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<div class="">Hi,</div>
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<div class="">Trying to answer with my knowledge :</div>
<div class="">On my computer I can do this transform in this way</div>
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<span style="font-variant-ligatures: no-common-ligatures" class="">echo -6.6 53 21 | cs2cs +init=epsg:4326 +to +proj=tmerc +lat_0=53.5 +lon_0=-8 +k=0.99982 +x_0=600000 +y_0=750000 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +geoidgrids=egm08_25_rg.gtx +units=m +no_defs</span></div>
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<span style="font-variant-ligatures: no-common-ligatures" class="">693972.63<span class="Apple-tab-span" style="white-space:pre">
</span>695281.52 -35.37</span></div>
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<div class="">The result is a little bit different from what you expect. Maybe because I use egm08 and you expect another Geoid model.</div>
<div class="">Doing the same way you try this (with proj program) I can’t get the correct use of the GeoidGrid. Why????</div>
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<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class="">
<span style="font-variant-ligatures: no-common-ligatures" class="">echo -6.6 53 21 | proj +proj=tmerc +lat_0=53.5 +lon_0=-8 +k=0.99982 +x_0=600000 +y_0=750000 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +geoidgrids=egm08_25_rg.gtx +units=m +no_defs</span></div>
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<span style="font-variant-ligatures: no-common-ligatures" class="">693972.63<span class="Apple-tab-span" style="white-space:pre">
</span>695281.52 21</span></div>
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<div class="">But your problem in that you seem to enter with an ellipsoid elevation and want to get geoid elevation at the end of the process. For this you need to install the geoidgrids on your PROJ installation, and use it as indicated here but with cs2cs
program.</div>
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<div class="">Alain </div>
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<blockquote type="cite" class="">
<div class="">Le 22 août 2018 à 11:19, Elmir Jagudin <<a href="mailto:elmir.jagudin@gmail.com" class="">elmir.jagudin@gmail.com</a>> a écrit :</div>
<br class="Apple-interchange-newline">
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<div dir="ltr" class="">Hi<br class="">
<br class="">
I'm trying to convert a WGS84/ETRS89 positions in Ireland into a ITM (Irish Transverse Mercator) easting northings and OSGM15 elevations.<br class="">
<br class="">
Using the this commands:<br class="">
<br class="">
echo -6.6 53 21 | /proj \<br class="">
+proj=tmerc +lat_0=53.5 +lon_0=-8 +k=0.99982 +x_0=600000 +y_0=750000 +ellps=GRS80
<br class="">
+towgs84=0,0,0,0,0,0,0 +units=m +no_defs<br class="">
<br class="">
gives me:<br class="">
<br class="">
693972.63 695281.52 21<br class="">
<br class="">
The easting and northing are correct, however the elevation is not, the correct value is -35.15.<br class="">
<br class="">
Is it possible to use proj4 to calculate OSGM15 elevations? What should the proj-string be in that case?<br class="">
<br class="">
Or do i need to create a .gtx file for OSGM15?<br class="">
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Not sure how the elevations work in proj4, is there any documentation i could read?<br class="">
<br class="">
<br class="">
Thanks in advance,<br class="">
Elmir<br class="">
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