GISRSStudy » Remote Sensing » Digital Elevation Model

Digital Elevation Model (DEM)

A Digital Elevation Model (DEM) is a represent ground/Earth Surface Topography or Terrain. It is also widely known as a Digital Terrain Model (DTM). DEMs are commonly built using Remote Sensing techniques, and also used often in GIS.

Digital Elevation Model-DEM data
DEM Data

A DEM data are stored in ASCII format. The data file values in ASCII format are stored as ASCII characters rather than as zeros and ones like the data file values in binary data.

DEM File Formats:

Types of DEM

Digital terrain data covering most regions in the United States is available in the USGS DEM format from the U.S. Geological Survey.

There are two types of historic DEMs that are most commonly available from USGS:

  1. 7.5-minute DEM
  2. 1-degree DEM

Both types have a 16-bit range of elevation values, each pixel can have a possible elevation of -32,768 to 32,767.

Factor7.5-minute DEM1-degree DEM
Geographic extent
in latitude and longitude7.5′ x 7.5′1° x 1°
in kilometers (approx.)12 km x 14 km90 km x 110 km
Zone1 to 60N/A
Ground Unitsmetersarc seconds
Surface Z Unitsmetersmeters
SpheroidClarke 1866WGS72
Distance between elevation points in x and y30 meters x 30 meters3 arc seconds 75 meters x 75 meters (approx. in the United States)
Number of elevation points in x and yVaries. The typical column counts range from 345 to 385, and row counts from 460 to 475.Constant of 1201 x 1201.
Variation in ground distance between elevation point spacing across the raster datasetNo variation; the spacing is constant.Varies with the latitude.

Create DEM from Google Earth

Follow this Tutorial, How to Create DEM from Google Earth.

Download DEM Data

Many Sources are available for Download Free DEM Data files.

Methods for Obtaining DEM

There are many different methods for gathering digital elevation data

  • Stereo Photogrammetry
  • Multi-view stereo applied to aerial photography
  • Theodolite or total station
  • Real Time Kinematic GPS
  • Topographic maps
  • Inertial surveys
  • Focus variation
  • Doppler radar

Uses of Digital Elevation Model

Common uses of DEMs include:

Leave a Comment

Your email address will not be published. Required fields are marked *

Tutorial Contents
Scroll to Top