Introduction to Data

Data formats supported

Optimal usage in the US uses support data, placed in the correct directories.

When downloading and setting up additional data, you should understand the concept of local map databases, for TIGER data, and the map library.  For standard data sets, if you keep the files in the compressed format from the web site, MICRODEM will automatically unzip them when required and then delete the expanded files when you close the program. You also do not have to worry about file names; you can keep the cryptic names from the government mapping agencies, and let the computer keep track of file names and locations, and merge data sets as required. You are strongly encouraged to use the database function to let the computer help you organize your data.

For the purposes of this program and its documentation, a Digital Elevation Model (DEM) includes any gridded digital data that can be displayed as if it were a DEM. Examples include topography, bathymetry, gravity and magnetic anomalies.  A satellite image includes any image  that can be manipulated as if it were a satellite image. Examples include side scan sonar, slide looking airborne radar, orthophotography, or scanned maps.  Internally the program considers imagery and scanned maps to be identical.   Vector data consists of line segments.

This program uses essentially all the map data provided by the major US Government mapping agencies, USGS (United States Geological Survey) and NGA (National Geospatial-Intelligence Agency, formerly National Imagery and Mapping Agency, formerly Defense Mapping Agency), as well as data from NASA, NOAA, and the Census Bureau.  Much of the NGA data will only be available to US military users, but a surprising amount of NGA data world wide can be downloaded free.  The program also displays the most common interchange formats for digital mapping data, Shapefiles and Geotiff.   This bias on US data reflects two facts of life:

  1. This is the data I use because of where I live.
  2. US data is largely free, in striking contrast to most of the rest of the world where digital map data is not a public domain product created by the government.

The program comes with a limited amount of data, a 1:24K USGS DEM for Hanging Rock Canyon, California,  and several geological data bases. 

Additional data files available. 

Last revised 2/22/2015