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I could use help getting FME 2019.0 properly set to transform data from Canadian vertical datum 1928 to 2013.

My starting points are https://knowledge.safe.com/questions/99317/adding-vertical-coordinate-systems-to-fme.html and https://knowledge.safe.com/articles/29325/creating-vertical-adjustment-grid-files-for-use-wi.html.

From Safe I have downloaded and installed the extra Reprojection Grid Files.

From NRCAN I have downloaded the 8 archives from Geoid Models, and unpacked to `C:\local\geo_grid_shift_files`.

I see 8 .byn files:

# CGVD2013

 

CGG2013ai08.byn        

 

CGG2013an83.byn

# CGVD28

 

HT2_1997.byn            

 

HT2_2002v70.byn

 

HT2_2010v70.byn

# 1928 to 2013 conversion

 

HT2_1997_CGG2013a.byn

 

HT2_2002v70_CGG2013a.byn

 

HT2_2010v70_CGG2013a.byn

3 of these are already present in FME Reproject folder tree

  • CGG2013a - CSRS and ITRF versions (CGG2013n83 & CGG2013i08 respectively) 
  • HT2_1997 - FME has it, though using the old name of HT2_0 according to a note on GPS-H page (ref).

 

I understand the next step is to create .gdc files that tell FME where the .byn files live, and where my confusion grows. 

Creating Vertical Adjustment Grid files for use with FME says multiple grid files can be referred to in one .gdc, but at all the example ones I see under `Reproject\GeoidHeightGrids\Canada` are one to one. Do I put all HT2_yyyy*.byn files in a single cgvd28_to_cgvd2013.gdc file or continue the 1:1 relationship?

I'm also not sure what the naming convention represents. What do the parts in  "CGG2010-NAD83CSRS_CGVD2010.gdc" mean? The internal comment indicates we are starting from GRS80 and outputting CGVD2010, but the filename starts and ends with 2010.

# GRS80 Ellipsoid height -> CGVD2010
# Reference Frame: NAD83CSRS (according to GPS-H 3.11 Model Information window)
# http://www.geod.nrcan.gc.ca/hm/public_model_e.php
../../GridData/Canada/Geoids/CGG2010n.byn

 

Finally, after the above is sorted out, what's the proper way to use it? It would be helpful to see a complete workbench workspace, does anyone have a portable/simple example they can share?

 

Thanks!

@tforward, @daveatsafe

Hi @maphew,

The .gdc file is meant to be a catalog of all the files that may be used for a particular transformation.

Sometime a large grid is been divided into multiple files (ie. USA - Geoid99-Nad83_Navd88-1999). In this case, the .gdc file will contain the locations of all the files for that grid.

Most of the time, however, there is only a single grid file, and then the .gdc file will have only a single entry.

For the NRCAN file, it appears that each file is a different transformation, and so each would need a corresponding .gdc file.

The .gdc file is what you choose in the CsmapReprojector for the Geoid Height Grid.

Hi @maphew,

The .gdc file is meant to be a catalog of all the files that may be used for a particular transformation. 

Sometime a large grid is been divided into multiple files (ie. USA - Geoid99-Nad83_Navd88-1999). In this case, the .gdc file will contain the locations of all the files for that grid.

Most of the time, however, there is only a single grid file, and then the .gdc file will have only a single entry. 

For the NRCAN file, it appears that each file is a different transformation, and so each would need a corresponding .gdc file.

The .gdc file is what you choose in the CsmapReprojector for the Geoid Height Grid.

So like this?

Assign 1928 - cgvd28-1997.gdc:

# GRS80 Ellipsoid height -> CGVD28 (1997)
# Reference Frame:
# https://webapp.geod.nrcan.gc.ca/geod/data-donnees/geoid.php?locale=en
# https://knowledge.safe.com/questions/102610/proper-setup-to-convert-canada-vertical-datum-cgvd.html
../path/to/HT2_1997.byn

Convert from 1928 to 2013 - cgvd28-1997_to_cgvd2013a.gdc:

# HTv2.0 1997 (CGVD28) -> CGG2013a
# Reference Frame:
# https://webapp.geod.nrcan.gc.ca/geod/data-donnees/geoid.php?locale=en
# https://knowledge.safe.com/questions/102610/proper-setup-to-convert-canada-vertical-datum-cgvd.html
../path/to/HT2_1997_CGG2013a.byn

 

To be consistent with FME doc format, what should be put in 'Reference Frame:'?

 

 

 

 

So like this?

Assign 1928 - cgvd28-1997.gdc:

# GRS80 Ellipsoid height -> CGVD28 (1997)
# Reference Frame:
# https://webapp.geod.nrcan.gc.ca/geod/data-donnees/geoid.php?locale=en
# https://knowledge.safe.com/questions/102610/proper-setup-to-convert-canada-vertical-datum-cgvd.html
../path/to/HT2_1997.byn

Convert from 1928 to 2013 - cgvd28-1997_to_cgvd2013a.gdc:

# HTv2.0 1997 (CGVD28) -> CGG2013a
# Reference Frame:
# https://webapp.geod.nrcan.gc.ca/geod/data-donnees/geoid.php?locale=en
# https://knowledge.safe.com/questions/102610/proper-setup-to-convert-canada-vertical-datum-cgvd.html
../path/to/HT2_1997_CGG2013a.byn

 

To be consistent with FME doc format, what should be put in 'Reference Frame:'?

 

 

 

 

Lines beginning with '#' are comments, so you only need to specify the Reference Frame if it means something to you.

Lines beginning with '#' are comments, so you only need to specify the Reference Frame if it means something to you.

That was my confused way of asking "What does the 'Reference Frame' comment mean to Safe?". ;-)

Is alright, I seem to have something that works now. Thanks for the assistance.

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