Changed default for ASCII_DAT time TIMEUNITS between QGIS 3.8 and QGIS 3.10.1

[saberraz]

Latest MDAL parses time for hydro_as-2d incorrectly. The upper image is the latest MDAL and the one in the bottom is the correct time (MDAL shipped with QGIS 3.8).

[PeterPetrik]

@saberraz missing one of the two pictures.

[saberraz]

updated the OP.

[PeterPetrik]

This one is tricky, let me explain the situation

| QGIS | MDAL | TIMEUNITS | Default | link 

|---------|--------|------|-----------|
| 2.x     |  N/A   | No   | Seconds   
| 3.8.    | 0.3.3  | No   | Seconds   
| 3.10.0  | 0.3.3  | No   | Seconds
| 3.10.0  | 0.4.0  | Yes  | Hours
| 3.12.x  | 0.5.x  | Yes  | ?

old crayfish implementation https://github.com/lutraconsulting/qgis-crayfish-plugin/blob/7ad50a456dfb5d9340cf0dd60bbfdfe9b6d0eb2c/corelib/frmts/crayfish_dataset_dat.cpp#L513

PR that changed default: https://github.com/lutraconsulting/MDAL/commit/bf638c19c92a1e0dea91f6b942dc97b84352ee54#diff-6a5b644e181ca35770ef3dbeea8d4dc2L323

TIMEUNITS support: https://github.com/lutraconsulting/MDAL/blob/1aa79d395c4f107eb1586010d72c3fd4dd9f18d3/mdal/frmts/mdal_ascii_dat.cpp#L455

This issue is that ASCII_DAT is used by BASEMENT, HYDRO_AS-2D and TUFLOW solvers, with each different default HYDRO_AS-2D: Seconds TUFLOW: Hours

Standard does not define the default units at all, see https://www.xmswiki.com/wiki/SMS:ASCII_Dataset_Files_*.dat , but recommends to use TIMEUNITS flag to specify it. So either seconds or hours as default is compliant with standard.

So the clean solution is to add this line at the line before definition of first timestep data (TS flag)

TIMEUNITS Seconds 
TIMEUNITS Hours

In QGIS 3.12 hopefully we will have https://github.com/qgis/QGIS/issues/33196 implemented so user can tweak such problems

[PeterPetrik]

@saberraz @wonder-sk any suggestion if close this as "won't fix" (default hours) or get back to seconds default?

[BenediktRotheOnGITHub]

This is Benedikt Rothe from Hydrotec - the developers of HYDRO_AS-2D. We will add "TIMEUNITS Seconds" to dat-files in our next major-release.

[BenediktRotheOnGITHub]

We added TIMEUNITS to the dat-files in HYDRO_AS-2d. Unfortunately MDAL (QGIS 3.10) does not evaluate this, since the datasets are the "old format" (MDAL::DriverAsciiDat::loadOldFormat).

We'd prefere not to switch to the "new format", since lot's of customers have code to read these files and we don't want to break there code.

Would Lutraconsult evaluate timeunits for old format too?

Regards, Benedikt

[PeterPetrik]

@BenesName it should be possible to implement, created issue https://github.com/lutraconsulting/MDAL/issues/196

[PeterPetrik]

released 0.4.1 for QGIS 3.10.2 that should keep the default to hours. But also it adds option to specify TIMEUNITS manually for both old&new formats. So to change your dataset, manually add TIMEUNITS to the input format. https://github.com/qgis/QGIS/pull/33687

From QGIS 3.12+, the QGIS GUI has option to override the TIMEUNITS (in case or incorrectly parsed by MDAL)