Concatenated operation with height reversal fails

[barry-gallagher]

Example of problem

Using the attached proj.db including custom NOAA tidal CRS and transform records

projinfo --hide-ballpark -s EPSG:8542 -t NOAA:8509 --spatial-test intersects
createOperations() failed with: cannot build transformation NOAA:14434: Inconsistent chaining of CRS in operations

Problem description

The concatenated_operation 14434 is supposed to perform these steps:

• EPSG:9168 -- NAD83(FBN) 3D to NAD83(FBN)+NAVD88 height
• EPSG:7989 -- NAVD88 height to NAVD88 depth
• NOAA:11492 -- NAD83(FBN)+LMSL to NAD83(FBN)+NAVD88 depth
• NOAA:11490 -- NAD83(FBN)+MLLW to NAD83(FBN)+LMSL

In the function ConcatenatedOperation::fixStepsDirection the second step is recognized as a conversion and then assumes the target of the first operation is the same as the source of the third operation, rather than checking if the third operation needs an op->inverse() like the rest of the function does.

If I reverse the source and target of the NOAA:11492 operation then the call results in my expected output below.

Expected Output

Candidate operations found: 1
-------------------------------------
Operation No. 1:

NOAA:14434, Inverse of 'Inverse of 'NAD83(FBN) to NAD83(FBN) + MLLW (WAjuandefuca01/vdatum_3.4_20141224/1983-2001) depth'', 0.1 m, 17203 Washington - Strait of Juan de Fuca Local Mean Sea Level 1983-2001

PROJ string:
+proj=pipeline
  +step +proj=axisswap +order=2,1
  +step +proj=unitconvert +xy_in=deg +xy_out=rad
  +step +inv +proj=vgridshift +grids=us_noaa_geoid03_conus.tif +multiplier=1
  +step +proj=unitconvert +xy_in=rad +xy_out=deg
  +step +proj=axisswap +order=2,1
  +step +proj=axisswap +order=1,2,-3
  +step +proj=axisswap +order=2,1
  +step +proj=unitconvert +xy_in=deg +xy_out=rad
  +step +inv +proj=vgridshift
        +grids=us_noaa_nos_NAD83(FBN)_LMSL_NAVD88_(WAjuandefuca01_vdatum_3.4_20141224_1983-2001).tif
        +multiplier=1
  +step +proj=axisswap +order=1,2,-3
  +step +proj=axisswap +order=1,2,-3
  +step +proj=vgridshift
        +grids=us_noaa_nos_NAD83(FBN)_MLLW_LMSL_(WAjuandefuca01_vdatum_3.4_20141224_1983-2001).tif
        +multiplier=1
  +step +proj=unitconvert +xy_in=rad +xy_out=deg
  +step +proj=axisswap +order=2,1

Environment Information

• PROJ version 9.4 (and 9.3.1)
• Operation System Information - Windows 11

Installation method

• conda
  proj.zip

[rouault]

Fix for the specific issue of solving the inconsistent chaining in #4120 . However the resulting pipeline is likely wrong because of #4118

[barry-gallagher]

Thanks @rouault for the quick fix!