<div dir="ltr"><br><div class="gmail_quote"><div dir="ltr">On Wed, Aug 22, 2018 at 12:12 PM Alain Orsoni <<a href="mailto:Alain.Orsoni@ign.fr">Alain.Orsoni@ign.fr</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<div>Hi,</div>
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<div>Trying to answer with my knowledge :</div>
<div>On my computer I can do this transform in this way</div>
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<span style="font-variant-ligatures:no-common-ligatures">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">693972.63<span class="gmail-m_-5031490941191905987Apple-tab-span" style="white-space:pre-wrap">
</span>695281.52 -35.37</span></div>
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<div>The result is a little bit different from what you expect. Maybe because I use egm08 and you expect another Geoid model.</div></div></blockquote><br></div><div class="gmail_quote">Aha, cool. This looks like the right path for me.<br><br>Yes, the OSGM15 is probably using slightly different geoid model. I'll try to create gtx file for OSGM15.<br><br></div><div class="gmail_quote">If anyone is curious, there is a document the describes OSGM15 here:<br><a href="https://www.ordnancesurvey.co.uk/business-and-government/help-and-support/navigation-technology/os-net/formats-for-developers.html">https://www.ordnancesurvey.co.uk/business-and-government/help-and-support/navigation-technology/os-net/formats-for-developers.html</a><br><br></div><div class="gmail_quote">/Elmir<br></div></div>