Hello,<div><br></div><div>I have a Trimble Ag252 GPS [0] and an OmniStar HP subscription for corrections [1] for our robotics project [2]. According to that link [1], OmniStar uses ITRF2005, which I'm having trouble getting to work on python-gdal in Ubuntu 10.10.</div>
<div><br></div><div>I'm converting the lat / long pair we get from the GPS device into UTM easting / northing so we can localize our robot and compare our current position from the starting position by simply using addition / subtraction / the pythagorean theorem. I'm using code similar to the following to convert (slightly simplified):</div>
<div><br></div><div>-------------- snip -------------------</div><div><div>ellipsoid = "WGS84" # or could be EPSG:4919 etc</div><div><br></div><div>utm = osgeo.osr.SpatialReference()</div><div>utm.SetWellKnownGeogCS(ellipsoid)</div>
<div>ll = osgeo.osr.SpatialReference()</div><div>ll.SetWellKnownGeogCS(ellipsoid)</div><div><br></div><div>zone = int(math.floor((lon + 180.0) / 6.0) + 1.0)</div><div>utm.SetProjCS("UTM %d / %s" % (zone, ellipsoid))</div>
<div>utm.SetUTM(zone)</div><div>trans = osgeo.osr.CoordinateTransformation(ll, utm)</div><div><br></div><div>trans.TransformPoint(lat, lon, 0.0)</div></div><div><br></div><div><meta http-equiv="content-type" content="text/html; charset=utf-8">-------------- snip -------------------</div>
<div><br></div><div>When I grep inside /usr/share/gdal16/, I can find some references to ITRF but no definition.</div><div><br></div><div>When I look up ITRF on <a href="http://spatialreference.org">spatialreference.org</a>, I find EPSG numbers 4385 [3] and 4919[4] for ITRF2000 but I get this error: "ERROR 6: EPSG PCS/GCS code 4919 not found in EPSG support files. Is this a valid EPSG coordinate system?" Same with 4896 for ITRF2005.</div>
<div><br></div><div>When I grep inside /usr/share/gdal16/ for ITRS, I find "6896,International Terrestrial Reference Frame 2005,geodetic," in gdal_datum.csv. This seems to be what I'm looking for, but I have no clue how to use it. How would I go about doing this?</div>
<div><br></div><div>I've also read that "new realizations of WGS84" are at about 10cm from ITRF [5], but is the WGS84 that GDAL uses one of the ones referred to in that document? Also, it doesn't specify which ITRF looks like ITRF90, which is old. Even though I could fall back to using WGS84, I'd prefer not to since it seems that it'd defeat the purpose of using a +-10cm corrections service, and I don't know if our application could tolerate much more than +-50cm.</div>
<div><br></div><div>We are, however, generating a *local* map that's based on the origin position we start the robot at, so coordinates that were *uniformly* shifted over would not be a problem. Is that the case with regards to ITRF2005 vs WGS84?</div>
<div><br></div><div>Thanks,</div><div>-- <br>~ mali (<a href="http://constant.inople.net/">http://constant.inople.net/</a>)<br>
</div><div><br></div><div><meta http-equiv="content-type" content="text/html; charset=utf-8"><div>[0] <a href="http://trl.trimble.com/dscgi/ds.py/Get/File-159152/AgGPS252_100A_UserGuide_55510-00-ENG.pdf">http://trl.trimble.com/dscgi/ds.py/Get/File-159152/AgGPS252_100A_UserGuide_55510-00-ENG.pdf</a></div>
<div>[1] <a href="http://www.omnistar.com/faq.html#accuracy">http://www.omnistar.com/faq.html#accuracy</a></div><div>[2] <a href="http://www.igvc-wpi.org/">http://www.igvc-wpi.org/</a></div><div>[3] <a href="http://spatialreference.org/ref/epsg/4385/">http://spatialreference.org/ref/epsg/4385/</a></div>
<div>[4] <a href="http://spatialreference.org/ref/epsg/4919/">http://spatialreference.org/ref/epsg/4919/</a></div><div>[5] <a href="ftp://itrf.ensg.ign.fr/pub/itrf/WGS84.TXT">ftp://itrf.ensg.ign.fr/pub/itrf/WGS84.TXT</a></div>
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