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--- technologies:crs:prj [2014/05/13 07:41]
jeroen.vermeulen@orbitgis.com
+++ — (current)
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-<html>
-<div align="right">
-</html>Back to [[technologies:resources:supported_formats|]] \\ Back to [[technologies:crs:crs_orbit|]]
-<html>
-</div>
-</html>
-====== Projection Definition File ======
-| Name | Projection Definition File |
-| Acronym | PRJ |
-| File Extension | *.prj |
-The prj-file is a plain text file describing the the coordinate system and projection information using text format. \\ \\
-A prj-file can be used to define a custom Orbit Coordinate system, which can be used to define the dataset crs : [[technologies:crs:crs_orbit|]] \\
-The prj-file cannot be used as direct dataset coordinate definition. A dataset coordinate definition in Orbit is saved in the [[technologies:basic_concepts:ord|Orbit Resource Description]] file.
-<note important>The name of the file should be a numeric code, like "1031370.prj" for example.
-This numeric code should be larger than 1000000 (one million) to avoid overlap with existing EPSG codes.
-An optional description can be added to the filename if an underscore character follows the numeric code, like "1031370_Belge 1972 - Belgian Lambert 72.prj" for example.</note>
-===== Information in PRJ file =====
-Some typical information contained in the .prj file is:
-  * Geographic coordinate system
-  * Datum
-  * Spheroid
-  * Prime meridian
-  * Map projection
-      * Latitude of origin
-      * Scale factor
-      * Central meridian
-      * False northing
-      * False easting
-      * Standard parallels
-  * Units used
-===== PRJ Features =====
-==== Format ====
-The text is created in the [[http://http://www.opengeospatial.org/docs/01-009.pdf | WKT-format]]: Support of WKT is under development. Not all features are fully supported (like vertical coordinate systems or special units).
-Feel free to send an email to support@orbitgis.com if your WKT file is not working as expected. \\
-Do not forget to add the "TOWGS84" element (with seven parameters) to the "DATUM" element. See section "7.3.18 TOWGS84" of the WKT specification.
-<note>the units for the seven parameters are as follows: (meter,meter,meter, arc-sec,arc-sec,arc-sec, parts-per-million). The signs of the angles should be as the EPSG "Position Vector 7-parameter transformation" method (code 9606), not the "Coordinate Frame Rotation" method (code 9607). See "EPSG Guidance Note 7, Part 2" at: http://info.ogp.org.uk/geodesy/guides/docs/G7-2.pdf</note>
-==== Example ====
-<code html>
-PROJCS["NAD83 / Austin", \
-  GEOGCS["NAD83", \
-    DATUM["North_American_Datum_1983", \
-      SPHEROID["GRS 1980", 6378137.0, 298.257222101], \
-      TOWGS84[0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]], \
-    PRIMEM["Greenwich", 0.0], \
-    UNIT["degree", 0.017453292519943295], \
-    AXIS["Lon", EAST], \
-    AXIS["Lat", NORTH]], \
-  PROJECTION["Lambert_Conformal_Conic_2SP"], \
-  PARAMETER["central_meridian", -100.333333333333], \
-  PARAMETER["latitude_of_origin", 29.6666666666667], \
-  PARAMETER["standard_parallel_1", 31.883333333333297], \
-  PARAMETER["false_easting", 2296583.333333], \
-  PARAMETER["false_northing", 9842500.0], \
-  PARAMETER["standard_parallel_2", 30.1166666666667], \
-  UNIT["m", 1.0], \
-  AXIS["x", EAST], \
-  AXIS["y", NORTH], \
-  AUTHORITY["EPSG","100002"]]
-</code>
-<note important>The text is inserted on a single line or with backslash characters
-</note>
-==== Supported Projection Methods ====
-^  [[http://www.epsg-registry.org/|EPSG]] ^ Projection Name ^
-|  9812  | Hotine_Oblique_Mercator |
-|  9819  | Krovak |
-|  9801  | Lambert_Conformal_Conic_1SP |
-|  9802  | Lambert_Conformal_Conic_2SP |
-|  9803  | Lambert_Conformal_Conic_2SP_Belgium |
-|  9802  | Lambert_Conformal_Conic |
-|  9804  | Mercator_1SP |
-|  9815  | Oblique_Mercator |
-|  9809  | Oblique_Stereographic |
-|  9807  | Transverse_Mercator |
-\\
-===== Why use PRJ-files =====
-A lot of pre-defined Coordinate Reference Systems and Coordinate Transformations are accessible through the Orbit Software by using the EPSG Geodetic Parameter Dataset. However, the EPSG database does not record all possible geodetic parameters in use around the world. In addition to the pre-defined CRS in the EPSG database, OrbitGIS accepts custom CRS definitions by creating seperate PRJ-files.

Last modified:: 2014/05/13 07:41