[postgis-users] Problem with transformation (NAD80 to SPCS)

CYW cyw at dls.net
Fri May 26 12:43:38 PDT 2006


Hi all,

I need to project latitude and longitude points in NAD83 to SPCS. The
projection as described in shapefiles prj file is as below:

PROJCS["NAD_1983_StatePlane_Illinois_East_FIPS_1201_Feet",GEOGCS["GCS_North_
American_1983",DATUM["D_North_American_1983"
,SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT[
"Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["F
alse_Easting",984250.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_M
eridian",-88.33333333333333],PARAMETER["Scale_Factor",0.999975],PARAMETER["L
atitude_Of_Origin",36.66666666666666],UNIT["Foot_US",0.3048006096012192]]

This projection is not in the spatial_ref_sys table, the one that is close
to it is SRID 26791, but it is in meter unit. So I creates a projection and
assigned it an SRID 99999.

I tested it with a lat-long data point in NAD83 (SRID=4269), below is the
sql I used:

select AsText(Transform(GeometryFromText('POINT(41.783333 -88.051944)',
4269), 99999));

The response I got, which is wrong, is:
POINT(1531185.06921148 -46594510.0726977)

Obviously, I am wrong somewhere. 

Thanks in advance for any advice.

_CYW_
---------------------------------------------------------------------
Below is the full screen capture showing the projection definition and
transformation sql:
mydb=#   select *  from spatial_ref_sys where  "srid"=99999;
 srid  | auth_name | auth_srid |     srtext   | proj4text


99999 | EPSG      |     99999 |
PROJCS["NAD_1983_StatePlane_Illinois_East_FIPS_1201_Feet",GEOGCS["GCS_North_
American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137.0,2
98.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PR
OJECTION["Transverse_Mercator"],PARAMETER["False_Easting",984250.0],PARAMETE
R["False_Northing",0.0],PARAMETER["Central_Meridian",-88.33333333333333],PAR
AMETER["Scale_Factor",0.999975],PARAMETER["Latitude_Of_Origin",36.6666666666
6666],UNIT["Foot_US",0.3048006096012192]] | +proj=tmerc
+lat_0=36.66666666666666 +lon_0=-88.33333333333333 +k=0.999975 +x_0=300000
+y_0=0 +ellps=GRS80 +units=us-ft +no_defs 
(1 row)

mydb=# select AsText(Transform(GeometryFromText('POINT(41.783333
-88.051944)', 4269), 99999));
                  astext                   
-------------------------------------------
 POINT(1531185.06921148 -46594510.0726977)
(1 row)









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