Topography Data

[Glynis Waughtal]

Topographicdata are information about the elevation of the surface of the Earth. Two such data types are commonly used with GeoPads. The first are data that represent the information typically found on a topographic quadrangle map, such as contour lines, roads, streams, railroads, towns, etc. For simplicity, this first category of data will be referred to as digital topographic map data. The second are grids of data, for which each cell in the grid represents the elevation at a certain point on the Earth. These data are commonly referred to as Digital Elevation Models or DEMs.

Digital topographic map data exists for the United States in both vector (points, lines and polygons) and raster (image) formats. The vector topographic data are called Digital Line Graphs (DLGs) while the raster topographic data are called Digital Raster Graphics (DRGs). Availability of each are described below.

Digital line graphs (PDF fact sheet) are files that contain the point, line, and polygon data found on a traditional paper topographic map, including the Public Land Survey System (township and range boundaries), contour lines, rivers, lakes, roads, railroads, towns, land cover, survey control points, etc. The advantage to using DLGs in a GIS setting is that the vector features can be rendered at any scale, such that zooming in and out on the map does not change the quality of the topographic data representation. The disadvantages of the DLG format are that importation of the data to a GIS requires more effort than importing a DRG raster image, and that the DLG data are quite large, sometimes slowing down the screen refresh rate of the GIS software, and that not all data layers are available for all topographic map quadrangles. Data layer projections for DLG data vary from state to state. DLG data is available in three series.

Digital Raster Graphics are also available for a large number of commercial distributors for a fee, and many states choose to distribute DRGs through a state-supported web portal. An Internet search on a state name and the keywords 'geospatial data' or 'gis data' will return many useful resources.

Digital Elevation Models (DEMs) are gridded representations of the surface of the Earth where each pixel in the grid contains an elevation value. Resolution of DEMs is often reported in radial measurements, such as arc-seconds.

Topographic data created by airborne or space-based techniques (e.g. LiDAR or IfSAR, including the SRTM DEM data) have the advantage of being generally smooth and continuous data sets. The National Elevation Dataset is derived from digitization of USGS topographic maps, and the gridded data derived from this technique can be prone to a number of data artifacts. On the other hand, Synthetic Aperture Radar is absorbed by water and snow and generally does not return elevation data from these surfaces. Airborne and space-based techniques may also have difficulty in steep, rugged topography. A comparison of datasets may be necessary to find the most appropriate type for a particular project.

TNM Access Application Programming Interface (API) provides developers with programmatic access to historical topographic maps and US Topo as well as other geospatial data products of The National Map.

The newest USGS topo map web app gives the public the opportunity to create custom topographic maps on demand. The online application is called topoBuilder and the output maps are known as OnDemand Topos.

topoBuilder is a public web application released by the National Geospatial Program that enables users to request customized USGS-style topographic maps, known as an OnDemand Topo, that utilize the best available data from The National Map.

The U.S. Geological Survey's National Geospatial Program developed the GNIS in support of the U.S. Board on Geographic Names as the official repository of domestic geographic names data, the official vehicle for geographic names use by all departments of the Federal Government, and the source for applying geographic names to Federal electronic and printed products.

The Shuttle Radar Topography Mission (SRTM) payload flew aboard the Space Shuttle Endeavour during the STS-99 mission. SRTM collected topographic data over nearly 80% of Earth's land surfaces, creating the first-ever near-global dataset of land elevations.

The SRTM payload consisted of two radar antennas, one located in the shuttle's payload bay and the other installed on the end of a 200-foot mast that extended from the payload bay. Each SRTM radar assembly contained two types of antenna panels: C-band and X-band. C-band radar data were used to create near-global topographic maps of Earth called Digital Elevation Models (DEMs).

Data from the X-band radar were used to create slightly higher resolution DEMs but without the global coverage of the C-band radar. The two radar datasets were combined to create interferogramatic maps of scanned areas. SRTM measurements took place February 11-22, 2000.

TopoView highlights one of the USGS's most important and useful products, the topographic map. In 1879, the USGS began to map the Nation's topography. This mapping was done at different levels of detail, to support various land use and other purposes. As the years passed, the USGS produced new map versions of each area. TopoView shows the many and varied topographic maps of each of these areas through history. This can be particularly useful for historical purposes, such as finding the names of natural and cultural features that have changed over time.

This interface was created by the National Geologic Map Database project (NGMDB), in support of topographic mapping program managed by the National Geospatial Program (NGP). Geologic mapping and topographic mapping at the USGS have a long tradition together (see 1888 report). The NGMDB project is proud to assist the NGP in bringing these maps to the Web.

The goal of the HTMC, which started in 2011, is to provide a digital repository of USGS 1:250,000 scale and larger (more detailed) maps printed between 1884 (the inception of the topographic mapping program), and 2006. Currently, there are more than 178,000 maps in the HTMC and the collection continues to grow. NGP is accurately cataloging and creating metadata to accompany high-resolution, georeferenced digital files of each of these printed maps.

At present, both the US Topo series and HTMC maps are offered as GeoPDFs through The National Map and the USGS Store. However, additional formats are now offered for evaluation and use through topoView. These include:

The Global Multi-Resolution Topography (GMRT) synthesis is a multi-resolutional compilation of edited multibeam sonar data collected by scientists and institutions worldwide, that is reviewed, processed and gridded by the GMRT Team and merged into a single continuously updated compilation of global elevation data. The synthesis began in 1992 as the Ridge Multibeam Synthesis (RMBS), was expanded to include multibeam bathymetry data from the Southern Ocean, and now includes bathymetry from throughout the global and coastal oceans. GMRT is included in the ocean basemap in Google Earth (since June 2011) and the GEBCO compilation since 2014. Learn more >

additional note: In the past, I used to convert the x-y-z data into IGS surface using commercial CAD software, and then import it into cubit. This approach entails some approximation and it is cumbersome.

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Amante, C. and B.W. Eakins, 2009. ETOPO1 1 Arc-Minute Global Relief Model: Procedures, Data Sources and Analysis. NOAA Technical Memorandum NESDIS NGDC-24. National Geophysical Data Center, NOAA. doi:10.7289/V5C8276M [access date]

Cite as: National Geophysical Data Center, 1999. Global Land One-kilometer Base Elevation (GLOBE) v.1. Hastings, D. and P.K. Dunbar. National Geophysical Data Center, NOAA. doi:10.7289/V52R3PMS [access date].

Many areas multiple candidate datasets, which were compared before final selection and mosaicked into the full global DEM. The CEOS GLOBE Task Team and IGBP-DIS. The final product received peer review on four continents.

I've uploaded my data in both txt and csv file formats, then tried to do "specify points file" with both, but I'm getting the error messages: "no points were found in the file" and "some rows from the file could not be used". The site is relatively flat, but I'm not sure how to fix the issue. Trying to teach myself how through YouTube and forums, but struggling.

Our topographic data is available for use in GIS applications, in the following scales which reflect their level of accuracy and best scale for use. The smaller the scale (i.e. 1:250 000 is a smaller scale than 1:100 000), the fewer features are depicted in the data and naturally they will be less spatially accurate. Geodata is vector data.

1:100 000: At this scale 1cm is equal to 1km. This is the largest scale data provided and is particularly suited for land management and planning applications. Data quality and reliability varies at this scale.

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