GeoData

USGS GeoData

Some of the primary responsibilities of the 

U.S. Geological Survey (USGS) National

Mapping Program (NMP) are to make available

maps, images, spatial data, remote sensing data,

and related information; provide assistance in

selecting, acquiring, and using geographic and

cartographic products; and design, print, and 

distribute maps of the National Atlas. It coordinates Federal topographic mapping and digital

cartographic activities and provides leadership in

the development and advancement of surveying

and mapping technology. 

The primary series of standard digital data types

created by the NMP is known as USGS GeoData.

These data types are as follows:

• Digital Elevation Model (DEM)

• National Elevation Dataset (NED)

• Digital Raster Graphic (DRG)

• Digital Orthophoto Quadrangle (DOQ)

• Digital Line Graph (DLG)

• National Hydrography Dataset (NHD)

• National Land Cover Dataset (NLCD)

• Geographic Names Information System

(GNIS)

This booklet shows samples of the data with brief

descriptions and applications.
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DEM data are records of terrain information in

the form of a sampled array of data at regularly

spaced horizontal intervals. The collection 

methods and sources of DEM data have varied

greatly throughout the history of the product. 

The USGS now uses primarily cartographic

sources rather than photogrammetric sources as

input to the DEM product. Cartographic sources

include contours from DLG hypsography data

and scanned contours from USGS topographic

maps. Photogrammetric sources include the use

of aerial photographs with manual or automated

stereoplotting devices to create DEM’s. 

The USGS currently produces DEM products 

in the following units of coverage: 7.5-minute

DEM, 30-minute DEM, 1-degree DEM, 7.5-

minute Alaska DEM, and 15-minute Alaska DEM.

The most widely used format is the 7.5-minute

DEM, where the area of coverage corresponds

directly to the 1:24,000-scale USGS topographic

map series. The data are stored in a native

(ASCII) file format. 

Applications of DEM Data

DEM data are used in various applications, such

as civil engineering (road design, line-of-sight

operations, site planning, and volumetric calculations in building dams and reservoirs), earth 

sciences (hydrological, slope, and aspect studies,

terrain modeling, and shaded-relief mapping), 

and surveying and photogrammetry (source data

for digital orthophotos and hypsographic data for

topographic mapping).

Additional information about DEM data and the

DEM program is available through the Internet 

at rockyweb.cr.usgs.gov/elevation/.

Shaded-relief map of the contiguous United States 

created from the National Elevation Dataset. 

Digital Elevation Model Data
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National Elevation Dataset

The NED is a new raster product assembled by

the USGS. The NED is designed to provide

national elevation data in a seamless form with a

consistent datum, elevation unit, and projection.

Data corrections were made in the NED assembly

process to minimize artifacts, permit edge

matching, and fill small areas of missing data.

The NED has a resolution of 1 arc-second

(approximately 30 meters) for the conterminous

United States, Hawaii, and Puerto Rico and a

resolution of 2 arc-seconds for Alaska.

NED data sources have a variety of elevation

units, horizontal datums, and map projections. In

the NED assembly process, the elevation values

are converted to decimal meters as a consistent

unit of measurement, the North American Datum

of 1983 (NAD 83) is consistently used as the

horizontal datum, and all the data are recast in a

geographic projection. Older DEMOs have been

filtered during the NED assembly process to

minimize artifacts commonly found in data 

produced by methods that are now obsolete.

Artifact removal greatly improves the quality of

the data. As higher resolution or higher quality

data become available, the NED is updated to

incorporate the best available coverage. The

USGS 7.5-minute and 15-minute digital elevation

products are nearing completion for the conterminous United States and Alaska respectively, and

the NED will soon incorporate these sources. For

the small areas that are not yet covered, the lower

resolution 30-minute and 1-degree USGS DEM’s

were interpolated to obtain values used in the

NED. A customer can identify the requested area

graphically through the Internet browser. That

area of interest will be extracted from the NED

and from the spatially referenced metadata and

formatted for delivery. The data will be available

to download from the Internet in the Spatial Data

Transfer Standard (SDTS) format, using file

transfer protocol (ftp), and it will also be available on standard distribution media. 

Applications of the NED

Elevation data are an essential part of many earth

science applications. They are used for such

diverse purposes as providing shaded-relief

backgrounds, establishing stratification in land

cover classification, doing geometric and radiometric correction of remotely sensed data, indicating landform characteristics such as slope and

aspect, and analyzing synthetic drainage networks

and watershed delineations through the use of

geographic information systems (GIS). More

information on the NED is available through the

Internet at edcnts12.cr.usgs.gov/ned.
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Example of a shaded-relief digital raster graphic showing a part of the Juneau, Alaska,

1:63,360-scale DRG combined with digital elevation model data. This image is intended 
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Digital Raster Graphic Data

A DRG is a scanned image of a USGS topographic map. The resolution of the resulting

image is 250 dots per inch. Standard color values

are maintained for all files, and a total of 13 

colors can be incorporated in any given file. The

file is formatted in the Georeferenced Tagged

Image File Format (GeoTIFF), which is easily

manipulated by most imaging software. The

scanned image includes all of the original map

collar information. The image inside the map

neatline is referenced to the Universal Transverse

Mercator (UTM) projection. The datum for the

file will be the same as it was for the source map

(NAD 27 or NAD 83). File sizes are typically

between 4 and 25 megabytes, depending on the

density of information within the respective map.

Applications of DRG Data

The DRG is an effective mapping tool, but its full

potential for digital applications is realized when

it is used in combination with other data, such as

DOQ and DLG data, for digital map revision. The

DRG can also be combined with a DEM for 

creating shaded-relief products. In addition, the

DRG can be used with a global positioning 

system (GPS) for determining the location of way

points in preparation for field work. The UTM or

geographic coordinates can be determined for

select locations from the DRG and stored in the

GPS unit for future use. Additional information

about DRG data is available through the Internet

at mcmcweb.er.usgs.gov/drg/.

A digital raster graphic image depicting a portion of the Montpelier, Vermont, 1:24,000-scale quadrange.

A combined digital raster graphic and digital orthophoto quadrangle image of a part of the 

Lawrence, Kansas, 1:24,000-scale quadrangle. Each data type has been displayed as 50 percent

of the total image. Applications such as this are used in data revision processes.
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Digital Orthophoto

Quadrangle Data

A DOQ is a computer-generated image of an

aerial photograph, in which image displacement

caused by terrain relief and camera tilts has been

removed. It combines the image characteristics of

a photograph with the geometric qualities of a

map. Standard DOQ’s produced by the USGS are

either grayscale or color-infrared (CIR) images

with a 1-meter ground resolution. The individual

files cover an area that is one-quarter of a standard

1:24,000-scale USGS topographic quadrangle, so

that the resulting data are at a scale of 1:12,000.

Between 50 to 300 meters of overedge are

provided to allow smoother paneling to adjacent

images. Files are formatted either as a standard

USGS DOQ 8-bit binary image or as a GeoTIFF

file. File sizes are typically 50 megabytes for the

grayscale and 150 megabytes for the CIR images.

The USGS also distributes a limited number of

county DOQ data on CD. They consist of individual, Joint Photographic Experts Group (JPEG)

compressed DOQ files that cover select counties.

Applications of DOQ Data

The detail provided by the DOQ allows users 

to evaluate their data for accuracy and completeness, make real-time modifications to their

data, and even generate new files. DOQ data 

can be incorporated into a GIS as a base layer

for displaying, generating, and modifying other

digital data. Additional information about 

DOQ data is available through the Internet at

mapping.usgs.gov/www/ndop/.

A color-infrared digital orthophoto quadrangle of a 

part of the Holder, Florida, 1:12,000-scale quadrangle.
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Digital Line Graph Data

A DLG is a vector representation of the line

information found on USGS topographic maps.

The data are collected as distinct units, and each

unit contains a specific category of data. The

vectors are tagged with attribute codes that 

identify the major category to which the data

element belongs. Additional attribute codes can

be assigned to a data element when more descriptive information is needed. The data are processed

to provide topological structure, which ensures

that the spatial relationships inherent in the

source map are preserved. The data are stored 

in the USGS optional file format.

There are nine units or categories of large-scale

DLG data, which include (1) Public Land 

Survey System (PLSS), including township,

range, and section line information; (2) boundaries, including State, county, city, and other

national and State lands, such as forests and

parks; (3) transportation, including roads and

trails, railroads, pipelines, and transmission 

lines; (4) hydrography, including flowing water,

standing water, and wetlands; (5) hypsography,

including contours and supplementary spot

elevations; (6) nonvegetative features, including

lava, sand, and gravel; (7) survey control and

markers, including horizontal and vertical

positions (third order or better); (8) manmade

features, including cultural features not collected

in other data categories, such as buildings; and

(9) vegetative surface cover, including woods,

scrub, orchards, vineyards, and vegetative 

features associated with wetlands.

Applications of DLG Data

Large-, intermediate-, and small-scale DLG data

are useful in the production of cartographic 

products (for example, base maps). Also, the data

are structured to support GIS technologies. A

typical use of base category digital cartographic

data is to combine them with other geographically

referenced data, thus enabling various automated

spatial analyses. Additional information on DLG

data is available through the Internet at 

edcwww.cr.usgs.gov/nsdi/gendlg.htm.

This graphic shows a part of the Coeur D’Alene, Idaho-Montana,

1:100,000-scale digital line graph. Separate data layers depicting transportation and hydrography have been combined into one data file.
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National Hydrography Dataset

The NHD is a comprehensive set of digital spatial

data that contains information about surface water

features, such as lakes, ponds, streams, rivers,

springs, and wells. Within the NHD, surface 

water features are combined to form “reaches,”

which provide the framework for linking waterrelated data to the NHD surface water drainage

network. These linkages enable the analysis and

display of these water-related data in upstream

and downstream order. 

The NHD is based on the content of USGS DLG

hydrography data integrated with reach-related

information from the Environmental Protection

Agency (EPA) Reach File Version 3 (RF3).

Although initially based on 1:100,000-scale data,

the NHD is designed to incorporate and encourage the development of higher resolution data

required by many users. Complete coverage for 

the United States is expected to be available

sometime early in the year 2000. Delivery 

formats will be available in Arc/Info workspaces and, eventually, in the SDTS format. 

Applications of NHD Data:

The applications of NHD data are similar to those

of DLG hydrography data. Information and data

files for the NHD are available through the

Internet at nhd.usgs.gov/.

This graphic depicts the various levels of hydrologic cataloging 

units as defined by the National Hydrography Dataset.
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National Land Cover Dataset

The NLCD project is part of the interagency

Multiresolution Land Characterization (MRLC)

initiative involving the USGS, the EPA, the National

Oceanic and Atmospheric Administration, and the

U.S. Forest Service. These agencies need a nationally consistent land cover data set, and in 1993 they

combined financial resources to purchase Landsat

thematic mapper data covering the entire United

States. Besides the satellite data, various supplemental information, including topography, census,

agricultural statistics, soil characteristics, other land

cover maps, and wetlands data, is used to determine

and label the land cover type for each 30-meter

pixel. The project delineates 21 classes of land cover

mapped, using consistent procedures for the entire

United States. The data are available on CD in the

GeoTIFF format. 

Applications of NLCD Data:

The NLCD can be used for many different

national and regional applications, including

watershed management, environmental inventories, transportation modeling, fire risk assessment, and land management. Information about

the NLCD is available through the Internet at

edcwww.cr.usgs.gov/programs/lccp/.

The land classifications around Glens Falls, New York, area as 

defined by the National Land Cover Characterization program. 

Each distinct color represents one of 21 classes of land cover.
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Geographic Names

Information System

The GNIS is the Nation’s official automated

geographic names repository. The GNIS was

developed by the USGS in cooperation with the

U.S. Board on Geographic Names (BGN). The

GNIS consists of four separate data bases, each

with unique characteristics and functions. The

National Geographic Names Data Base contains

entries for almost 2 million physical and cultural

geographic features in the United States. The

federally recognized name of each feature in the

data base is identified, and references are made 

to a feature’s location by State, county, and geographic coordinates and to the appropriate

1:24,000-scale USGS topographic map (cell

name) on which it is shown. The Geographic Cell

Names Data Base, formerly the Topographic Map

Names Data Base, contains the official name for

each USGS cell (map series). The Antarctica

Geographic Names Data Base contains names

approved by the BGN for features in Antarctica

and the area extending northward to the Antarctic

Convergence. The Reference Data Base defines

63 broad categories of feature types and describes

their properties. It is also the GNIS information

depository and contains complete annotated 

bibliographies of the source materials used in

compiling the National Geographic Names Data

Base. The National Geographic Names Data Base

and the Antarctica Geographic Names Data Base

are searchable online at mapping.usgs.gov/www/

gnis. The standard GNIS State and territory digital data sets are also available through anonymous ftp at mapping.usgs.gov/www/gnis. The

Digital Gazetteer on CD-ROM contains all four

GNIS data bases.

Applications of the GNIS

The GNIS information has a wide range of

applications. The broad categories of use include

emergency preparedness, local transportation

planning, regional planning, product marketing,

site selection and analysis, genealogical research,

and toponymic problem solving requiring the use

and analysis of geographic names. 

This graphic depicts the various types of names and features that are included 

in the Geographic Names Information System data base.
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Digital Data Formats

In compliance with a Federal mandate to provide

spatial digital data in standardized formats and to

move away from using native formats for spatial

digital products, the USGS uses the SDTS and the

GeoTIFF. The SDTS and GeoTIFF formats are

offered in addition to the native USGS formats

for digital data.

Spatial Data Transfer Standard

The SDTS is a robust way of transferring digital

geospatial data between producers and consumers

who may be using different software and computer systems. The SDTS provides a standard

way to “package” data and information for 

transfer among different GIS platforms. It is 

neutral, modular, growth oriented, extensible, 

and flexible: all characteristics of an open 

systems standard. This transfer standard embraces

the philosophy of self-contained transfers; for

example, spatial data, attributes, georeferencing,

data quality report, data dictionary, and other 

supporting metadata are all included in the 

transfer. These components are all resident in

specified containers or modules that can be 

customized to fit unique data models, such as

raster, vector, and point data. Eventually all

USGS data will be available optionally in the

SDTS format. Additional information about the

SDTS format is available through the Internet at

mcmcweb.er.usgs.gov/sdts/. 

Geographic Tagged-Image File Format

The USGS offers some types of data in a format

called GeoTIFF, a georeferenced version of the

popular TIFF, which allows users with imagerendering programs, Web browsers, image 

processing systems, and GIS’s to easily read 

and display data. 

Additional information on the GeoTIFF 

is available through the Internet at 

www.remotesensing.org/geotiff/faq.html.

Coordinate Systems and Datums

All GeoData are referenced either to the UTM

projection or to a geographic coordinate system.

Some older data are referenced to the North

American datum of 1927 (NAD 27), whereas

newer data are referenced to the NAD 83.

Customers should verify data projections, 

coordinate systems, and datums before ordering

by calling 1-888-ASK USGS or by accessing the

file metadata using the Global Land Information
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USGS GeoData 

Ordering Information

Data can be obtained from these sources:

USGS Business Partners

The USGS has a network of authorized data 

distributors. A list of digital data distributors in

the Business Partner program can be accessed

through the Internet at edcwww.cr.usgs.gov/

buspartners/digital/currentpart.html.

ESIC Network

USGS GeoData can be ordered by contacting the

USGS Earth Science Information Center (ESIC)

network. The ESIC network can be contacted

through the toll-free number 1-888-ASK-USGS

(275-8747). A list of products and services 

available through the ESIC, as well as information on the locations of ESIC offices, can be

accessed at the following Internet address:

mapping.usgs.gov/esic/index.html.

GLIS

USGS GeoData can also be queried for availability and ordered over the Internet by means of the

GLIS at edcwww.cr.usgs.gov/webglis/. GLIS

inventories are reviewed daily to ensure access

to the most current information. The system

operates 24 hours a day, 7 days a week for worldwide connectivity and availability. GLIS will be

replaced by Earth Explorer as a new interface 

to access USGS GeoData sometime in 2000.

Product Status Graphics

The availability of many types of USGS GeoData

can be determined by accessing online status

graphics. The USGS status graphics Web site is

maintained at the following Internet address:

mapping.usgs.gov/www/products/status.html.

GeoData Prices and Media

USGS GeoData are available on CD-ROM and

CD-R, on 8-mm tape, or through ftp. Some types

of data can be downloaded from the World Wide

Web. For more information on prices and delivery

media, contact the ESIC network at 1-888-ASKUSGS or access the following Internet address at

mapping.usgs.gov/mac/isb/pubs/pubslists/

index.html.

Public Domain Software and Sample Data

The USGS maintains an Internet Web site with

access to public domain software for use with

GeoData and other products at the address below:

edcwww.cr.usgs.gov/doc/edchome/ndcdb/

public.html.

Sample data in their native formats are useful for

determining potential applications and compatibility with user software platforms. Sample data

can be assessed at the following address:

edcwww.cr.usgs.gov/doc/edchome/ndcdb/

samples.html.

The USGS also maintains a GeoData Web site

where a wide variety of data types and formats

can be downloaded. These data are available for

assessment purposes and may not be in a format

that can be readily imported into specific operating systems or GIS platforms. The USGS

GeoData Web site can be accessed at the following address: edcwww.cr.usgs.gov/doc/edchome/

ndcdb/ndcdb.html.

For information on other USGS products and

services, call 1-888-ASK-USGS, use the AskUSGS fax-on-demand system, which is available

24 hours a day at 703-648-4888, or visit the 

general interest publications Web site on mapping, geography, and related topics at 

mapping.usgs.gov/mac/isb/pubs/pubslists/

index.html. 

Please visit the USGS home page at 

www.usgs.gov/.