Am 05.09.2017 um 16:56 schrieb Even Rouault:
The problem is that there is no EPSG code for the projection,
Ah, the -s_srs syntax is not limited to EPSG:XXXX. You can use a proj.4 string,
inlined WKT, a
filename that has WKT or proj.4 string in it, etc.
See http://gdal.org/gdal_utilities.html
and NAD27
datum is handled badly outside the US and Canada. The country in
question is El Salvador, where they adopted NAD27, but it's not part of
the NAD27 datum shift files. EPSG suggests a Ocotepeque datum, which is
shifted to NAD27.
Isn'it the datum used by ?
$ gdalsrsinfo EPSG:5451
PROJ.4 : +proj=longlat +ellps=clrk66 +towgs84=205,96,-98,0,0,0,0 +no_defs
OGC WKT :
GEOGCS["Ocotepeque 1935",
DATUM["Ocotepeque_1935",
SPHEROID["Clarke 1866",6378206.4,294.9786982138982,
AUTHORITY["EPSG","7008"]],
TOWGS84[205,96,-98,0,0,0,0],
AUTHORITY["EPSG","1070"]],
PRIMEM["Greenwich",0,
AUTHORITY["EPSG","8901"]],
UNIT["degree",0.0174532925199433,
AUTHORITY["EPSG","9122"]],
AUTHORITY["EPSG","5451"]]
The TOWGS84 parameters are the ones of transformation http://epsg.io/6891 that
is valid
for El Savador (and neighbouring countries). There are other transformations
from
Octopeque 35 to WGS 84, but none have an area of use that include El Savador.
They are also transformations from Octopeque 35 to NAD 27.
The shapefile clearly states DATUM["D_North_American_1927", and the
download page (from the official agency)
http://www.cnr.gob.sv/geoportal-cnr/ tells the same.
In fact, I have not found any Ocotepeque based GIS data available from
El Salvador, only from the surrounding countries.
Greetings,
André Joost
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