template_t failure (geoTiffSRSTest) when PROJ datum grids are installed

[lpechacek]

FWIW, template_t test fails on openSUSE Tumbleweed 20251110 (rolling distro with proj-9.7.0, gdal-3.11.3, gcc-15, libQt5Core5-5.15.18+kde109). The failure stems from a discrepancy between calculated and expected coordinates in the British National Grid (EPSG 27700). The test can be "fixed" by removing the datum grids (uninstall package that holds uk_os_OSTN15_NTv2_OSGBtoETRS.tif file).

I don't understand the very details of the datum grid corrections, so I'm not proposing any kind of fix here. Just saying that the test success depends on the system configuration.

Failure case

lpechacek@fmn:~> /data/build/build-oomapper-Desktop-Debug/test/template_t geoTiffSRSTest
Warning: Ignoring XDG_SESSION_TYPE=wayland on Gnome. Use QT_QPA_PLATFORM=wayland to run on Wayland anyway.
********* Start testing of TemplateTest *********
Config: Using QtTest library 5.15.18, Qt 5.15.18 (x86_64-little_endian-lp64 shared (dynamic) release build; by GCC 15.2.1 20251006), opensuse-tumbleweed 20251110
PASS   : TemplateTest::initTestCase()
QDEBUG : TemplateTest::geoTiffSRSTest() GdalTemplate: Using GDAL driver 'GTiff'
QDEBUG : TemplateTest::geoTiffSRSTest() GdalTemplate raster bands: RedByte, GreenByte, BlueByte, AlphaByte
FAIL!  : TemplateTest::geoTiffSRSTest() Compared values are not the same
   Actual   (projected): QPointF(310000,518999)
   Expected (expected) : QPointF(310000,519000)
   Loc: [/data/src/oomapper/test/template_t.cpp(406)]
PASS   : TemplateTest::cleanupTestCase()
Totals: 2 passed, 1 failed, 0 skipped, 0 blacklisted, 132ms
********* Finished testing of TemplateTest *********

Success case

lpechacek@fmn:~> sudo rpm -e proj-data-uk
lpechacek@fmn:~> /data/build/build-oomapper-Desktop-Debug/test/template_t geoTiffSRSTest
Warning: Ignoring XDG_SESSION_TYPE=wayland on Gnome. Use QT_QPA_PLATFORM=wayland to run on Wayland anyway.
********* Start testing of TemplateTest *********
Config: Using QtTest library 5.15.18, Qt 5.15.18 (x86_64-little_endian-lp64 shared (dynamic) release build; by GCC 15.2.1 20251006), opensuse-tumbleweed 20251110
PASS   : TemplateTest::initTestCase()
QDEBUG : TemplateTest::geoTiffSRSTest() GdalTemplate: Using GDAL driver 'GTiff'
QDEBUG : TemplateTest::geoTiffSRSTest() GdalTemplate raster bands: RedByte, GreenByte, BlueByte, AlphaByte
PASS   : TemplateTest::geoTiffSRSTest()
PASS   : TemplateTest::cleanupTestCase()
Totals: 3 passed, 0 failed, 0 skipped, 0 blacklisted, 123ms
********* Finished testing of TemplateTest *********
lpechacek@fmn:~> 

Raw coordinate calculation with PROJ (excludes all the intermediate components - Mapper, Qt, compiler, ...)

lpechacek@fmn:~> echo 54.558203 -3.393209 | cs2cs -f '%.2f' 'epsg:4326' 'epsg:27700'
310000.25	518999.15 0.00
lpechacek@fmn:~> sudo rpm -e proj-data-uk
lpechacek@fmn:~> echo 54.558203 -3.393209 | cs2cs -f '%.2f' 'epsg:4326' 'epsg:27700'
310000.01	519000.02 0.00