Frequently Asked Questions
Mapping, Remote Sensing, and Geospatial Data
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No, but additional features in The National Map are found in dynamic services. Expand the Overlays pane above the Content sub-tab, expand individual Base Data Layers by clicking on the + signs, and select which additional features you may want to view at various scales. Symbol legends can be viewed by opening additional content below each ...
Composite base maps have cached tiles to cover the whole world, but only for oceans, continents and countries at smaller scales. Larger view scales have detailed data for the conterminous U.S., Alaska, Hawaii, Puerto Rico, U.S. Virgin Islands, Territory of Guam, Commonwealth of the Northern Mariana Islands, and other Pacific Islands.
Vector data for small scales are from The National Map Small-Scale Collection(formerly National Atlas), while medium to large scales are comprised of The National Map themes, to include the National Hydrography Dataset (NHD) and Geographic Names Information System (GNIS) data. Other medium to large scale vector features are from USGS edited...
USGS does not currently offer vector downloads in bulk other than by special request only. For assistance, send an e-mail to tnm_help@usgs.gov, and include your contact information, requested product, requested area, and download format.
For more information, please follow these links: Demo Examples and TNM Applications.
A list is at The National Map-Service Endpoints.
More Info: How to Use The National Map Services
The Quick Start Guide for The National Map viewer can be found here.
More Info: Tutorial videos
The most recently published figure of absolute vertical accuracy of the seamless DEMs within the conterminous United States, in terms of the National Standard for Spatial Data Accuracy (NSSDA) at 95% confidence level, is 3.04 meters. It is important to note, however, that the vertical accuracy actually varies significantly across the U.S. because...
The laser pulses emitted from airborne lidar systems may be reflected from man-made structures, vegetation, or the earthen surface. A single pulse may reflect from upper, middle, and lower tree canopy as well as the ground beneath, resulting in multiple measurable returns from that pulse. The elevation of the reflected surface(s) is derived based...
The area of coverage of any particular standard 3DEP DEM product is generally determined by the availability of source elevation data of similar or higher resolution. For example, the 1/3 arc-second layer is available for only portions of Alaska where higher resolution lidar or ifsar elevation sources exist. The 1/9 arc-second layer is available...
(Public domain.)
*Contact tnm_help@usgs.gov for current product volume.
All 3DEP seamless DEMs are provided in geographic coordinates (longitude and latitude) in units of decimal degrees, horizontally referenced on the North American Datum of 1983 (NAD83). All elevation values are in units of meters, typically referenced to the North American Vertical Datum of 1988 (NAVD88), although the National Geodetic Vertical...