Why do GeoTIFF images display incorrectly in some GIS applications?
The International Association of Oil & Gas Producers (OGP) Surveying and Positioning Committee maintains and publishes the EPSG Geodetic Parameter Dataset. The OGP recognizes the following codes as valid Indiana EPSG codes used by local and state governments:
The above codes specify the linear unit in feet. Current GeoTIFF specifications use EPSG codes that specify the linear unit in meters:
- 26973 (
- 26974 (
Applications created by vendors such as ERDAS and Esri use two GeoTIFF metadata keys,
ProjLinearUnitsGeoKey, to define Indiana state plane
projections using feet, for example:
ProjectedCSTypeGeoKey: PCS_NAD83_Indiana_East ProjLinearUnitsGeoKey: Linear_Foot_US_Survey
The EPSG code for
PCS_NAD83_Indiana_East is 26973, which
defines the linear unit in meters. This practice violates the GeoTIFF
specifications by overwriting the linear units defined by
ProjectedCSTypeGeoKey with different units defined by the
ProjLinearUnitsGeoKey. Some software applications that
follow a strict interpretation of the GeoTIFF specifications cannot
read the value of the
they display the image using the linear unit of meters. Some reader
software can recognize the problem and apply the appropriate override.
UITS requested that future software versions use the newer
2965 and 2966 EPSG codes as the value for
ProjectedCSTypeGeoKey. ERDAS staff are reviewing this
request and researching other solutions.
Multiple free GIS applications, as well as proprietary applications, are available for viewing geospatial data. If imagery does not display correctly in an application, consider trying a different application.
Additionally, you can modify an image's GeoTIFF metadata tags using
the GDAL utilities'
GDAL_TRANSLATE application to set the GeoTIFF
ProjectedCSTypeGeoKey to 2965 or 2966. The DOS program listgeo will report GeoTIFF
metadata tags to either the screen or to an output text file.
This is document ayiu in the Knowledge Base.
Last modified on 2015-06-03.
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