<div dir="ltr"><div><div><div>use<br> +init=blabla +inv<br><br></div>For cct, there's also the -I switch:<br><br></div> cct -I +init=blabla<br><br></div>/Thomas<br></div><div class="gmail_extra"><br><div class="gmail_quote">2018-02-21 22:18 GMT+01:00 stevejking <span dir="ltr"><<a href="mailto:stevejking@talktalk.net" target="_blank">stevejking@talktalk.net</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Is it possible to use a +init pipeline file in reverse?<br>
<br>
For example, with some explanation from Kristian, I now have two<br>
transformations:<br>
<br>
# OSGB1936 to ETRS89(2)<br>
<7709-3D> -t0 +proj=pipeline \<br>
+step +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717<br>
+x_0=400000 +y_0=-100000 +ellps=airy +inv \<br>
+step +proj=vgridshift<br>
+grids=OSGM15_GTX_OSGBtoGRS80.<wbr>gtx +inv \<br>
+step +proj=hgridshift<br>
+grids=OSTN15_NTv2_OSGBtoETRS.<wbr>gsb<br>
<br>
# ETRS89 to OSGB1936<br>
<7709-3D-Reverse> -t0 +proj=pipeline \<br>
+step +proj=hgridshift<br>
+grids=OSTN15_NTv2_OSGBtoETRS.<wbr>gsb +inv \<br>
+step +proj=vgridshift<br>
+grids=OSGM15_GTX_OSGBtoGRS80.<wbr>gtx \<br>
+step +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717<br>
+x_0=400000 +y_0=-100000 +ellps=airy<br>
<br>
<br>
The only difference between the two is the reverse order and swapping the<br>
+inv and 'no inv blanks' on the end of each line. I'm wondering if I need<br>
two separate transformations?<br>
<br>
If not is it a sensible future development? +init=<...> +reverse ?<br>
<br>
Steve<br>
<br>
<br>
<br>
--<br>
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</blockquote></div><br></div>