Problem importing shape files projected in Texas State Plane SC Zone NAD 27

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02-16-2012 05:37 AM
JeromyChandler
New Contributor
We have shape files with a .prj of

PROJCS["NAD27_Texas_South_Central_ft",GEOGCS["GCS_Geographic Coordinate System",DATUM["D_NORTH_AMERICAN_1927",SPHEROID["Clarke_1866",6378206.4,294.9786982]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Lambert_Conformal_Conic"],PARAMETER["scale_factor",1],PARAMETER["standard_parallel_1",28.38333333333333],PARAMETER["standard_parallel_2",30.28333333333334],PARAMETER["central_meridian",-99],PARAMETER["latitude_of_origin",27.83333333333333],PARAMETER["false_easting",1999999.999998562],PARAMETER["false_northing",0],UNIT["Foot_US",0.30480060960121924]]

When this shape file is imported into ArcGIS set to GCS_North_American_1927 there is about a 100 foot shift.
If I take the same shape file and re project it to NAD 83 from 27 with this .prj

PROJCS["NAD83_Texas_South_Central_ft",GEOGCS["GCS_Geographic Coordinate System",DATUM["D_NORTH_AMERICAN_1983",SPHEROID["GRS_1980",6378137,298.257222101]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Lambert_Conformal_Conic"],PARAMETER["scale_factor",1],PARAMETER["standard_parallel_1",28.38333333333333],PARAMETER["standard_parallel_2",30.28333333333334],PARAMETER["central_meridian",-99],PARAMETER["latitude_of_origin",27.83333333333333],PARAMETER["false_easting",1968500],PARAMETER["false_northing",13123333.33333333],UNIT["Foot_US",0.30480060960121924]]

It imports into ArcGIS set to GCS_North_American_1927 just fine.

Any ideas of why this is happening?
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MelitaKennedy
Esri Notable Contributor
This GCS definition doesn't match the ArcGIS version of NAD27, so there are no valid transformations to convert it to NAD83 or WGS84, etc.

GEOGCS["GCS_Geographic Coordinate System",DATUM["D_NORTH_AMERICAN_1927",SPHEROID["Clarke_1866",6378206.4,294.9786982]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]]

Esri's version looks like this:

GEOGCS["GCS_North_American_1927",DATUM["D_North_American_1927",SPHEROID["Clarke_1866",6378206.4,294.9786982]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433],AUTHORITY["EPSG",4267]]

The capitalization of the DATUM name nor the Degree value matter, but the GCS name must match as well. You could use the Define Projection tool or the data's property page in ArcCatalog to set the coordinate system to the ArcGIS version.

Melita
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