<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<style type="text/css" style="display:none;"> P {margin-top:0;margin-bottom:0;} </style>
</head>
<body dir="ltr">
<div style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);" class="elementToProof">
Mladen,</div>
<div style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);" class="elementToProof">
See this thread where Even suggests how to use arbitrary grid shift in WKT CRS definition.</div>
<div style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);" class="elementToProof ContentPasted0">
<a href="https://lists.osgeo.org/pipermail/proj/2019-December/009143.html" id="LPlnk806954" class="OWAAutoLink">https://lists.osgeo.org/pipermail/proj/2019-December/009143.html</a><br>
</div>
<div style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);" class="elementToProof ContentPasted0">
<br>
</div>
<div style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);" class="elementToProof ContentPasted0 ContentPasted1">
You would need to use ABRIDGEDTRANSFORMATION. <a href="https://docs.ogc.org/is/18-010r7/18-010r7.html#151" id="LPlnk453100">https://docs.ogc.org/is/18-010r7/18-010r7.html#151</a></div>
<div style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);" class="elementToProof ContentPasted0 ContentPasted1">
<br>
</div>
<div style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);" class="elementToProof ContentPasted0 ContentPasted1">
Sincerely, Erixen</div>
<div id="appendonsend"></div>
<hr style="display:inline-block;width:98%" tabindex="-1">
<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> PROJ <proj-bounces@lists.osgeo.org> on behalf of Mladen Mijatovic via PROJ <proj@lists.osgeo.org><br>
<b>Sent:</b> Monday, September 25, 2023 5:56 AM<br>
<b>To:</b> proj@lists.osgeo.org <proj@lists.osgeo.org><br>
<b>Subject:</b> [PROJ] Gridshift files</font>
<div> </div>
</div>
<div>
<div dir="ltr">Dear,<br>
<br>
We are trying to substitute old Proj 5.1 in our project and use new Proj<br>
9.2.1.<br>
<br>
When crs is defind with proj4string or wkt, we do not have issue with<br>
transforming coordinates from/to EPSG:4326, except when we are using<br>
grid files e.g.<br>
<br>
+proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000<br>
+datum=OSGB36 +units=m +ellps=airy +no_defs<br>
+nadgrids=OSTN15_NTv2_OSGBtoETRS.gsb +type=crs<br>
<br>
PROJCS["ED50 / 3-degree Gauss-Kruger zone 10",<br>
GEOGCS["ED50",<br>
DATUM["European_Datum_1950",<br>
SPHEROID["International 1924",6378388,297],<br>
EXTENSION["PROJ4_GRIDS","SPED2ETV2.gsb"]],<br>
PRIMEM["Greenwich",0,<br>
AUTHORITY["EPSG","8901"]],<br>
UNIT["degree",0.0174532925199433,<br>
AUTHORITY["EPSG","9122"]],<br>
AUTHORITY["EPSG","4230"]],<br>
PROJECTION["Transverse_Mercator"],<br>
PARAMETER["latitude_of_origin",0],<br>
PARAMETER["central_meridian",30],<br>
PARAMETER["scale_factor",1],<br>
PARAMETER["false_easting",10500000],<br>
PARAMETER["false_northing",0],<br>
UNIT["metre",1,<br>
AUTHORITY["EPSG","9001"]],<br>
AUTHORITY["EPSG","2207"]]<br>
<br>
Conversion fails with (HUGE_VAL, HUGE_VAL) coordinates.<br>
<br>
If we allow user to define crs by proj4string or wkt and use gridshift<br>
files:<br>
<br>
- How proj4string/wkt need to looks like?<br>
<br>
- What c++ functions we need to call to get these coordinates converted<br>
without any errors?<br>
<br>
<div>Best regards,</div>
<div>Mladen.<br>
</div>
</div>
</div>
</body>
</html>