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diff --git a/.github/README.md b/.github/README.md
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+../README.DATUMGRID
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diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
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+# How to contribute to proj-datumgrid-geotiff
+
+Consult [PROJ CONTRIBUTING.md](https://github.com/OSGeo/proj.4/blob/master/CONTRIBUTING.md)
+for general principles.
+
+TODO. Mention the scripts currently at https://github.com/rouault/sample_proj_gtiff_grids/
diff --git a/README.DATUMGRID b/README.DATUMGRID
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+# PROJ-DATUMGRID-GEOTIFF
+
+The files in this package are in cloud-optimized GeoTIFF format and can be
+unpacked in the PROJ data directory of PROJ 7 or later.
+For an installed PROJ this may be /usr/local/share/proj or /usr/share/proj
+on unix style operating systems.
+
+## About the Datum Grid package
+
+The datum grid package for PROJ is maintained on the OSGeo proj-datumgrid-geotiff
+repository on [GitHub](https://github.com/OSGeo/proj-datumgrid-geotiff).
+
+It contains shift grids for horizontal and vertical coordinate transformations.
+
+All grids in the package are released under
+permissive licenses. New grids are accepted into the package as long as
+they are released under a license that is compatible with the [Open Source
+Definition](https://opensource.org/osd-annotated) and the source of the grid
+is clearly stated and verifiable. Suitable licenses include:
+
+  * Public domain
+  * X/MIT
+  * BSD 2/3/4 clause
+  * CC0
+  * CC-BY (v3.0 or later)
+  * CC-BY-SA (v3.0 or later)
+
+Consult [CONTRIBUTING.md](https://github.com/OSGeo/proj-datumgrid-geotiff/blob/master/CONTRIBUTING.md) to submit a new grid.
+
+## Cloud usage
+
+Those grids can be retrieved from cloud storage (AWS Public datasets) as
+described in
+https://github.com/rouault/PROJ/blob/rfc4_remote_and_geotiff_grid/docs/source/community/rfc/rfc-4.rst#network-access-to-grids
+
+## Content
+
+All grid files should be put in a flat way in the PROJ data directory. They
+will be also organized in a flat way on cdn.proj.org.
+
+However for clarity of this repository, we have organized them by producer / agency.
+Each file is in a subdirectory whose name follows {country_code}_{agency_name}.
+For example us_noaa for files originating from US NOAA.
+
+[at_bev: Austria BEV](https://github.com/OSGeo/proj-datumgrid-geotiff/blob/master/at_bev/README.at_bev)
+[au_geoau: Australia Geosciences Australia](https://github.com/OSGeo/proj-datumgrid-geotiff/blob/master/au_geoau/README.au_geoau)
+[au_icsm: Australia ICSM](https://github.com/OSGeo/proj-datumgrid-geotiff/blob/master/au_icsm/README.au_icsm)
+[be_ign: Belgium IGN](https://github.com/OSGeo/proj-datumgrid-geotiff/blob/master/be_ign/README.be_ign)
+[ca_nrc: Canada NRC](https://github.com/OSGeo/proj-datumgrid-geotiff/blob/master/ca_nrc/README.ca_nrc)
+[ch_swisstopo: Switzerland Swissstopo](https://github.com/OSGeo/proj-datumgrid-geotiff/blob/master/ch_swisstopo/README.ch_swisstopo)
+[de_bkg: Germany BKG](https://github.com/OSGeo/proj-datumgrid-geotiff/blob/master/de_bkg/README.de_bkg)
+[de_geogsn: Germany GeoSN](https://github.com/OSGeo/proj-datumgrid-geotiff/blob/master/de_geogsn/README.de_geogsn)
+[de_lgl: Germany LGL](https://github.com/OSGeo/proj-datumgrid-geotiff/blob/master/de_lgl/README.de_lgl)
+[dk_sdfe: Denmark SDFE](https://github.com/OSGeo/proj-datumgrid-geotiff/blob/master/dk_sdfe/README.dk_sdfe)
+[fr_ign: France IGN](https://github.com/OSGeo/proj-datumgrid-geotiff/blob/master/fr_ign/README.fr_ign)
+[nz_linz: New Zealand LINZ](https://github.com/OSGeo/proj-datumgrid-geotiff/blob/master/nz_linz/README.nz_linz)
+[pt_dgt: Portugal DGT](https://github.com/OSGeo/proj-datumgrid-geotiff/blob/master/pt_dgt/README.pt_dgt)
+[se_lantmateriet: Sweden Lantmateriet](https://github.com/OSGeo/proj-datumgrid-geotiff/blob/master/se_lantmateriet/README.se_lantmateriet)
+[uk_os: UK OS](https://github.com/OSGeo/proj-datumgrid-geotiff/blob/master/uk_os/README.uk_os)
+[us_nga: USA NGA](https://github.com/OSGeo/proj-datumgrid-geotiff/blob/master/us_nga/README.us_nga)
+[us_noaa: USA NOAA](https://github.com/OSGeo/proj-datumgrid-geotiff/blob/master/us_noaa/README.us_noaa)
+[us_usgs: USA USGS](https://github.com/OSGeo/proj-datumgrid-geotiff/blob/master/us_usgs/README.us_usgs)
diff --git a/at_bev/.github/README.md b/at_bev/.github/README.md
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+../README.at_bev
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diff --git a/at_bev/README.at_bev b/at_bev/README.at_bev
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+# README.at_bev
+
+The files in this section result from the conversion of datasets originating
+from [Austria Bundesamt für Eich- und Vermessungswessen](www.bev.gv.at)
+
+## Included grids
+
+### Austria: MGI -> ETRS89
+
+*Source*: [BEV](http://www.bev.gv.at/portal/page?_pageid=713,2157075&_dad=portal&_schema=PORTAL)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Creative Commons Attribution 4.0](https://creativecommons.org/licenses/by/4.0/)
+
+* AT_GIS_GRID.tif
diff --git a/au_geoau/.github/README.md b/au_geoau/.github/README.md
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+../README.au_geoau
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diff --git a/au_geoau/README.au_geoau b/au_geoau/README.au_geoau
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+# README.au_geoau
+
+The files in this section result from the conversion of datasets originating
+from [Geoscience Australia]G(http://www.ga.gov.au)
+
+### Australia: AUSGeoid98: GDA94 -> AHD height
+
+*Source*: [Geoscience Australia](http://www.ga.gov.au/ausgeoid/comp.html)  
+*Format*: GeoTIFF converted from GTX  
+*License*: [Creative Commons Attribution 4.0]  
+*Converter*: gdal_translate -of GTX AUSGeoid98.gsb AUSGeoid98.gtx -b 1 
+
+* AUSGeoid98.tif
+
+### Australia: AUSGeoid09: GDA94 -> AHD height
+
+*Source*: [Geoscience Australia](http://www.ga.gov.au/ausgeoid/comp.html)  
+*Format*: GeoTIFF converted from GTX  
+*License*: [Creative Commons Attribution 4.0]  
+*Converter*: gdal_translate -of GTX AUSGeoid09_V1.01.gsb AUSGeoid09_V1.01.gtx -b 1 
+
+Uses AusGeoid09 model which uses bi-cubic interpolation; bi-linear interpolation
+of the grid file will give results agreeing to within 1cm 99.97% of the time.
+
+* AUSGeoid09_V1.01.tif
+
+### Australia: AUSGeoid2020: GDA2020 -> AHD height
+
+*Source*: [Geoscience Australia](http://www.ga.gov.au/ausgeoid/comp.html)  
+*Format*: GeoTIFF converted from GTX  
+*License*: [Creative Commons Attribution 4.0]  
+*Converter*: gdal_translate AUSGeoid2020_20180201.gsb tmp.tif -a_nodata -999 -b 1 && gdalwarp tmp.tif AUSGeoid2020_20180201.gtx -dstnodata -88.8888015747070312 -of GTX
+
+Uses AusGeoid2020 model.
+
+* AUSGeoid2020_20180201.tif
diff --git a/au_icsm/.github/README.md b/au_icsm/.github/README.md
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+../README.au_icsm
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diff --git a/au_icsm/README.au_icsm b/au_icsm/README.au_icsm
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+# README.au_geoau
+
+The files in this section result from the conversion of datasets originating
+from [ICSM]
+
+## Included grids
+
+### Australia: AGD66 -> GDA94
+
+*Source*: [ICSM]  
+*Format*: GeoTIFF convered from NTv2  
+*License*: [Creative Commons Attribution 4.0]
+
+Full national coverage two-way transformation file – see Appendix B
+in the [GDA2020 Technical Manual] for details.
+
+* A66_National_13_09_01.tif
+
+### Australia: AGD84 -> GDA94
+
+*Source*: [ICSM]  
+*Format*: GeoTIFF convered from NTv2  
+*License*: [Creative Commons Attribution 4.0]
+
+Full coverage two-way transformation file in those states that
+originally adopted AGD84 - West Australia, South Australia, Queensland – see
+Appendix B in the [GDA2020 Technical Manual] for details.
+
+* National_84_02_07_01.tif
+
+### Australia: GDA94 -> GDA2020
+
+*Source*: [ICSM]  
+*Format*: GeoTIFF convered from NTv2  
+*License*: [Creative Commons Attribution 4.0]
+
+Full national coverage two-way transformation files – See Sections 3.2
+and 3.7 in the [GDA2020 Technical Manual] for details.
+Table 3.4 details which grid to use.
+
+* GDA94_GDA2020_conformal.tif
+* GDA94_GDA2020_conformal_and_distortion.tif
+* GDA94_GDA2020_conformal_christmas_island.tif
+* GDA94_GDA2020_conformal_cocos_island.tif
+
+[Creative Commons Attribution 4.0]: https://creativecommons.org/licenses/by/4.0/
+[GDA2020 Technical Manual]: http://www.icsm.gov.au/datum/gda2020-and-gda94-technical-manuals
+[ICSM]: https://github.com/icsm-au/transformation_grids
diff --git a/be_ign/.github/README.md b/be_ign/.github/README.md
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+../README.be_ign
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diff --git a/be_ign/README.be_ign b/be_ign/README.be_ign
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+# README.be_ign
+
+The files in this section result from the conversion of datasets originating
+from [IGN Belgium](http://www.ngi.be)
+
+## Included grids
+
+### Belgium: BD72 -> ETRS89
+
+Grid transformation from Belgium Datum 72 to ETRS89 in Belgium.
+
+*Source*: [IGN](http://www.ngi.be/Common/Lambert2008/NTv2.zip)
+*Format*: GeoTIFF converted from NTv2
+*License*: [Creative Commons Attribution 4.0](https://creativecommons.org/licenses/by/4.0/)
+*Credit*: (c)2014-2016 Grid created by Nicolas SIMON.
+
+It provides an accuracy better than 5mm in 99.6% of validation points and a
+worst case of 1.3 cm outside the border.
+Recommended to transform from Belgian Lambert 72 (EPSG:31370) to Belgian Lambert 2008 (EPSG:3812)
+Documentation in French: (http://www.ngi.be/FR/FR2-1-7.shtm)
+Documentation in Dutch:  (http://www.ngi.be/NL/NL2-1-7.shtm)
+
+* bd72lb72_etrs89lb08.tif
diff --git a/ca_nrc/.github/README.md b/ca_nrc/.github/README.md
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+../README.ca_nrc
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diff --git a/ca_nrc/README.ca_nrc b/ca_nrc/README.ca_nrc
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+# README.ca_nrc
+
+The files in this section result from the conversion of datasets originating
+from  [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod)
+
+## Included grids
+
+### Canada: NAD27 -> NAD83
+
+*Source*: [Natural Resources Canada](https://open.canada.ca/data/en/dataset/b3534942-31ea-59cf-bcc3-f8dc4875081a)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)
+
+Transform between NAD27 and NAD83 in Canada.
+
+* ntv2_0.gsb
+
+### Canada: Alberta: NAD83(Original) --> NAD83(CSRS) 2002
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=ABCSRSV4)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4269 (NAD83)  
+*Target CRS*: EPSG:8246 (NAD83(CSRS)v4)  
+*Used by*: [EPSG:9244 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9244)
+
+* ABCSRSV4.tif
+
+### Canada: British Columbia (CRD): NAD27 --> NAD83(CSRS) 1997
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=CRD27_00)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4267 (NAD27)  
+*Target CRS*: EPSG:8240 (NAD83(CSRS)v3)  
+*Used by*: [EPSG:9113 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9113)
+
+* CRD27_00.tif
+
+### Canada: British Columbia (CRD): NAD83(Original) --> NAD83(CSRS) 1997
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=CRD93_00)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4269 (NAD83)  
+*Target CRS*: EPSG:8240 (NAD83(CSRS)v3)  
+*Used by*: [EPSG:9117 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9117)
+
+* CRD93_00.tif
+
+### Canada: British Columbia (Vancouver Island): NAD83(Original) --> NAD83(CSRS) 1997
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=NVI93_05)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4269 (NAD83)  
+*Target CRS*: EPSG:8240 (NAD83(CSRS)v3)  
+*Used by*: [EPSG:9118 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9118)  
+
+* NVI93_05.tif
+
+### Canada: British Columbia (CRD): NAD27 --> NAD83(CSRS) 2002
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=BC_27_05)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4267 (NAD27)  
+*Target CRS*: EPSG:8246 (NAD83(CSRS)v4)  
+*Used by*: [EPSG:9115 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9115)
+
+* BC_27_05.tif
+
+### Canada: British Columbia (CRD): NAD83(Original) --> NAD83(CSRS) 2002
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=BC_93_05)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4269 (NAD83)  
+*Target CRS*: EPSG:8246 (NAD83(CSRS)v4)  
+*Used by*: [EPSG:9119 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9119)
+
+* BC_93_05.tif
+
+### Canada: New Brunswick: ATS77 --> NAD83(CSRS) 1997
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=NB7783v2)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4122 (ATS77)  
+*Target CRS*: EPSG:8237 (NAD83(CSRS)v2)  
+*Used by*: [EPSG:9237 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9237)
+
+* NB7783v2.tif
+
+### Canada: New Brunswick: NAD27 --> NAD83(CSRS) 1997
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=NB2783v2)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4267 (NAD27)  
+*Target CRS*: EPSG:8237 (NAD83(CSRS)v2)  
+*Used by*: [EPSG:9238 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9238)
+
+* NB2783v2.tif
+
+### Canada: Nova Scotia: ATS77 --> NAD83(Original)
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=GS7783)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4122 (ATS77)  
+*Target CRS*: EPSG:4269 (NAD83)  
+*Used by*: [EPSG:9105 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9105)
+
+* GS7783.tif
+
+### Canada: Nova Scotia: ATS77 --> NAD83(CSRS) 2010
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=NS778302)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4122 (ATS77)  
+*Target CRS*: EPSG:8252 (NAD83(CSRS)v6)  
+*Used by*: [EPSG:9106 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9106)
+
+* NS778302.tif
+
+### Canada: Ontario: NAD27 --> NAD83(CSRS) 1997
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=ON27CSv1)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4267 (NAD27)  
+*Target CRS*: EPSG:8240 (NAD83(CSRS)v3)  
+*Used by*: [EPSG:9107 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9107)
+
+* ON27CSv1.tif
+
+### Canada: Ontario: NAD27(MAY76) --> NAD83(CSRS) 1997
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=ON76CSv1)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4608 (NAD27(76))  
+*Target CRS*: EPSG:8240 (NAD83(CSRS)v3)  
+*Used by*: [EPSG:9109 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9109)
+
+* ON76CSv1.tif
+
+### Canada: Ontario: NAD83(Original) --> NAD83(CSRS) 1997
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=ON83CSv1)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4269 (NAD83)  
+*Target CRS*: EPSG:8240 (NAD83(CSRS)v3)  
+*Used by*: [EPSG:9110 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9110)
+
+* ON83CSv1.tif
+
+### Canada: Ontario (Toronto): NAD27 --> NAD83(CSRS) 1997
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=TO27CSv1)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4267 (NAD27)  
+*Target CRS*: EPSG:8240 (NAD83(CSRS)v3)  
+*Used by*: No EPSG transformation code at the time of writing
+
+* TO27CSv1.tif
+
+### Canada: Prince Edward Island: ATS77 --> NAD83(CSRS) 1997
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=PE7783V2)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4122 (ATS77)  
+*Target CRS*: EPSG:8237 (NAD83(CSRS)v2)  
+*Used by*: [EPSG:9236 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9236)
+
+* PE7783V2.tif
+
+### Canada: Quebec: NAD27 --> NAD83(CSRS) 1997
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=NA27SCRS)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4267 (NAD27)  
+*Target CRS*: EPSG:8237 (NAD83(CSRS)v2)  
+*Used by*: [EPSG:9239 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9239)  
+*Used by*: [EPSG:1692 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::1692) for NAD27 -> WGS84
+
+* NA27SCRS.tif (also known as QUE27-98.gsb by EPSG for NAD27 -> WGS84)
+
+### Canada: Quebec: NAD27(CGQ77) --> NAD83(CSRS) 1997
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=CQ77SCRS)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4609 (NAD27(CGQ77))  
+*Target CRS*: EPSG:8237 (NAD83(CSRS)v2)  
+*Used by*: [EPSG:1575 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::1575)  
+*Used by*: [EPSG:1691 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::1691) for NAD27(CGQ77) -> WGS84
+
+* CQ77SCRS.tif (also known as CQ77NA83.GSB by EPSG)
+
+### Canada: Quebec: NAD83(Original) --> NAD83(CSRS) 1997
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=NA83SCRS)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4269 (NAD83)  
+*Target CRS*: EPSG:8237 (NAD83(CSRS)v2)  
+*Used by*: [EPSG:9241 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9241)  
+*Used by*: [EPSG:1696 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::1696) for NAD83 -> WGS84
+
+* NA83SCRS.tif (also known as NAD83-98.gsb by EPSG for NAD83 -> WGS84)
+
+### Canada: Saskatchewan: NAD27 --> NAD83(CSRS) 1997
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=SK27-98)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4267 (NAD27)  
+*Target CRS*: EPSG:8240 (NAD83(CSRS)v3)  
+*Used by*: [EPSG:9242 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9242)  
+*Used by*: [EPSG:1703 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::1703) for NAD27 -> WGS84
+
+* SK27-98.tif
+
+### Canada: Saskatchewan: NAD83(Original) --> NAD83(CSRS) 1997
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=SK83-98)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4269 (NAD83)  
+*Target CRS*: EPSG:8240 (NAD83(CSRS)v3)  
+*Used by*: [EPSG:9243 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9243)  
+*Used by*: [EPSG:1697 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::1697) for NAD83 -> WGS84
+
+* SK83-98.tif
+
+### Canada: CGVD28 height --> NAD83(CSRS)
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=HT2_2010)  
+*Format*: GeoTIFF converted from GTX  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:4955 (NAD83(CSRS))  
+*Target CRS*: EPSG:5713 (CGVD28 height)  
+*Used by*: [EPSG:9123 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9123)
+
+* HT2_2010v70.tif
+
+### Canada: CGVD2013(CGG2013a) height --> NAD83(CSRS)
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=CGG2013n83a)  
+*Format*: GeoTIFF converted from GTX  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:8251 (NAD83(CSRS)v6)  
+*Target CRS*: EPSG:9245 (CGVD2013(CGG2013a) height)  
+*Used by*: [EPSG:9247 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9247)
+
+* CGG2013an83.tif
+
+### Canada: CGVD2013(CGG2013a) height --> ITRF2008
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=CGG2013i08a)  
+*Format*: GeoTIFF converted from GTX  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:7911 (ITRF2008)  
+*Target CRS*: EPSG:9245 (CGVD2013(CGG2013a) height)  
+*Used by*: [EPSG:9125 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9125)
+
+* CGG2013ai08.tif
+
+### Canada: CGVD2013(CGG2013) height --> NAD83(CSRS) (superseded by CGVD2013(CGG2013a) height --> NAD83(CSRS))
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=CGG2013n83)  
+*Format*: GeoTIFF converted from GTX  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:8251 (NAD83(CSRS)v6)  
+*Target CRS*: EPSG:6647 (CGVD2013(CGG2013) height)  
+*Used by*: [EPSG:9246 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9246)
+
+* CGG2013n83.tif
+
+### Canada: CGVD2013(CGG2013) height --> ITRF2008 (superseded by CGVD2013(CGG2013a) height --> ITRF2008)
+
+*Source*: [Natural Resources Canada](https://webapp.geod.nrcan.gc.ca/geod/process/download-helper.php?file_id=CGG2013i08)  
+*Format*: GeoTIFF converted from GTX  
+*License*: [Open Government Licence - Canada](http://open.canada.ca/en/open-government-licence-canada)  
+*Source CRS*: EPSG:7911 (ITRF2008)  
+*Target CRS*: EPSG:6647 (CGVD2013(CGG2013) height)  
+*Used by*: [EPSG:9124 Transformation](https://www.epsg-registry.org/export.htm?gml=urn:ogc:def:coordinateOperation:EPSG::9124)
+
+* CGG2013i08.tif
diff --git a/ch_swisstopo/.github/README.md b/ch_swisstopo/.github/README.md
new file mode 120000
index 0000000..c650f31
--- /dev/null
+++ b/ch_swisstopo/.github/README.md
@@ -0,0 +1 @@
+../README.ch_swisstopo
\ No newline at end of file
diff --git a/ch_swisstopo/README.ch_swisstopo b/ch_swisstopo/README.ch_swisstopo
new file mode 100644
index 0000000..d229ace
--- /dev/null
+++ b/ch_swisstopo/README.ch_swisstopo
@@ -0,0 +1,25 @@
+# README.ch_swisstopo
+
+The files in this section result from the conversion of datasets originating
+from [Swisstopo](ttps://www.swisstopo.admin.ch)
+
+## Included grids
+
+### Switzerland: LV03 (system CH1903) -> LV95 (system CH1903+)
+
+*Source*: [swisstopo](https://www.swisstopo.admin.ch/en/knowledge-facts/surveying-geodesy/reference-frames/transformations-position.html)
+*Format*: GeoTIFF converted from NTv2.0 (.gsb)
+*License*: [Creative Commons CC0 1.0 Universal](https://creativecommons.org/publicdomain/zero/1.0/legalcode)
+*Credit*: (c) 2007 swisstopo
+
+Recommended to transform from Swiss reference frame LV03 (system CH1903, EPSG:21781) to Swiss reference frame LV95 (system CH1903+, EPSG:2056).
+LV95 is aligned to ETRF93, but shifted by several 100 meters.
+CH1903+ is the official reference system for federal surveying and for all national geobasis data regulated by federal law since 2017.
+CHENyx06a.gsb gives corrections (distorsions between LV03 and LV95) in CH1903, CHENyx06_ETRS.gsb gives the corrections in ETRS.
+Several transformation services are available on https://www.swisstopo.admin.ch/en/maps-data-online/calculation-services.html
+(web forms and REST web geoservices) to support the exact transformation procedure between CH1903 and CH1903+
+using the REFRAME algorithm (finite element transformation).
+The difference between the grid and finite element transformation is on a level of below several millimeters.
+
+* CHENyx06a.tif
+* CHENyx06_ETRS.tif
diff --git a/de_bkg/.github/README.md b/de_bkg/.github/README.md
new file mode 120000
index 0000000..4430d95
--- /dev/null
+++ b/de_bkg/.github/README.md
@@ -0,0 +1 @@
+../README.de_bkg
\ No newline at end of file
diff --git a/de_bkg/README.de_bkg b/de_bkg/README.de_bkg
new file mode 100644
index 0000000..bb80779
--- /dev/null
+++ b/de_bkg/README.de_bkg
@@ -0,0 +1,16 @@
+# README.de_bkg
+
+The files in this section result from the conversion of datasets originating
+from [BKG](http://crs.bkg.bund.de/crseu/crs/descrtrans/BeTA/de_dhdn2etrs_beta.php)
+
+## Included grids
+
+### Germany: DE_DHDN -> ETRS89
+
+*Source*: [BKG](http://crs.bkg.bund.de/crseu/crs/descrtrans/BeTA/de_dhdn2etrs_beta.php)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: Free redistribution is allowed and welcome
+
+Grid transformation from DE_DHDN to ETRS89 in Germany.
+
+* BETA2007.tif
diff --git a/de_geosn/.github/README.md b/de_geosn/.github/README.md
new file mode 120000
index 0000000..88c19b3
--- /dev/null
+++ b/de_geosn/.github/README.md
@@ -0,0 +1 @@
+../README.de_geosn
\ No newline at end of file
diff --git a/de_geosn/README.de_geosn b/de_geosn/README.de_geosn
new file mode 100644
index 0000000..2e78473
--- /dev/null
+++ b/de_geosn/README.de_geosn
@@ -0,0 +1,14 @@
+# README.de_geosn
+
+The files in this section result from the conversion of datasets originating
+from [GeoSN](https://www.landesvermessung.sachsen.de)
+
+## Included grids
+
+### Germany (Saxony): RD/83 to ETRS89
+
+*Source*: [GeoSN](https://www.landesvermessung.sachsen.de/download-5608.html?_cp=%7B%22accordion-content-4389%22%3A%7B%222%22%3Atrue%7D%2C%22previousOpen%22%3A%7B%22group%22%3A%22accordion-content-4389%22%2C%22idx%22%3A2%7D%7D)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Data licence Germany – attribution – version 2.0](https://www.govdata.de/dl-de/by-2-0)
+
+* NTv2_SN.tif
diff --git a/de_lgl/.github/README.md b/de_lgl/.github/README.md
new file mode 120000
index 0000000..db29636
--- /dev/null
+++ b/de_lgl/.github/README.md
@@ -0,0 +1 @@
+../README.de_lgl
\ No newline at end of file
diff --git a/de_lgl/README.de_lgl b/de_lgl/README.de_lgl
new file mode 100644
index 0000000..73068fd
--- /dev/null
+++ b/de_lgl/README.de_lgl
@@ -0,0 +1,16 @@
+# README.de_geosn
+
+The files in this section result from the conversion of datasets originating
+from [LGL](https://www.lgl-bw.de)
+
+## Included grids
+
+### Germany (Baden-Württemberg): DE_DHDN -> ETRS89
+
+*Source*: [LGL](https://www.lgl-bw.de/lgl-internet/opencms/de/05_Geoinformation/Liegenschaftskataster/ETRS89-UTM/)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Data licence Germany – attribution – version 2.0](https://www.govdata.de/dl-de/by-2-0)
+
+Grid transformation from DE_DHDN to ETRS89 for Baden-Württemberg.
+
+* BWTA2017.tif
diff --git a/dk_sdfe/.github/README.md b/dk_sdfe/.github/README.md
new file mode 120000
index 0000000..39077f5
--- /dev/null
+++ b/dk_sdfe/.github/README.md
@@ -0,0 +1 @@
+../README.dk_sdfe
\ No newline at end of file
diff --git a/dk_sdfe/README.dk_sdfe b/dk_sdfe/README.dk_sdfe
new file mode 100644
index 0000000..cc4f9c8
--- /dev/null
+++ b/dk_sdfe/README.dk_sdfe
@@ -0,0 +1,106 @@
+# README.dk_sdfe
+
+The files in this section result from the conversion of datasets originating
+from [Agency for Data Supply and Efficiency](https://github.com/NordicGeodesy/NordicTransformations)  
+
+## Included grids
+
+### Denmark: DVR90 heights -> ETRS89 ellipsoidal heights
+
+*Source*: [Agency for Data Supply and Efficiency](https://github.com/NordicGeodesy/NordicTransformations)  
+*Format*: GeoTIFF converted from GTX  
+*License*: [Creative Commons Attribution 4.0](https://creativecommons.org/licenses/by/4.0/)
+
+Transform local height system DVR90 (EPSG:5799) to ETRS89 ellipsoidal heights (EPSG:4937). The horizontal
+grid coordinates are referenced to ETRS89.
+
+* dvr90.tif
+
+### Denmark: DNN heights -> ETRS89 ellipsoidal heights
+
+*Source*: [Agency for Data Supply and Efficiency](https://github.com/NordicGeodesy/NordicTransformations)  
+*Format*: GeoTIFF converted from GTX  
+*License*: [Creative Commons Attribution 4.0](https://creativecommons.org/licenses/by/4.0/)
+
+Transform local height system DNN (EPSG:5733) to ETRS89 ellipsoidal heights (EPSG:4937). The horizontal
+grid coordinates are referenced to ETRS89.
+
+* dnn.tif
+
+### Faroe Islands: FVR09 heights -> ETRS89 ellipsoidal heights
+
+*Source*: [Agency for Data Supply and Efficiency](https://github.com/NordicGeodesy/NordicTransformations)  
+*Format*: GeoTIFF converted from GTX  
+*License*: [Creative Commons Attribution 4.0](https://creativecommons.org/licenses/by/4.0/)
+
+Transform local height system FVR09 (EPSG:5317) to ETRS89 ellipsoidal heights (EPSG:4937). The horizontal
+grid coordinates are referenced to ETRS89.
+
+* fvr09.tif
+
+### Nordic+Baltic countries: Deformation model
+
+*Source*: [The Nordic Geodetic Commission](https://github.com/NordicGeodesy/NordicTransformations)  
+*Format*: CTable2 and GTX  
+*License*: [Creative Commons Attribution 4.0](https://creativecommons.org/licenses/by/4.0/)
+
+Deformation model covering the Nordic and Baltic countries. Used in
+transformations between global reference frames and the local realisations
+of ETRS89 in the Nordic and Baltic countries. See the `NKG` init-file for
+examples of use.
+
+* nkgrf03vel_realigned_xy.ct2
+* nkgrf03vel_realigned_z.gtx
+
+## Included init-files
+
+### Denmark: System definitions related to ETRS89
+
+*Source*: [Agency for Data Supply and Efficiency](https://github.com/NordicGeodesy/NordicTransformations)  
+*License*: [Creative Commons Attribution 4.0](https://creativecommons.org/licenses/by/4.0/)
+
+Init files with various transformations and conversions of relevance in
+Denmark. All definitions in the init file uses the local ETRS89 reference
+frame as a pivot datum. More information can be found in the
+[NordicTransformations](https://github.com/NordicGeodesy/NordicTransformations)
+repository. While the `.pol` files are init-files they are not supposed to be
+by themselves. The exist purely as helper files for the `DK` init-file.
+The `.pol` files holds polynomial constants used for transformations between
+Danish legacy coordinate reference systems and ETRS89.
+
+* DK
+* DK_bornholm.pol
+* DK_bridges.pol
+* DK_general.pol
+* DK_jutland.pol
+* DK_zealand.pol
+
+### The Faroe Islands: System definitions related to ETRS89
+
+*Source*: [Agency for Data Supply and Efficiency](https://github.com/NordicGeodesy/NordicTransformations)  
+*License*: [Creative Commons Attribution 4.0](https://creativecommons.org/licenses/by/4.0/)
+
+Init file with various transformations and conversions of relevance in
+The Faroe Islands. All definitions in the init file uses the local ETRS89
+reference frame as a pivot datum. More information can be found in the
+[NordicTransformations](https://github.com/NordicGeodesy/NordicTransformations)
+repository.
+
+* FO
+
+### Nordic+Baltic countries: ITRFxx -> Local ETRS89 realizations
+
+*Source*: [The Nordic Geodetic Commission](https://github.com/NordicGeodesy/NordicTransformations)  
+*License*: [Creative Commons Attribution 4.0](https://creativecommons.org/licenses/by/4.0/)
+
+Transformations to and from the common Nordic referenc frame NKG_ETRF00.
+This init-file describes transformations between global reference frames
+and NKG_ETRF00 as well as transformations from NKG_ERTF00 to the local
+realisations of ETRS89 in each of the countries involved with NKG.
+
+All transformations in this init-file uses the common Nordic frame as a
+pivot datum. Exempt from this dogma are transformations with labels
+starting with ``_``. Those transformations are "private" to this file and are
+only used as steps in more complicated transformations.
+
+* NKG
diff --git a/fr_ign/.github/README.md b/fr_ign/.github/README.md
new file mode 120000
index 0000000..bc50e4c
--- /dev/null
+++ b/fr_ign/.github/README.md
@@ -0,0 +1 @@
+../README.fr_ign
\ No newline at end of file
diff --git a/fr_ign/README.fr_ign b/fr_ign/README.fr_ign
new file mode 100644
index 0000000..798bc1f
--- /dev/null
+++ b/fr_ign/README.fr_ign
@@ -0,0 +1,79 @@
+# README.fr_ign
+
+The files in this section result from the conversion of datasets originating
+from [IGN](http://www.ign.fr/)
+
+## Included grids
+
+### France: NTF -> RGF93
+
+Grid transformation from NTF to RGF93 in France.
+
+*Source*: [IGN](http://www.ign.fr/)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [License Ouverte (in French)](https://www.etalab.gouv.fr/wp-content/uploads/2017/04/ETALAB-Licence-Ouverte-v2.0.pdf) / [Open License (English translation)](https://www.etalab.gouv.fr/wp-content/uploads/2014/05/Open_Licence.pdf)
+
+* ntf_r93.tif
+
+### French vertical grids
+
+*Source*: [IGN France](https://geodesie.ign.fr/index.php?page=grilles)  
+*Converter*: build_french_vgrids.sh  
+*Format*: GeoTIFF convered from GTX  
+*License*: [License Ouverte (in French)](https://www.etalab.gouv.fr/wp-content/uploads/2017/04/ETALAB-Licence-Ouverte-v2.0.pdf) / [Open License (English translation)](https://www.etalab.gouv.fr/wp-content/uploads/2014/05/Open_Licence.pdf)
+
+Grids to convert from national vertical datum to ellipsoidal height.
+
+Continental France an Corsica:
+* RAF09.tif: Continental France, NGF-IGN 1969 to RGF93 (ETRS89) (2009 version)
+* RAF18.tif: Continental France, NGF-IGN 1969 to RGF93 (ETRS89) (2018 version)
+* RAC09.tif: Corsica, NGF-IGN 1978 to RGF93 (ETRS89)
+
+French Antilles to RGAF09 (Réseau Géodésique des Antilles Françaises 2009):
+* RAGTBT2016.tif: Guadeloupe, IGN 1988 (GUADELOUPE) to RGAF09
+* RALD2016.tif: La Desirade, IGN 2008 LD (GUADELOUPE / LA DESIRADE) to RGAF09
+* RALS2016.tif: Les Saintes, IGN 1988 LS (GUADELOUPE / LES SAINTES) to RGAF09
+* RAMART2016.tif: Martinique, IGN 1987 (MARTINIQUE) to RGAF09
+* RAMG2016.tif: Marie Galante, IGN 1988 MG (GUADELOUPE / MARIE-GALANTE) to RGAF09
+* gg10_sbv2.tif: Saint Barthelemy, IGN 1988 SB (GUADELOUPE / SAINT-BARTHELEMY) to RGAF09
+* gg10_smv2.tif: Saint Martin, IGN 1988 SM (GUADELOUPE / SAINT-MARTIN) to RGAF09
+
+French Antilles to WGS 84 (RRAF: Réseau de Référence des Antilles Françaises):
+* ggg00v2.tif: Guadeloupe, IGN 1988 (GUADELOUPE) to WGS 84 (RRAF)
+* RALDW842016.tif: La Desirade, IGN 2008 LD (GUADELOUPE / LA DESIRADE) to WGS 84 (RRAF)
+* ggg00_lsv2.tif: Les Saintes, IGN 1988 LS (GUADELOUPE / LES SAINTES) to WGS 84 (RRAF)
+* ggg00_mgv2.tif: Marie Galante, IGN 1988 MG (GUADELOUPE / MARIE-GALANTE) to WGS 84 (RRAF)
+* ggm00v2.tif: Martinique, IGN 1987 (MARTINIQUE) to WGS 84 (RRAF)
+* ggg00_sbv2.tif: Saint Barthelemy, IGN 1988 SB (GUADELOUPE / SAINT-BARTHELEMY) to WGS 84 (RRAF)
+* ggg00_smv2.tif: Saint Martin, IGN 1988 SM (GUADELOUPE / SAINT-MARTIN) to WGS 84 (RRAF)
+
+Other:
+* ggguy15.tif: Guyane, NIVELLEMENT GENERAL DE GUYANE (NGG) 1977 to RGFG95 (RESEAU GEODESIQUE FRANCAIS DE GUYANE 1995)
+* ggker08v2.tif: Iles Kerguelen, IGN 1962 (KERGUELEN) to RGTAAF07 (RESEAU GEODESIQUE DES TAAF 2007)
+* ggm04v1.tif: Mayotte GGM04, SHOM 1953 (MAYOTTE) to RGM04 (RESEAU GEODESIQUE DE MAYOTTE 2004)
+* ggspm06v1.tif: Saint-Pierre et Miquelon (GGSPM06), DANGER 1950 (SAINT-PIERRE-ET-MIQUELON) to RGSPM06 (RESEAU GEODESIQUE DE SAINT-PIERRE-ET-MIQUELON 2006)
+* RAR07_bl.tif: La Reunion, IGN 1989 (REUNION) to RGR92 (RESEAU GEODESIQUE DE LA REUNION 1992)
+* RASPM2018.tif: Saint-Pierre et Miquelon (RASPM2018), DANGER 1950 (SAINT-PIERRE-ET-MIQUELON) to RGSPM06 (RESEAU GEODESIQUE DE SAINT-PIERRE-ET-MIQUELON 2006)
+* CGVD2013RGSPM06.tif: Saint-Pierre et Miquelon (CGVD2013RGSPM06), CGVD2013 to RGSPM06
+
+French Polynesia to RGPF (Réseau Géodésique de Polynésie Française)
+* ggpf02-Bora.tif: Bora bora, BORA_SAU 2001 to RGPF
+* ggpf02-Huahine.tif: Huahine, HUAHINE_SAU 2001 to RGPF
+* ggpf02-Maiao.tif: Maiao, MAIAO 2001 to RGPF
+* ggpf02-Maupiti.tif: Maupiti, MAUPITI_SAU 2001 to RGPF
+* ggpf02-Raiatea.tif: Raietea, RAIATEA_SAU 2001 to RGPF
+* ggpf02-Tahaa.tif: Tahaa, TAHAA_SAU 2001 to RGPF
+* ggpf02-Tupai.tif: Tupai, TUPAI 2001 to RGPF
+* ggpf05-HivaOa.tif: Hiva Oa, HIVA OA to RGPF
+* ggpf05-Nuku.tif: Nuku Hiva, NUKU HIVA ALTI to RGPF
+* ggpf08-Fakarava.tif: Fakarava, IGN 1966 (TAHITI) TO RGPF
+* ggpf08-Gambier.tif: Gambier, GAMBIER to RGPF
+* ggpf08-Hao.tif: Hao, HAO to RGPF
+* ggpf08-Mataiva.tif: Mataiva, MATAIVA to RGPF
+* ggpf08-Raivavae.tif: Raivavae, Raivavae to RGPF
+* ggpf08-Reao.tif: Reao, Reao to RGPF
+* ggpf08-Rurutu.tif: Rurutu, Ruruto to RGPF
+* ggpf08-Tikehau.tif: Tikehau, Tikehau to RGPF
+* ggpf08-Tubuai.tif: Tubuai, Tubuai to RGPF
+* ggpf10-Moorea.tif: Moorea, MOOREA 1981 (MOOREA_SAU 2001) to RGPF
+* ggpf10-Tahiti.tif: Tahiti, IGN 1966 (TAHITI) to RGPF
diff --git a/nz_linz/.github/README.md b/nz_linz/.github/README.md
new file mode 120000
index 0000000..f016c6e
--- /dev/null
+++ b/nz_linz/.github/README.md
@@ -0,0 +1 @@
+../README.nz_linz
\ No newline at end of file
diff --git a/nz_linz/README.nz_linz b/nz_linz/README.nz_linz
new file mode 100644
index 0000000..f35df84
--- /dev/null
+++ b/nz_linz/README.nz_linz
@@ -0,0 +1,17 @@
+# README.nz_linz
+
+The files in this section result from the conversion of datasets originating
+from [LINZ](https://www.linz.govt.nz)
+
+## Included grids
+
+### New Zealand: NZGD49 -> NZGD2000
+
+*Source*: [LINZ](https://www.linz.govt.nz/data/geodetic-system/download-geodetic-software/gd2000it-download)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Creative Commons Attribution 3.0 New Zealand](https://creativecommons.org/licenses/by/3.0/nz/)
+
+This grid file was computed by Land Information New Zealand at approximately
+a 20 km interval for the conversion between NZGD49 and NZGD2000.
+
+* nzgd2kgrid0005.tif
diff --git a/pt_dgt/.github/README.md b/pt_dgt/.github/README.md
new file mode 120000
index 0000000..ae947f6
--- /dev/null
+++ b/pt_dgt/.github/README.md
@@ -0,0 +1 @@
+../README.pt_dgt
\ No newline at end of file
diff --git a/pt_dgt/README.pt_dgt b/pt_dgt/README.pt_dgt
new file mode 100644
index 0000000..c5ac092
--- /dev/null
+++ b/pt_dgt/README.pt_dgt
@@ -0,0 +1,36 @@
+# README.pt_dgt
+
+The files in this section result from the conversion of datasets originating
+from [DG Territorio](http://www.dgterritorio.pt/)
+
+## Included grids
+
+### Portugal: Lisbon Datum -> ETRS89
+
+Grid transformation from Portuguese Lisbon Datum to ETRS89 in Portugal.
+
+*Source*: [DGT](http://www.dgterritorio.pt/cartografia_e_geodesia/geodesia/transformacao_de_coordenadas/grelhas_em_ntv2/)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Creative Commons Attribution 4.0](http://creativecommons.org/licenses/by/4.0/)  
+*Credit*: (c)2019 Directorate-General for the Territorial Development.
+
+Derived from 1129 common stations in the national geodetic network. 
+Residuals at 130 further test points average 0.09m, maximum 0.30m.
+Recommended to transform from Portuguese Lisbon Datum (EPSG:20790) to ETRS89 in Portugal (EPSG:3763).
+
+* DLx_ETRS89_geo.tif
+
+### Portugal: Datum 73 -> ETRS89
+
+Grid transformation from Portuguese Datum 73 to ETRS89 in Portugal.
+
+*Source*: [DGT](http://www.dgterritorio.pt/cartografia_e_geodesia/geodesia/transformacao_de_coordenadas/grelhas_em_ntv2/)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [Creative Commons Attribution 4.0](http://creativecommons.org/licenses/by/4.0/)  
+*Credit*: (c)2019 Directorate-General for the Territorial Development.
+
+Derived from 1129 common stations in the national geodetic network. 
+Residuals at 130 further test points average 0.06m, maximum 0.16m.
+Recommended to transform from Portuguese Datum 73 (EPSG:27493) to ETRS89 in Portugal (EPSG:3763).
+
+* D73_ETRS89_geo.tif
diff --git a/se_lantmateriet/.github/README.md b/se_lantmateriet/.github/README.md
new file mode 120000
index 0000000..3f35c37
--- /dev/null
+++ b/se_lantmateriet/.github/README.md
@@ -0,0 +1 @@
+../README.se_lantmateriet
\ No newline at end of file
diff --git a/se_lantmateriet/README.se_lantmateriet b/se_lantmateriet/README.se_lantmateriet
new file mode 100644
index 0000000..575b1bf
--- /dev/null
+++ b/se_lantmateriet/README.se_lantmateriet
@@ -0,0 +1,19 @@
+# README.se_landmateriet
+
+The files in this section result from the conversion of datasets originating
+from [Lantmäteriet](https://www.lantmateriet.se)
+
+## Included grids
+
+### Sweden: RH 2000 heights -> SWEREF 99 ellipsoidal heights
+
+*Source*: [Lantmäteriet](https://www.lantmateriet.se/en/maps-and-geographic-information/GPS-och-geodetisk-matning/Om-geodesi/Transformationer/Geoidmodeller/)  
+*Format*: GeoTIFF converted from GTX  
+*License*: [Creative commons, CC0](https://creativecommons.org/publicdomain/zero/1.0/)
+
+Vertical transformation for Geoid model SWEN17_RH2000. Used to make the
+transitions from heights above sea level in RH 2000 (EPSG:5613) to heights above the
+ellipsoid in SWEREF 99 (EPSG:4377). The RH 2000 height system is used on Swedish mainland, Öland
+and Gotland islands.
+
+* SWEN17_RH2000.tif
diff --git a/uk_os/.github/README.md b/uk_os/.github/README.md
new file mode 120000
index 0000000..e7f4e67
--- /dev/null
+++ b/uk_os/.github/README.md
@@ -0,0 +1 @@
+../README.uk_os
\ No newline at end of file
diff --git a/uk_os/README.uk_os b/uk_os/README.uk_os
new file mode 100644
index 0000000..101c87d
--- /dev/null
+++ b/uk_os/README.uk_os
@@ -0,0 +1,46 @@
+# README.uk_os
+
+The files in this section result from the conversion of datasets originating
+from [Ordnance Survey](https://www.ordnancesurvey.co.uk)
+
+## Included grids
+
+### Ireland: OSGM15 height, Malin head datum -> ETRS89 ellipsoidal heights
+
+*Source*: [Ordnance Survey](https://www.ordnancesurvey.co.uk/business-and-government/help-and-support/navigation-technology/os-net/formats-for-developers.html)  
+*Format*: GeoTIFF converted from GTX  
+*License*: [The 2-Clause BSD License](https://opensource.org/licenses/bsd-license.php)  
+
+Vertical transformation for Geoid model OSGM15, Malin head datum (EPSG:5731). Used in
+transformation from OSGM15 orthometric heights to WGS84/ETRS89 ellipsoidal heights.
+The Malin Head datum is used in the Republic of Ireland.
+
+* OSGM15_Malin.tif
+
+### Northern Ireland: OSGM15 height, Belfast height -> ETRS89 ellipsoidal heights
+
+*Source*: [Ordnance Survey](https://www.ordnancesurvey.co.uk/business-and-government/help-and-support/navigation-technology/os-net/formats-for-developers.html)  
+*Format*: GeoTIFF converted from GTX  
+*License*: [The 2-Clause BSD License](https://opensource.org/licenses/bsd-license.php)  
+
+Vertical transformation for Geoid model OSGM15, Belfast datum (EPSG:5732). Used in
+transformation from OSGM15 orthometric heights to WGS84/ETRS89 ellipsoidal heights.
+The Belfast datum is used in the Northern Ireland.
+
+* OSGM15_Belfast.tif
+
+### United Kingdom: OSGB36 -> ETRS89
+
+*Source*: [Ordnance Survey](https://www.ordnancesurvey.co.uk/business-and-government/help-and-support/navigation-technology/os-net/formats-for-developers.html)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [The 2-Clause BSD License](https://opensource.org/licenses/bsd-license.php)
+
+OSTN15 is the definitive OSGB36/ETRS89 transformation. OSTN15 in combination with the ETRS89
+coordinates of the OS Net stations, rather than the old triangulation network, define the National
+Grid. This means that, for example, the National Grid coordinates of an existing OSGB36 point,
+refixed using GNSS from OS Net and OSTN15, will be the correct ones. The original archived
+OSGB36 National Grid coordinates of the point (if different) will be wrong, by definition, but the
+two coordinates (new and archived) will agree on average to better than 0.1m (0.1m rmse, 68%
+probability).
+
+* OSTN15_NTv2_OSGBtoETRS.tif
diff --git a/us_nga/.github/README.md b/us_nga/.github/README.md
new file mode 120000
index 0000000..a728266
--- /dev/null
+++ b/us_nga/.github/README.md
@@ -0,0 +1 @@
+../README.us_nga
\ No newline at end of file
diff --git a/us_nga/README.us_nga b/us_nga/README.us_nga
new file mode 100644
index 0000000..5050916
--- /dev/null
+++ b/us_nga/README.us_nga
@@ -0,0 +1,30 @@
+# README.us_nga
+
+The files in this section result from the conversion of datasets originating
+from [US NGA](http://earth-info.nga.mil)
+
+## Included grids
+
+### Worldwide: EGM96 geoid model
+
+*Source*: [NGA](http://earth-info.nga.mil/GandG/wgs84/gravitymod/egm96/egm96.html)  
+*Format*: GeoTIFF converted from GTX  
+*License*: Public Domain  
+
+15 minute worldwide geoid undulation grid that transforms physical heights to WGS84 ellipsoidal heights.
+
+* egm96_15.tif
+
+### Vertical grid: EGM2008 geoid model
+
+*Source*: [NGA](http://earth-info.nga.mil/GandG/wgs84/gravitymod/egm2008/egm08_wgs84.html)  
+*Format*: GeoTIFF converted from GTX
+*License*: Public Domain
+
+2.5 minute worldwide geoid undulation grid that transforms physical heights to WGS84 ellipsoidal heights.
+
+This file has been produced by [GeographicLib](https://geographiclib.sourceforge.io/html/gravity.html)
+using the EGM2008 gravity model and can be regenerated with the
+[build_egm08_25_gtx.sh](https://raw.githubusercontent.com/OSGeo/proj-datumgrid/master/world/build_egm08_25_gtx.sh) script.
+
+* egm08_25.tif
diff --git a/us_noaa/.github/README.md b/us_noaa/.github/README.md
new file mode 120000
index 0000000..e6f8bcc
--- /dev/null
+++ b/us_noaa/.github/README.md
@@ -0,0 +1 @@
+../README.us_noaa
\ No newline at end of file
diff --git a/us_noaa/README.us_noaa b/us_noaa/README.us_noaa
new file mode 100644
index 0000000..a412a95
--- /dev/null
+++ b/us_noaa/README.us_noaa
@@ -0,0 +1,155 @@
+# README.us_nga
+
+The files in this section result from the conversion of datasets originating
+from [US NOAA](https://www.ngs.noaa.gov)
+
+## Included grids
+
+### USA: NAD83 -> NAD83 (HARN/HPGN)
+
+*Source*: [.los/.las files coming from NOAA](https://www.ngs.noaa.gov/PC_PROD/NADCON/NADCON.zip)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: Public Domain
+
+Grid data for high precision conversion of geographic coordinates from
+the original NAD83 (1986) (EPSG:4269) to NAD83 High Precision Geodetic Networks
+(HPGNs) (EPSG:4152), also referred to as High Accuracy Reference Networks (HARNs).
+NAD 83 coordinates based on the HPGN/HARN surveys changed approximately 0.2
+to 1.0 meter relative to the original NAD 83 (1986) adjustment.
+
+Those files have been converted to NTv2 grids with the
+[build_nad83_harn.sh](https://raw.githubusercontent.com/OSGeo/proj-datumgrid/master/north-america/build_nad83_harn.sh) script.
+
+* *hpgn.tif (51 files)
+
+### Continental USA VERTCON: NGVD (19)29 height to NAVD (19)88 height
+
+*Source*: converted from [NOAA VERTCON .94 grids](https://www.ngs.noaa.gov/PC_PROD/VERTCON/)  
+*Converter*: vertcon_94_to_gtx.py  
+*Format*: GeoTIFF converted from GTX  
+*License*: Public Domain
+
+Transform NGVD (19)29 height to NAVD (19)88 height. The .tif files contain
+the offset to add to NGVD 29 heights to get NAVD 88 heights.
+
+The horizontal grid coordinates may be referenced to NAD27 or NAD83
+
+* vertconc.tif
+* vertcone.tif
+* vertconw.tif
+
+### USA GEOID1999 model (superseded): NAVD88 height to NAD83
+
+*Source*: converted from [NOAA NGS .bin grids](https://geodesy.noaa.gov/GEOID/GEOID99/)  
+*Converter*: build_g1999.sh  
+*Format*: GeoTIFF converted from GTX  
+*License*: Public Domain
+
+The GEOID99 model is known as a hybrid geoid model, combining
+gravimetric information with GPS ellipsoid heights on leveled bench marks.
+The GEOID99 model was developed to support direct conversion between
+NAD 83 GPS ellipsoidal heights and NAVD 88 orthometric heights.
+
+It is superseded by later GEOIDxx models
+
+* g1999u01.tif to g1999u08.tif : Conterminous US
+* g1999a01.tif to g1999a04.tif : Alaska
+* g1999h01.tif : Hawaii
+* g1999p01.tif : Puerto Rico
+
+### USA GEOID2003 model (superseded): NAVD88 height to NAD83
+
+*Source*: converted from [NOAA NGS .bin grids](https://geodesy.noaa.gov/GEOID/GEOID03/)  
+*Converter*: build_g2003.sh  
+*Format*: GeoTIFF converted from GTX  
+*License*: Public Domain
+
+The GEOID03 model is known as a hybrid geoid model, combining
+gravimetric information with GPS ellipsoid heights on leveled bench marks.
+The GEOID03 model was developed to support direct conversion between
+NAD 83 GPS ellipsoidal heights and NAVD 88 orthometric heights.
+
+It is superseded by later GEOIDxx models
+
+* geoid03_conus.tif : Conterminous US
+* g2003a01.tif to g2003a04.tif : Alaska
+* g2003h01.tif : Hawaii
+* g2003p01.tif : Puerto Rico
+
+### USA GEOID2006 model (superseded): NAVD88 height to NAD83 (Alaska only)
+
+*Source*: converted from [NOAA NGS .bin grids](https://geodesy.noaa.gov/GEOID/GEOID06/)  
+*Converter*: build_g2006.sh  
+*Format*: GeoTIFF converted from GTX  
+*License*: Public Domain
+
+GEOID06 is a refined hybrid geoid model for Alaska only.
+
+GEOID06 converts between the U.S. ellipsoidal datum, NAD 83, and the U.S.
+vertical datum, NAVD 88. GEOID06 is built largely on the USGG2003 gravimetric geoid.
+
+It is superseded by later GEOIDxx models
+
+* geoid06_ak.tif : Alaska
+
+### USA GEOID2009 model (superseded): NAVD88/PRVD02/VIVD09/GUVD04 height to NAD83
+
+*Source*: converted from [NOAA NGS .bin grids](https://www.ngs.noaa.gov/GEOID/GEOID09/)  
+*Converter*: build_g2009.sh  
+*Format*: GeoTIFF converted from GTX  
+*License*: Public Domain
+
+The GEOID09 model is known as a hybrid geoid model, as it is modified
+from a gravimetric model to fit GPS ellipsoid heights on leveled bench marks.
+The GEOID09 model refers to a GRS-80 shaped ellipsoid,
+centered at the NAD83 origin.  It supports direct conversion between
+NAD83 GPS ellipsoidal heights and NAVD88, GUVD04 and ASVD03 orthometric heights,
+and will support future vertical datums PRVD02 nad VIVD09.
+
+* geoid09_conus.tif : Conterminous US.
+* geoid09_ak.tif : Alaska.
+* g2009h01.tif : Hawaii
+* g2009g01.tif : Guam and Northern Mariana Islands.
+* g2009s01.tif : American Samoa.
+* g2009p01.tif : Puerto Rico / U.S. Vigin Islands.
+
+### USA GEOID12B model (partial superseded): NAVD88/PRVD02/VIVD09/GUVD04/NMVD03/ASVD02 height to NAD83(2011)/NAD83(MA11)/NAD83(PA11)
+
+*Source*: converted from [NOAA NGS .bin grids](https://www.ngs.noaa.gov/GEOID/GEOID12B/)  
+*Converter*: build_g2012.sh  
+*Format*: GeoTIFF converted from GTX  
+*License*: Public Domain
+
+GEOID12B is a hybrid geoid height model that can transform between the relevant
+vertical datum for each region to a NAD 83 ellipsoid height
+See https://www.ngs.noaa.gov/GEOID/GEOID12B/faq_2012B.shtml for more details.
+
+* g2012bu0.tif : Conterminous US, referenced to NAD83(2011). Vertical datum: NAVD88
+* g2012ba0.tif : Alaska, referenced to NAD83(2011). Vertical datum: NAVD88
+* g2012bh0.tif : Hawaii, referenced to NAD83(PA11). Vertical datum: identical to that of USGG2012, which is offset by 50-60 cm from some Local Tidal bench mark values. 
+* g2012bg0.tif : Guam and Northern Mariana Islands, referenced to NAD83(PA11). Vertical datum: GUVD04/NMVD03
+* g2012bs0.tif : American Samoa, referenced to NAD83 (PA11). Vertical datum: ASVD02
+* g2012bp0.tif : Puerto Rico / U.S. Vigin Islands, referenced to NAD83(2011). Vertical datum: PRVD02 and VIVD09
+
+The g2012bu0.tif and g2012bp0.tif grids are superseded by the
+g2018p0.tif and g2018p0.tif grids of GEOID18.
+
+### USA GEOID18 model: NAVD88/PRVD02 height to NAD83(2011)
+
+*Source*: converted from [NOAA NGS .bin grids](https://www.ngs.noaa.gov/GEOID/GEOID18/)  
+*Converter*: build_g2018.sh  
+*Format*: GeoTIFF converted from GTX  
+*License*: Public Domain
+
+GEOID18 is intended for use with coordinates in the North American Datum of 1983 (2011)
+[NAD 83 (2011) epoch 2010.00]. It provides orthometric heights consistent with the
+North American Vertical Datum of 1988 (NAVD 88), the Puerto Rico Vertical Datum of
+2002 (PRVD02), or the Virgin Islands Vertical Datum of 2009 (VIVD09).
+
+GEOID18 covers CONUS, Puerto Rico, and the U.S. Virgin Islands and supersedes
+GEOID12B in these regions. GEOID18 does NOT cover Alaska, Hawaii, Guam and the
+Commonwealth of the Northern Mariana Islands (CNMI) where users should continue
+to use GEOID12B.
+
+* g2018u0.tif : Conterminous US, referenced to NAD83(2011). Vertical datum: NAVD88
+* g2018p0.tif : Puerto Rico / U.S. Vigin Islands, referenced to NAD83(2011). Vertical datum: PRVD02 and VIVD09
diff --git a/us_usgs/.github/README.md b/us_usgs/.github/README.md
new file mode 120000
index 0000000..50d9990
--- /dev/null
+++ b/us_usgs/.github/README.md
@@ -0,0 +1 @@
+../README.us_usgs
\ No newline at end of file
diff --git a/us_usgs/README.us_usgs b/us_usgs/README.us_usgs
new file mode 100644
index 0000000..6de016e
--- /dev/null
+++ b/us_usgs/README.us_usgs
@@ -0,0 +1,41 @@
+# README.us_usgs
+
+The files in this section result from the conversion of datasets originating
+from USGS
+
+TODO: Aren't they coming from NOAA instead ?
+
+## Included grids
+
+### USA: NAD27 -> NAD83
+
+*Source*: USGS  
+*Format*: GeoTIFF converted from CTable2  
+*License*: Public Domain
+
+* alaska.tif - Alaska
+* conus.tif - Conterminous U.S.
+* hawaii.tif - Hawaii
+* prvi.tif - Puerto Rico, Virgin Is.
+* stgeorge.tif - St. George Is, Alaska
+* stlrnc.tif - St. Lawrence Is., Alaska
+* stpaul.tif - St. Paul Is., Alaska
+
+### USA: NAD83 -> NAD83 (HARN/HPGN)
+
+*Source*: USGS
+*Format*: GeoTIFF converted from CTable2
+*License*: Public Domain
+
+Grid data for high precision conversion of geographic coordinates from
+the original NAD83 (1986) (EPSG:4269) to NAD83 High Precision Geodetic Networks
+(HPGNs) (EPSG:4152), also referred to as High Accuracy Reference Networks (HARNs).
+NAD 83 coordinates based on the HPGN/HARN surveys changed approximately 0.2
+to 1.0 meter relative to the original NAD 83 (1986) adjustment.
+
+* FL.tif - Florida
+* MD.tif - Maryland
+* TN.tif - Tennessee
+* WI.tif - Wisconsin
+* WO.tif - Washington, Oregon, N. California
+