Problem with Bathymetry_Converter when using files other than tutorial-provided files (GDAL Error and ValueError)

[smtbhd32]

Hi @woensug-choi,
I tried using the Bathymetry_Converter tool to convert custom bathymetry .tif files (downloaded from GEBCO and other sources) into a model usable for Gazebo simulation.

# Bathymetry Converter - automation script
###################################################################
PREFIX = 'MontereyBay'
SOURCE = 'bathymetry_source/gebco4.tif'

# Flag for single tile generation
ONE_TILE_AT_ORIGIN = True
# Mesh simplification level (0 ~ 3)
SIMPLIFICATION_LEVEL = 0

# Range
STARTLON = 84.8041667
STARTLAT = 8.5250000
ENDLON = 88.6250000
ENDLAT = 12.5041667

# Resolution
DLON = 0.004166666666667
DLAT = 0.004166666666667
OVERLON = 0.0005
OVERLAT = 0.0005
###################################################################

However, when using files other than the example ones provided in the tutorial, I encountered the following error during the conversion process:

ERROR 1: Ungridded dataset: At line 92, Y spacing was 469.489210. Expected 469.018320
  0%|                                                     | 0/1 [00:13<?, ?it/s]
Traceback (most recent call last):
  File "/home/mkbathy/workdir/mkbathy.py", line 155, in <module>
    gdal.Translate(filename + '.tif', filename + '.asc', options='-of GTiff -a_srs EPSG:3857')
  File "/opt/conda/envs/mkbathy/lib/python3.10/site-packages/osgeo/gdal.py", line 491, in Translate
    return TranslateInternal(destName, srcDS, opts, callback, callback_data)
  File "/opt/conda/envs/mkbathy/lib/python3.10/site-packages/osgeo/gdal.py", line 4674, in TranslateInternal
    return _gdal.TranslateInternal(*args)
ValueError: Received a NULL pointer.

Steps to Reproduce

1. Use a .tif bathymetry file from GEBCO (or other non-tutorial sources).
2. Attempt to convert using Bathymetry_Converter.
3. Encounter GDAL error and crash.

Additional Information

• The files provided with the tutorial (for example, Monterey Bay) work fine.
• Other .tif files, trigger the above errors.
• I am using:
  • Ubuntu 22.04
  • GDAL installed
  • ROS 2 Humble
  • Gazebo Harmonic

Request

Could you please guide if:

• There are any pre-processing steps required for the .tif files before feeding them to Bathymetry_Converter?
• Or if the tool currently expects a specific formatting or spacing of the raster grids?

Also, if helpful, I am attaching the .tif file here that causes the issue:
Gebco TIF File Link
Noaa TIF File Link

Thank you for this tool! Looking forward to your response.

[woensug-choi]

@smtbhd32 It's been quite some time since I've had hand on this tool. Preliminary suspect would be that the TIF files you are trying with doesn't have information of srs (https://gdal.org/en/stable/programs/gdalsrsinfo.html).

[woensug-choi]

strange. gdal_translate gebco4.tif test.asc -of GTiff -a_srs EPSG:3857 worked fine.

[woensug-choi]

@smtbhd32 try

# Resolution
DLON = 0.008
DLAT = 0.008
OVERLON = 0.001
OVERLAT = 0.001

for gebco4.tif, it's 478x498 (total of 238044) tiles and each tile only has 9 data points. The original DLON,DLAT resolution for input data is too small that the converted file didn't have any data in it.

[smtbhd32]

Hi @woensug-choi,
Thanks for your earlier suggestion!

Just wanted to update:
Running gdal_translate gebco4.tif test.asc -of GTiff -a_srs EPSG:3857 works fine for me too, same as you mentioned.

However, when I run the actual converter, I still encounter the same error.

# Resolution
DLON = 0.008
DLAT = 0.008
OVERLON = 0.001
OVERLAT = 0.001

Even after updating the parameters as you suggested, the error persists.
I'll try increasing the DLON and DLAT values further and will let you know what happens.

In the meantime, could you please guide me on how to better tune these parameters — especially OVERLON and OVERLAT?
From the documentation, I understand:

• DLON: size of bathymetry output tiles (Longitude direction)
• DLAT: size of bathymetry output tiles (Latitude direction)
• OVERLON: size of the buffer zone between tiles (Longitude direction)
• OVERLAT: size of the buffer zone between tiles (Latitude direction)

But I'm not fully sure how to set the OVERLON/OVERLAT optimally depending on the input file resolution or DLON/DLAT values.

Any advice would be greatly appreciated!

Thanks again for your help 🙏

[smtbhd32]

@smtbhd32 It's been quite some time since I've had hand on this tool. Preliminary suspect would be that the TIF files you are trying with doesn't have information of srs (https://gdal.org/en/stable/programs/gdalsrsinfo.html).

Also, I tried running gdalsrsinfo -v gebco4.tif to validate the srs, the file have valid srs data.

[woensug-choi]

@smtbhd32 The base reason it causes error is that the gebco input file is too coarse compared to the test files I've built upon. The OVERLON and OVERLAT is overlapping tile region between tiles. For the coarse input file, I would suggest not to use them at all since there wouldn't be any data. But I am not sure how it would react if set to zeros.

[smtbhd32]

Hi @woensug-choi, based on your suggestion, I checked the resolution of my file and compared it with the tutorial files. I found that the resolution of my file is 15 arc-minutes, while the tutorial file has a 1 arc-minute resolution.

So, I decided to download higher resolution data from the source suggested in the README of this repository. The link to the source of the file is: Arena Cove, California Coastal Digital Elevation Model.

I used the following parameters in the Bathymetry Converter automation script:

###################################################################
PREFIX = 'ArenaCover'
SOURCE = 'bathymetry_source/arena_cove_13_mhw_2009.nc'

# Flag for single tile generation
ONE_TILE_AT_ORIGIN = True

# Mesh simplification level (0 ~ 3)
SIMPLIFICATION_LEVEL = 3

# Range
STARTLON = -124.4300463
STARTLAT = 38.3999537
ENDLON = -124.2299537
ENDLAT = 38.5004632

# Resolution
DLON = 0.0
DLAT = 0.15
OVERLON = 0.0005
OVERLAT = 0.0005
###################################################################

However, when I tried running the tool on this file, it failed with the same error.

I’ve also attached a screenshot of the file statistics using gdalinfo -stats for the new file (arena_cove_13_mhw_2009.nc).