<div dir="ltr">The epsg file included with proj has definitions for hpgn coordinate systems that do not use the grid shift files, for example:<div><div># NAD83(HARN) / Wyoming West (ftUS)</div><div><3758> +proj=tmerc +lat_0=40.5 +lon_0=-110.0833333333333 +k=0.9999375 +x_0=800000 +y_0=100000 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=us-ft +no_defs <></div><div><br></div><div>So there is no datum transformation applied. But proj has the appropriate harn grid shift files here:</div><div><a href="http://trac.osgeo.org/proj/wiki/HarnGrids">http://trac.osgeo.org/proj/wiki/HarnGrids</a></div><div><br clear="all"><div>And changing the above definition to include the grid shift files like below seems more appropriate:</div><div><div># NAD83(HARN) / Wyoming West (ftUS)</div><div><3758> +proj=tmerc +lat_0=40.5 +lon_0=-110.0833333333333 +k=0.9999375 +x_0=800000 +y_0=100000 +ellps=GRS80 +nadgrids=wyhpgn.gsb +units=us-ft +no_defs <></div></div><div><br></div><div>Does the proj epsg file get created from data at <a href="http://www.epsg.org">www.epsg.org</a>? And is that data lacking the reference to the grid shift files, or is it "lost in translation"? It seems like there is the wonderful resource in the harn grids that isn't getting used, but maybe I'm overlooking something.</div><div><br></div><div>Rich</div><div><br></div>-- <br><div class="gmail_signature"><div dir="ltr">Richard W. Greenwood, PLS<br><a href="http://www.greenwoodmap.com" target="_blank">www.greenwoodmap.com</a></div></div>
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