<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Jochem,<div class=""><br class=""></div><div class="">Coincidentally I am working on a similar grid for Denmark. I’ve used VERTICAL_OFFSET_VERTICAL_TO_VERTICAL, which seems to fit the bill. </div><div class=""><br class=""></div><div class="">/Kristian</div><div class=""><br class=""></div><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On 16 Mar 2023, at 17.34, Lesparre, Jochem via PROJ <<a href="mailto:proj@lists.osgeo.org" class="">proj@lists.osgeo.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta charset="UTF-8" class=""><div class="WordSection1" style="page: WordSection1; caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Hi PROJ mailing list,<o:p class=""></o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-GB" class="">I am making a Geodetic TIFF Grid for the transformation between ETRS89 and Lowest Astronomical Tide of the Netherlands (<a href="https://epsg.org/crs_9289/ETRS89-LAT-NL-depth.html" style="color: rgb(5, 99, 193); text-decoration: underline;" class="">https://epsg.org/crs_9289/ETRS89-LAT-NL-depth.html</a>).<o:p class=""></o:p></span></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-GB" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-GB" class="">So this Geodetic TIFF Grid is of the type “VERTICAL_OFFSET_GEOGRAPHIC_TO_VERTICAL”. The description “geoid_undulation” seems unfitting, but if I choose something else like “lowest_astronomical_tide” PROJ doesn’t accept it:<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0cm 35.4pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-GB" style="font-size: 10pt; font-family: Consolas;" class="">proj_create: Error 1029 (File not found or invalid): pipeline: Pipeline: Bad step definition: proj=vgridshift (File not found or invalid)<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0cm 35.4pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-GB" style="font-size: 10pt; font-family: Consolas;" class="">cct: Bad transformation arguments - (File not found or invalid)<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0cm 35.4pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-GB" style="font-size: 10pt; font-family: Consolas;" class=""> 'cct -h' for help<o:p class=""></o:p></span></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-GB" class="">Should I use the description “geoid_undulation” nevertheless, should I use something else for type instead of “VERTICAL_OFFSET_GEOGRAPHIC_TO_VERTICAL”, or should I make a feature request to support a description name for “hydroid” models?<o:p class=""></o:p></span></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-GB" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-GB" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-GB" class="">Another, thing I was wondering is how to deal with the difference between height and depth. Should the Geodetic TIFF Grid specify ETRS89 + LAT NL depth (EPSG:9289) as target CRS, so EPSG would only have to make transformation code and a tif equivalent of the transformation method “</span><span lang="EN-GB" style="font-size: 10pt; font-family: Arial, sans-serif; color: rgb(48, 48, 48); background-color: white;" class="">Geog3D to Geog2D+Depth (txt)” (</span><span lang="EN-GB" class=""><a href="https://epsg.org/coord-operation-method_1115/Geog3D-to-Geog2D-Depth-txt.html" style="color: rgb(5, 99, 193); text-decoration: underline;" class="">https://epsg.org/coord-operation-method_1115/Geog3D-to-Geog2D-Depth-txt.html</a>)? Or should the Geodetic TIFF Grid specify ETRS89 + LAT NL height (for which no EPSG code is available yet) as target CRS? I case of the latter, EPSG would need to make transformation code and an equivalent of the transformation method “Geog3D to Geog2D+GravityRelatedHeight (txt)</span><span lang="EN-GB" style="font-size: 10pt; font-family: Arial, sans-serif; color: rgb(48, 48, 48); background-color: white;" class="">” (<a href="https://epsg.org/coord-operation-method_1098/Geog3D-to-Geog2D-GravityRelatedHeight-txt.html" style="color: rgb(5, 99, 193); text-decoration: underline;" class="">https://epsg.org/coord-operation-method_1098/Geog3D-to-Geog2D-GravityRelatedHeight-txt.html</a></span><span lang="EN-GB" class="">), but also have to add an additional CRS code for LAT NL height, a Compound code ETRS89 + LAT NL height, and a transformation code LAT NL height to LAT NL depth based on “Height Depth Reversal” (<a href="https://epsg.org/coord-operation-method_1068/Height-Depth-Reversal.html" style="color: rgb(5, 99, 193); text-decoration: underline;" class="">https://epsg.org/coord-operation-method_1068/Height-Depth-Reversal.html</a>).<o:p class=""></o:p></span></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-GB" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-GB" class="">Best regards, Jochem<o:p class=""></o:p></span></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-GB" class=""><o:p class=""> </o:p></span></div></div><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; 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