GetNoDataValue returning wrong value

[jontwo]

Expected behavior and actual behavior.

When upgrading a Python application to GDAL 3.4.1, a test was failing due to GetNoDataValue returning a different value to previous versions.

Steps to reproduce the problem.

test_data.tar.gz
Using the following Python code, the nodata value returned at GDAL 3.3.3 is -999.0 and at GDAL 3.4.1 it is -3.4028234663852886e+38

    ds = gdal.OpenEx('test_input_1.tif)
    print(ds.GetRasterBand(1).GetNoDataValue())

Operating system

Rocky Linux 8.5
Linux version 4.18.0-348.12.2.el8_5.x86_64 (mockbuild@dal1-prod-builder001.bld.equ.rockylinux.org) (gcc version 8.5.0 20210514 (Red Hat 8.5.0-3) (GCC)) #1 SMP Wed Jan 19 17:53:40 UTC 2022

GDAL version and provenance

Wheel build based on the recipe at https://github.com/sgillies/frs-wheel-builds

Versions:
https://download.osgeo.org/libtiff/tiff-4.3.0.tar.gz
http://download.osgeo.org/geos/geos-3.10.0.tar.bz2
http://download.osgeo.org/proj/proj-8.1.1.tar.gz
http://download.osgeo.org/gdal/3.4.1/gdal-3.4.1.tar.gz

Options:
./configure
--with-threads
--disable-debug
--disable-static
--without-grass
--without-libgrass
--without-jpeg12
--with-libtiff
--with-jpeg
--with-gif
--with-png
--with-webp
--with-geotiff=internal
--with-sqlite3=/usr
--with-spatialite
--with-pcraster=internal
--with-pcidsk=internal
--with-pam
--with-geos=/usr/local/bin/geos-config
--with-proj=/usr/local
--with-expat=/usr/local
--with-libjson-c
--with-libiconv-prefix=/usr
--with-libz=/usr
--with-curl=/usr/local/bin/curl-config
--with-netcdf=/usr/local/netcdf
--with-openjpeg
--without-python
--without-hdf4
--without-hdf5
--with-fgdb=/usr/local/src/FileGDB_API-64
--with-pg=yes
--disable-driver-elastic \

[rouault]

I get the correct result -999 with the current state of the GDAL 3.4 branch / 3.4.2, and I've no reason to believe it to be different with 3.4.1
Perhaps you have also a test_input_1.tif.aux.xml file that overrides the nodata value ?

[jontwo]

I do - I thought it only contained the stats so ignored it, but it does contain the line

<NoDataValue le_hex_equiv="000000E0FFFFEFC7">-3.40282346638529E+38</NoDataValue>

Is this ignored at v3.3.3?

[jratike80]

Could you please annex also the aux.xml file?

[rouault]

Is this ignored at v3.3.3?

yes, support for reading nodata value from aux.xml is a 3.4.1 bugfix

[jontwo]

test_aux_xml.tar.gz
Thanks for your help, I have this working now.