Open smalers opened 1 year ago
If I understand the issue you describe, there are two things to be aware of regarding the coordinates in the .txt files:
The Special Report National Operational Hydrologic Remote Sensing Center SNOw Data Assimilation System (SNODAS) Products at NSIDC was written in 2003 when we initially started archiving SNODAS data produced by NOHRSC, so it is a little outdated. The user guide is the most recent documentation Snow Data Assimilation System (SNODAS) Data Products at NSIDC, Version 1 (G02158) and we keep it updated with any changes/new information.
When users are trying to convert the binary files to geotiff or netcdf I actually point them to the help article: How do I convert SNODAS binary files to GeoTIFF or NetCDF? which has more up-to-date information. This includes the note about the spatial shift in the data for files prior to and after 01 October 2013. It is very small (~5% of a 1km grid cell) but I just wanted to mention it in case you hadn't come across it.
I hope this helps, but if I have misunderstood your question or if you have any further questions then please let me know.
NOAA provides this documentation describing the SNODAS data files:
The documentation is from 2003 and I don't see a more recent version. It is generally accurate. However, the appendix B information is not quite accurate. Current
.txt
files have information similar to the following. Note that the values forBenchmark x-axis coordinate
(ulxmap
in thehdr
file) andBenchmark y-axis coordinate
(ulymap
in thehdr
file) in the following are different from the above documentation.I have updated the SNODAS Tools Python code for version 2.1.0 to scrape the the values out of the
txt
file for thehdr
file needed for processing. I don't know when the values changed or how often they change but assuming that they do not change will cause a data shift (a few hundred meters horizontally?). I have reached out to SNDAS support. I may try to figure that out because some results may have shifted. I'll need to reprocess some data.