maps. With the larger scale, the USGS included almost 200 features separated into color groups for the five color plates to be used in the film-based reproduction process. The five plates included cultural features, such as roads shown with casings, buildings, and much of the type used on the map on a black plate; road fills, urban tints, Public Land Survey lines, and other features on a red plate; woodland tint and other vegetation on a green plate; hydrographic features on a blue plate; and contours, depressions, and other hypsographic features on a brown plate. The color separations were composited on a five-color lithographic press.
The USGS widely adopted photogrammetry as a part of the mapping process after World War II and USGS employees developed innovations in the production workflow and in the instrumentation. Russell K. Bean of the USGS invented the "Ellipsoidal Reflector Projector" (ER-55) for which he was awarded a patent in 1956. The ER-55 became a replacement for the Multiplex stereoplotter for the USGS and was later manufactured and marketed by Baush and Lomb as the Balplex stereoplotter. Also, during this period, the Kelsh stereoplotter, invented by Harry T. Kelsh of the USGS, was widely adopted. A USGS innovation for the Kelsh and other optical projection stereoplotters was StereoImage Alternation (SIA), which operators often called the "squirrel-cage" because of the rotating shutters inside a short metal tube; when viewed with the naked eye, the SIA sequentially presented the left photo to the left eye and the right photo to the right eye to form the stereomodel.
Additional innovation and developments provided the USGS with solutions for stereoplotting, aerotriangulation, point measurement, and other photogrammetric operations. The Kelsh stereoplotters were used in areas of moderate to high relief, but low relief areas, such as along the coasts and large parts of the Great Plains, required the capabilities of the "heavy" stereoplotters that used projection by mechanical rods. These stereoplotters included the Wild A8, B8, the Kern PG-2, and others of German, Swiss, and Italian manufacture. The Kelsh and the heavy plotters were used until completion of the 7.5-minute topographic map series in 1991; however, additional innovations led to the concept and technology for producing orthophotos in the 1960s.
A map engraver carefully prepares one of the three lithographic stones required for the 1915 reprint of the Donaldsonville, Louisiana, topographic map.
The development by the USGS of the orthophoto concept and building of a practical orthophotoscope by Russell K. Bean, with a patent in 1959, led to the production of orthophotoquads – rectified aerial photos. Orthophotos became a standard product of the USGS and later served as a base for the 7.5-minute topographic maps.
Many other innovations affected the mapping process such as the measurement of angles in the field with instruments including transits and theodolites. Distances were measured with electronic distance measuring (EDM) units using microwave technology and, later, lasers.
The development of computers may represent the greatest technological innovation to change the mapping process and USGS employees were quick to embrace this technology. In the 1960s, the USGS developed the AutoPlot, a device that used stepping motors to move scribing engravers to create a scribecoat negative of the topographic map neat line (latitude and longitude lines that bound the quadrangles) and horizontal pass points.
After 1970, the USGS embarked on three different tracks using digital technology. First, a massive program to manually digitize existing maps to create a product with an arc/node data model, known as a Digital Line Graph (DLG), was initiated. During the same time, the advances in photogrammetric technology that generated an orthophotograph were used to simultaneously produce a Digital Elevation Model (DEM). Both DLGs and DEMs were placed in the public domain.
The second track was the automation of the map production operation. The Digital Cartographic Software System (DCASS) development included retro-fitting analog stereoplotters, such as the PG-2, with three-axis digitizers to collect and record the x,y coordinates and attributes of geographic features from the stereomodel to a magnetic tape. The tape later was used to drive a large format automatic plotter, a Gerber 4477, to engrave the map data onto the scribecoat, or to drive a photohead device to expose a film negative. A cartographic interactive editing capability, referred to as the Graphic Map Production System (GRAMPS), also was developed by USGS employees. The scribecoats or film negatives from the final editing process became the color separations necessary for the five-color press to create the lithographic map.
The final track was the development of a land cover data generating program, Land Use Data Analysis (LUDA). The program also developed software, the Geographic Information Retrieval and Analysis System (GIRAS), to support vector graphics and analysis from an arc/node data model. These data became the first complete land cover dataset for the conterminous 48 states and, as with the DLG and DEM data, were provided in the public domain.
Throughout this period, USGS scientists were developing innovative computer-based data products and hardware/software systems that were made directly available to the public. A software example that persists today is the General Cartographic Transformation Package (GCTP), written in the 1970s by Atef Elassal, a USGS employee. The computer code in FORTRAN IV (later converted to C and in 2009 available in C++) can transform data to any of 21 different map projections. This package was the basis of map projection packages that became a part of the GIS software, which would have its commercial debut in the 1980s.