Question

Unable to use geoid height grid for vertical transformation

caracadrian
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I am trying to add a custom transformation from Romanian national projection to WGS84.

I have added the .gsb file and the XFORM_DEF to MyCoordSysDefs.fme and the horizontal transformation works with CSMapReprojector.

I tried adding a Vertical transformation but I keep getting the error:

Couldn't open file named C:\\Program Files\\FME\\Reproject\\GeoidHeightGrids\\World\\..\\..\\GridData\\WW15MGH.GRD.

CS-MAP Reprojector: Unable to load geoid height grid 'C:\\Program Files\\FME/Reproject\\GeoidHeightGrids\\World\\Egm96-Wgs84.gdc'

Reprojector: Could not create reprojection engine

I tried a custom GRD file and that doesn't work either. The same error:

Couldn't open file named C:\\Program Files\\FME\\Reproject\\GeoidHeightGrids\\Romania\\..\\..\\GridData\\Romania\\EGG97_QGR.grd.

CS-MAP Reprojector: Unable to load geoid height grid 'C:\\Program Files\\FME/Reproject\\GeoidHeightGrids\\Romania\\EGM96_QGR1.gdc'

Reprojector: Could not create reprojection engine

I tried using the vertical shift in both ways (Orto to elipsoid and elipsoid to orto) with no success.

Please help.

12 replies

daveatsafe
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Hi @caracadrian,

In order to keep our installer to a reasonable size, we provide the vertical grids as a separate download, which can be found on our Download page, under the heading Reprojection Grid Files.

Please download and install these files in order to use the Egm96-Wgs84 vertical transformation.

For the custom grid file to work with FME, it must be in the format described here. If you would like to share the file, or post a source for it, I would be happy to take a look at it to see if it will work in FME, or can be converted to a form that will work. If you do not want to make the file public, you can send it to me at dave.campanas@safe.com.

caracadrian
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Badge +20

Downloading and installing geoids didn't help.

Couldn't open file named C:\\Program Files\\FME\\Reproject\\GeoidHeightGrids\\World\\..\\..\\GridData\\WW15MGH.GRD.

CS-MAP Reprojector: Unable to load geoid height grid 'C:\\Program Files\\FME/Reproject\\GeoidHeightGrids\\World\\Egm96-Wgs84.gdc'

Reprojector: Could not create reprojection engine

I used the instructions from https://knowledge.safe.com/articles/29325/creating-vertical-adjustment-grid-files-for-use-wi.html" target="_blank">Here to create my custom .grd file making 2 small modifications to reach the input precision (annotated in 3269-convert-ascii-points-to-grd v3.fmw).

EGG97_QGR.grd is the custom grid I created

EGG97_QGR.GRT is the source data I used to create the input ascii file RO_Grid_input.txt.

EGG97_QGRJ.GRD is the official geoid grid - I can't figure out how to use it. (it has the J in its name, not to be confused with MY custom grid).

EGM96_QGR.gdc is the catalog file that routes to the grid.

I zip'd everything: ro-grid.zip

caracadrian
Rank
Badge +20

Downloading and installing geoids didn't help.

Couldn't open file named C:\\Program Files\\FME\\Reproject\\GeoidHeightGrids\\World\\..\\..\\GridData\\WW15MGH.GRD.

CS-MAP Reprojector: Unable to load geoid height grid 'C:\\Program Files\\FME/Reproject\\GeoidHeightGrids\\World\\Egm96-Wgs84.gdc'

Reprojector: Could not create reprojection engine

I used the instructions from https://knowledge.safe.com/articles/29325/creating-vertical-adjustment-grid-files-for-use-wi.html" target="_blank">Here to create my custom .grd file making 2 small modifications to reach the input precision (annotated in 3269-convert-ascii-points-to-grd v3.fmw).

EGG97_QGR.grd is the custom grid I created

EGG97_QGR.GRT is the source data I used to create the input ascii file RO_Grid_input.txt.

EGG97_QGRJ.GRD is the official geoid grid - I can't figure out how to use it. (it has the J in its name, not to be confused with MY custom grid).

EGM96_QGR.gdc is the catalog file that routes to the grid.

I zip'd everything: ro-grid.zip

Also, I already had WW15MGH.GRD from somewhere else and it looked ok and it's identical to the one from the Safe download page. I used it in other software and it worked. I didn't have the .96 file but I don't think it's used.

 

 

caracadrian
Rank
Badge +20

Hi @caracadrian,

In order to keep our installer to a reasonable size, we provide the vertical grids as a separate download, which can be found on our Download page, under the heading Reprojection Grid Files.

Please download and install these files in order to use the Egm96-Wgs84 vertical transformation.

For the custom grid file to work with FME, it must be in the format described here. If you would like to share the file, or post a source for it, I would be happy to take a look at it to see if it will work in FME, or can be converted to a form that will work. If you do not want to make the file public, you can send it to me at dave.campanas@safe.com.

@DaveAtSafe did you have a look at the files I uploaded? Is there any hope for me?
A
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Hi @DaveAtSafe I am trying to download a geoid height grid to convert from WGS84 heights to OS Newlyn Level heights (UK OSGB36 datum). But I can't find the grid in the 'World' folder in 'C:\\Program Files (x86)\\FME\\Reproject\\GeoidHeightGrids' or in the FME Download page. Do you know where I can find this grid?

I need to use FME 2016..

Thank you in advance.

daveatsafe
Rank
Userlevel 2
Badge +17

Hi @DaveAtSafe I am trying to download a geoid height grid to convert from WGS84 heights to OS Newlyn Level heights (UK OSGB36 datum). But I can't find the grid in the 'World' folder in 'C:\\Program Files (x86)\\FME\\Reproject\\GeoidHeightGrids' or in the FME Download page. Do you know where I can find this grid?

I need to use FME 2016..

Thank you in advance.

Hi @aquamarine,

 

I'm sorry, but the OSGM15 vertical grid is not included in the FME supplied grids. However, this vertical adjustment can be done by the GridInquestIIReprojector, which was added in FME 2017.1.

 

Earlier versions of FME included the GridInquestReprojector, but this can only do the vertical transformation to OSGM02.

 

A
Badge +1
Hi @aquamarine,

 

I'm sorry, but the OSGM15 vertical grid is not included in the FME supplied grids. However, this vertical adjustment can be done by the GridInquestIIReprojector, which was added in FME 2017.1.

 

Earlier versions of FME included the GridInquestReprojector, but this can only do the vertical transformation to OSGM02.

 

Hi @DaveAtSafe

 

 

Thanks for your advice.

 

 

I have tried GridInquestIIReprojector as you recommended but I'm still having trouble.

 

 

GridInquestII does not have WGS84 as an option for the 'Source Coordinate System'. Therefore I first converted the WGS84 coords to ETRS89 using CSMapAttributeReprojector and then from ETRS89 to OSGB36/British National Grid using GridInquestIIReprojector. However the resultant height value doesn't seem to be correct. I didn't set the 'Vertical Datum' as it says in brackets "Irish Systems only" and my projection is for England.

 

 

Please see the screenshot of my workbench.

 

 

Am I taking the correct approach?

 

Thank you

 

reprojections.png

 

daveatsafe
Rank
Userlevel 2
Badge +17
Hi @DaveAtSafe

 

 

Thanks for your advice.

 

 

I have tried GridInquestIIReprojector as you recommended but I'm still having trouble.

 

 

GridInquestII does not have WGS84 as an option for the 'Source Coordinate System'. Therefore I first converted the WGS84 coords to ETRS89 using CSMapAttributeReprojector and then from ETRS89 to OSGB36/British National Grid using GridInquestIIReprojector. However the resultant height value doesn't seem to be correct. I didn't set the 'Vertical Datum' as it says in brackets "Irish Systems only" and my projection is for England.

 

 

Please see the screenshot of my workbench.

 

 

Am I taking the correct approach?

 

Thank you

 

reprojections.png

 

Hi @aquamarine,

 

You can skip the CsmapReprojector - FME considers WGS84 and ETRS89 as equivalent, so no transformation is being done there.

 

I think there is only a single vertical datum for England, which is automatically applied, so no choice is required for that parameter.

 

Have you tried setting the Destination coordinate system version to 2015? I think that is the most current datum.

 

A
Badge +1
Hi @aquamarine,

 

You can skip the CsmapReprojector - FME considers WGS84 and ETRS89 as equivalent, so no transformation is being done there.

 

I think there is only a single vertical datum for England, which is automatically applied, so no choice is required for that parameter.

 

Have you tried setting the Destination coordinate system version to 2015? I think that is the most current datum.

 

Great thanks @DaveAtSafe

 

I didn't realize the two projections were considered equivalent. I have tried your method and the height still looks wrong but I now believe that it must be an error with the input height value rather than the FME workflow.

 

Thanks again.

 

D

Hi @daveatsafe

I have tried to create the grd file from the 3269-convert-ascii-points-to-grd.fmw but the grid file created doesn't seem to work in FME. It looks to be in the same format as WW15MGH.GRD but I did notice that this file is no longer included in the fme-grids-b19238.zip download.

How do I get a custom Geoid model to work?

Thanks,

Dushan

daveatsafe
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Userlevel 2
Badge +17

Hi @daveatsafe

I have tried to create the grd file from the 3269-convert-ascii-points-to-grd.fmw but the grid file created doesn't seem to work in FME. It looks to be in the same format as WW15MGH.GRD but I did notice that this file is no longer included in the fme-grids-b19238.zip download.

How do I get a custom Geoid model to work?

Thanks,

Dushan

Hi @darumugam,

The WW15MGH grid is included in the Reprojection Grid files download that can be found on our download page. This package includes all the less-used grid data, in order to keep our installer at a reasonable size.

FME will sometimes fail the first time it uses a custom grid, due the compiling of the grid to a binary ._96 file. However, it should work with all subsequent runs. If it continues to fail, please send me a copy of the grid: and I will see if I can find the reason for the failure.

caracadrian
Rank
Badge +20

Hi @daveatsafe

I have tried to create the grd file from the 3269-convert-ascii-points-to-grd.fmw but the grid file created doesn't seem to work in FME. It looks to be in the same format as WW15MGH.GRD but I did notice that this file is no longer included in the fme-grids-b19238.zip download.

How do I get a custom Geoid model to work?

Thanks,

Dushan

@darumugam the first time you use the custom .grd file you have to run FME As Administrator in order to compile it to ._96 format.

The thing is, FME doesn't really use the .grd file. It compiles it at the first run to binary ._96. If you put your .grd file in C:\\Program Files\\FME\\Reproject\\GridData\\ , FME will not be able to do the compiling unless it runs as administrator because normal users don't have write access to Program Files.

Hope this helps

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