Geospatial Data Formats
Geospatial data is created, shared, and stored in many different formats. The following list is not intended to be comprehensive, but only provides information on formats common in NCSU Libraries' geospatial data collection. For information about additional formats, see
- GISDataDepot Format Listing and Discussion
- Wikipedia: GIS_file_formats
- Very comprehensive format listing from Grime.net
Vector Data File Formats
SDC: Smart Data Compression
SDC is ESRI's highly compressed format, which is directly readable by ArcGIS software, but not by ArcView 3.x. Many ESRI Data and Maps datasets are natively in SDC format.
With ESRI Data and Maps 2006, a standalone "Data Distribution Application" was included that converts SDC data files directly to shapefiles. This application may be downloaded from the Geodata Server at http://gisdata.lib.ncsu.edu/esri2006/data_maps/DDA/ or off-campus from here. A help file is also included at this download location.
LYR: Layer File
A .lyr file is directly readable only by ArcGIS software and other newer software applications. This file does not contain actual geographic data, but rather contains specifications for the presentation of other datasets. Such specifications include color shading, naming, label properties (font, color, placements, etc.). Such presentation properties are usually time consuming to create, so a .lyr file allows these settings to be saved and shared. In order to use a .lyr file, you must also have a seperate data file with the same prefix name saved in the same filespace.
The ESRI Shapefile has become an industry standard geospatial data format, and is compatible to some extent with practically all recently released GIS software.
To have a complete shapefile, you must have at least 3 files with the same prefix name and with the following extensions: .shp = shapefile, .shx = header and .dbf = associated database file. Additionally, you may have a .prj = Projection file, a .lyr = layer file, and other index files. All these files must be saved in the same workspace.
An ArcInfo coverage does not have an individual file extension. Instead it is composed of two folders within a "workspace" which each contain multiple files. One of the two folders carries the name of the coverage, and contains a number of various .adf files. The other folder is an "info" folder, which typically contains .dat and .nit files for all the coverages and grids in the workspace. The best way to manage (copy, move, delete, rename) ArcInfo coverages is with ArcCatalog or ArcInfo Workstation (command line).
E00: Arc Export or Interchange Format
.e00 (pronounced e-o-o or e-zero-zero) files are ArcInfo Interchange or export files, used to conveniently copy and move ArcInfo GIS coverages (see above) and grids (see below). An .e00 file must be "imported" in order to use the data in ArcView or other GIS software.
If you are using ArcGIS 9.1, use the "Import from Interchange File" tool to import the e00 to an ArcInfo coverage. This tool is in ArcToolbox->Coverage Tools->Conversion->To Coverage. Go to this FAQ page from the State of Washington for detailed instructions on importing an .e00 file with ArcToolbox.
If you have ArcView 3.x installed, use the Import71 utility found on the Start Menu along with ArcView to import the .e00 file. If you are running ArcView from Novel Application Launcher (NAL), you will need to locate the ArcView path (probably on the L: drive) by right-clicking on the NAL ArcView icon and looking at 'Properties'. Look for import71.exe under the ArcView /bin32 directory and click on it to run the program.
If you don't have ArcView 3.x or 8.x, download the free ArcExplorer Import Utility from ESRI.
ArcInfo Workstation users may use the Import command.
The geodatabase is a collection of geographic datasets of various types, with the most basic types being vector, raster, and tabular data. There are three types of geodatabases: file, personal, and ArcSDE. Geodatabases are the native data format for ESRI's ArcGIS. A full discussion and online help is available at ESRI Support Center.
TIN: Triangular Irregular Network
A TIN is a vector-based model which represents geographic surfaces as contiguous non-overlapping triangles. The vertices of each triangle are known data points (x,y) with values in the third dimension (z) taken from surveys, topographic maps, or digital elevations models (DEMs). The surface of each triangle has a slope, aspect, surface area, and continuous, interpolated elevation values. The selective inclusion of points within a TIN gives the triangles their irregular pattern and reduces the amount of data storage required relative to the regularly distributed points in a DEM.
Raster Data File Formats
An ArcInfo Grid does not have an individual file extension. Instead it is composed of two folders within a "workspace" which each contain multiple files. One of the two folders carries the name of the grid, and contains a number of various .adf files. The other folder is an "info" folder, which typically contains .dat and .nit files for all the coverages and grids in the workspace. The best way to manage (copy, move, delete, rename) ArcInfo Grids is with ArcCatalog or ArcInfo Workstation (command line).
MrSID (pronounced "mister sid") is a proprietary format of LizardTech's GeoExpress software for imagery compression, and is commonly used on orthoimages. See the DOQQ page for MrSID content. The MrSID file extension is .sid. A companion file with a .sdw extension and the same prefix name as the .sid is used as a world file for georeferencing a MrSID image.
Most greyscale TIFF images are compressed with MrSID to 10:1 or 15:1. Color images are usually compressed to 30:1 or 40:1. GeoExpress is also commonly used to create image mosaics.
Most recent GIS software, including ArcGIS, are able to read MrSID compressed images without any additional extensions. ArcView 3.x, however, requires a MrSID Extension for image access. Plugins for other software, such as AutoCAD and Photoshop, may or may not be required.
ECW is a proprietary format of ERMapper for imagery compression. It is a more recent format than MrSID, but is gaining popularity because of free compression utilities available from ER Mapper's website.
JPEG 2000 is a non-proprietary image compression format based on ISO standards, and typically uses .jp2 as the file extension. It's advantages are that it offers lossy and lossless compression, and world files (.j2w) can be used to georeference an image in GIS software. Compression ratios are similar to MrSID and ECW formats. For more information, see the Wikipedia entry for JPEG 2000.