<div dir="ltr">Thanks for the suggestion, Nicholas.<div><br><div>I do have the latest NTv2 gsb file (13.5MB!).</div><div><br><div>Unfortunately, I require an offline solution - internet &/or cell data connections will often be unavailable. </div><div>For that matter, relying on the continued existence of 'governement funded' tools might also be a concern.</div><div>Canada is not immune to arbitrary swings of the economic axe. Or they might just move the tool to some other URL.</div><div>Either way would bork my app.</div><div>;-)</div><div><br></div><div><br></div></div></div></div><br><div class="gmail_quote"><div dir="ltr">On Tue, Nov 13, 2018 at 4:02 PM Nicolas Cadieux <<a href="mailto:nicolas.cadieux@archeotec.ca">nicolas.cadieux@archeotec.ca</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto"><div></div><div>Hi,</div><div>Comments below..</div><div><br>Le 13 nov. 2018 à 15:03, Robb Main <<a href="mailto:rmain.mws@gmail.com" target="_blank">rmain.mws@gmail.com</a>> a écrit :<br><br></div><blockquote type="cite"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr">I need to convert WGS84 (lat, long) coordinates from GPS to NAD27 UTM Eastings & Northings coordinates, primarily in Canada, in an Android environment. To maximize accuracy of the end result, I believe the NTv2 grid corrections must be applied (though adding 13.5MB to the final solution is not desireable).</div></div></div></div></div></blockquote><div><br></div>Yes this is correct. The first step will be to go from WGS84 transit to <span style="background-color:rgba(255,255,255,0)">NAD83(CSRS) and then to NAD27 using the grid files. </span>Make sure you have the last version of the grid from <div><div><a href="https://open.canada.ca/en/suggested-datasets/ntv2-grid-shift-files-gsb" target="_blank">https://open.canada.ca/en/suggested-datasets/ntv2-grid-shift-files-gsb</a>.</div><div><br></div><div>Perhaps the easiest way is to link the android tool to the nrcan web tools? It depends on the availability of wifi or cell coverage.</div><div><br></div><div><a href="http://webappd.geod.nrcan.gc.ca/geod/tools-outils/trx.php?locale=fr&wbdisable=true" target="_blank">http://webappd.geod.nrcan.gc.ca/geod/tools-outils/trx.php?locale=fr&wbdisable=true</a></div><div><div><div><br></div><div><a href="http://webapp.geod.nrcan.gc.ca/geod/tools-outils/ntv2.php" target="_blank">http://webapp.geod.nrcan.gc.ca/geod/tools-outils/ntv2.php</a></div><div><br></div><div>Good luck</div><div><br><blockquote type="cite"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div><br></div><div>I've looked at Proj.4 codebase, and I'm not at all sure it's the best tool for this purpose. The JNI support for proj.4 appears to be for java support under linux/windows/macos. GDAL uses proj.4 & appears to build for android ( <a href="https://trac.osgeo.org/gdal/wiki/BuildingForAndroid" target="_blank">https://trac.osgeo.org/gdal/wiki/BuildingForAndroid</a> ), so it _IS_ possible (with some pain), though I'm not sure this is current info. Regardless, GDAL is overkill for my needs, as all I need is coordinates. </div><div><br></div><div>I also found the proj4j library (a java port of the proj4 code - <a href="http://svn.osgeo.org/metacrs/proj4j/trunk/src/README.html" target="_blank">http://svn.osgeo.org/metacrs/proj4j/trunk/src/README.html</a>), though it looks like it was last updated 5 years ago, and its not clear if grid support was ever fully implemented / operational.</div><div><br></div><div>I found CTS ( <a href="https://github.com/orbisgis/cts" target="_blank">https://github.com/orbisgis/cts</a> ), which is a straight JAVA library, implementing the required tranformations & supporting grids, but there is little information / no examples on its use. Since it is pure java, I expect it would be easier to implement in an android build environment.</div><div><br></div><div>Please comment on the above if you have experience with them, or point me in the right direction if you have some other suggestion.</div><div><br></div><div>Thank you.</div><div><br></div><div><br></div></div></div></div></div>
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