postgis - ESRI projection to SRID?

I am looking at MapX and MapY coordinates. The docs say they are "truncated State Plane coordinates: NAD 1983 State Plane Louisiana South FIPS 1702 (US Feet)."

I am trying to reproject into a common lat/long like wgs-84 by using PostGIS so I need the srid for this projection.

I found the spatial reference page for the state plane coordinates http://spatialreference.org/ref/esri/102682/ -- but it does not list the SRID.

I found this page of common SRIDs -- but if I plug in the SRID the projection does not output correct lat/longs.

How can I find an authoritative SRID?

Answer

The proj definition for EPSG:102682 is

+proj=lcc +lat_1=29.3 +lat_2=30.7 +lat_0=28.5 +lon_0=-91.33333333333333 +x_0=1000000 +y_0=0 +datum=NAD83 +units=us-ft +no_defs

and for EPSG:3452 it is

+proj=lcc +lat_1=30.7 +lat_2=29.3 +lat_0=28.5 +lon_0=-91.33333333333333 +x_0=999999.9999898402 +y_0=0 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=us-ft +no_defs

So lat_1 and lat_2 are swapped (which makes no difference) and x_0 is off by less than one millimeter.

I don't see any reason not to call them identical.

For official EPSG projections, the SRID in postgis is identical with the EPSG code. But 102682 is from ESRI, that's why you will not find it in the official EPSG database. PROJ/GDAL/QGIS call it EPSG:102682, but it should rather be ESRI:102682 (as spatialreference.org calls it).