Custom Geogrid Binary Data valid but output is 100% Zeros (SRTM)

[Alfred-Jose]

I am attempting to ingest a custom high-resolution SRTM dataset into WPS (Geogrid). I have successfully converted the GeoTIFFs to the WPS binary format and updated GEOGRID.TBL and index, but the resulting geo_em.d0X.nc topography field (HGT_M) is entirely zeros.

Diagnostics performed:

1. Binary Validity: Verified. I reverse-engineered one of the generated binary tiles back to GeoTIFF; the data is valid (signed int16, elevation ~2600m). od -t d2 confirms non-zero integer values in the files.
2. Naming Convention: Files are tiled and named xxxxx-XXXXX.yyyyy-YYYYY (e.g., 32001-34000.27450-29449).
3. Metadata: index file specifies projection = regular_ll, row_order = bottom_top, and known_lat/known_lon correspond to the bottom-left corner of the full dataset.
4. TBL/Namelist: GEOGRID.TBL rel_path is confirmed correct. geogrid.log shows "Processing data source..." followed by "Computed", indicating the files are found but interpolation yields zeros.

Configuration:

• Source: SRTM (Lat/Lon), dx/dy ~ 0.000808 deg.
• Domain: Mercator, centered at 33.3N, 77.1E (Ladakh region).
• Index Params: known_x=1, known_y=1, known_lat=14.99, wordsize=2, signed=yes.
  
  Since the binary data is valid and covers the domain area, why would Geogrid fail to map it? Is there a known issue with regular_ll indexing precision or known_lat definition (pixel center vs. corner) that could cause a total shift?

 

[kwerner]

Hello, and many apologies for the delay in response over the holidays. Because it's been a while, I want to first ask if you've made any progress with this, or is it still an issue?

 

[Alfred-Jose]

Still a problem, I tried playing with the HGT_M variable, and just swaped it with the values using SRTM dem Tiff file, but the thing is METGRID ran.
But failed during WRF run, due to CFL errors, as I was running using 9, 3, 1 km doms, and over the North Western Himalayas.

So kind of couldnt get the SRTM_3s into the model through the proper channel, or is this good approach??

 

[kwerner]

Theoretically, I believe either method should be okay to use. If you are able to successfully modify the HGT fields in the files, and they are present and as-expected in your met_em* files, then it shouldn't matter either way.

If you still want to try to get the SRTM data in your files before geogrid.exe, or if you ever do in the future, see these two previous posts that have some useful information about SRTM processing and plotting the static files to check for data accuracy.

how to add a new land use category and let WRF recognize it?
Shifted topography for SRTM1 data