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72 lines
2.3 KiB
72 lines
2.3 KiB
7 years ago
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shpproj
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using the projection tools proj and invproj
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we have implemented a shapefile projection utility
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shpproj shp_file new_shp ( -i=in_proj_file | -i="in_params" | -i=geographic ) ( -o=out_info_file | -o="out_params" | -o=geographic )
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INPUT
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Input can come from one of three sources. A projection parameter file,
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directly through parameters or geographic. If the shapefile has an associated
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prj file, name the same as the shapefile but ending in ".prj" it will be used
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by default ignoring all other parameters. If input is omitted it defaults to
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geographic, unless the default prj file exists..
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OUTPUT
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Output can come from one of three sources. A projection parameter file,
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directly through parameters or geographic. If output is omitted it defaults
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to geographic.
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PROJECTION PARAMETER FILE
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This file MUST end with the extension ".prj". It has the form of one
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projection parameter per line. Parameters can be in any order.
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PROJECTION PARAMETERS
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Are the same as used by proj and invproj.
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use proj -lP to see available projections
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proj -lu to see available units
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proj -le to see available ellipsoid
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USAGE
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the following example projects file rowtest to row3, moving data from Stateplane NAD83 zone 1002 to utm zone 16 in meters
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shpproj rowtest row -i="init=nad83:1002 units=us-ft" -o="proj=utm zone=16 units=m"
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shpproj rowtest row3 -o="proj=utm zone=18 units=m" -i="zone=16 proj=utm units=us-ft"
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shpproj rowtest row3 -o="proj=utm zone=18 units=m"
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shpproj rowtest row3 -i=myfile.prj -o=geographic
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shpproj rowtest row3 -is=myfile.prj
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Datums
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Stateplane data can be accessed by the init function
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init=nad83:1003
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which is of the form
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datum:FIPSzone
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To move from NAD27 to NAD83 or otherwise the shpproj utility moves to
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geographic coordinates and the back to the desired datum. proj can handle
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direct datum to datum conversions but it is umimplemented here.
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for a complete listing of FIPSZones by datum read nad/nad.lst in the PROJ4
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library
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CAUTION
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It is possible to get very poor results for projection values when using
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coordinates VERY far away from the intended scope of the projection.
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An example of a poor projection choice would be to move from nad83:1002
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(Georgia West) for data in California into utm. The resulting data will be
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much less accurate than if it had started as geographic.
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