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Multidimensional Raster Projections

JamesHead-Mears1

I've been working with Mutlidimensional NetCDF files from TUFLOW recently and have come across some issues with the projection of the data. I've come across a couple of different issues like where the data is mirrored (E,N swapped but origin correct) or the origin of the dataset is coming from a different point of the raster (eg bottom of the raster instead of middle).

Has anyone else come across something like this?

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Accepted answers

JamesHead-Mears1

Thanks everyone. I ended up getting additional support back from TUFLOW and they are adding another upvote to improve the compatibility of their NC outputs. In the meantime they provided me with a script that utilises the aforementioned netcdf4 python library which writes the projection files into the NC file. As far as I can tell ESRI seems to ignore the accompanying proj file.

I'll look at converting the supplied python script into a ESRI toolbox script and post it here for anyone else that runs into this issue.

All comments

JamesHead-Mears1

TilmannSteinmetz2

Hi James, when we started to work with NetCDFs in Image Services a couple of years ago, we did have a bit of trouble with coordinate system definitions: our science data are recorded on a rotated pole coordinate system and then written into NetCDF format - that 'rotated pole' coordinate reference system was the first thing which had to change.

After using a more commonly understood projection system, we figured out that the way the scientists had defined that system was common in software clients in the climate science world, but couldn't easily be read into a mosaic dataset. After changing the definition to a common text string it started to work very well.

An example of that definition (from https://epsg.io/3851 ) - you want to use the one called "Esri WKT"

PROJCS["NZGD_2000_NZ_Continental_Shelf_2000",
    GEOGCS["GCS_NZGD_2000",
        DATUM["D_NZGD_2000",
            SPHEROID["GRS_1980",6378137.0,298.257222101]],
        PRIMEM["Greenwich",0.0],
        UNIT["Degree",0.0174532925199433]],
    PROJECTION["Lambert_Conformal_Conic"],
    PARAMETER["False_Easting",3000000.0],
    PARAMETER["False_Northing",7000000.0],
    PARAMETER["Central_Meridian",173.0],
    PARAMETER["Standard_Parallel_1",-37.5],
    PARAMETER["Standard_Parallel_2",-44.5],
    PARAMETER["Latitude_Of_Origin",-41.0],
    UNIT["Meter",1.0]]

Cheers,

Tilmann

PS: after reading the above, I notice that I should clarify that we _generate_ the NetCDFs that we work with using scripts written here, so obviously we were able to modify the code used to do that - whereas I'm not sure whether you can do that with TUFLOW, which I don't know.

GuenterDoerffel

James,

I am far from being a NetCDF specialist, but the issues you face sound familiar. If you read this page of the ArcGIS Pro Doc:
https://pro.arcgis.com/en/pro-app/latest/tool-reference/multidimension/essential-netcdf-vocabulary.htm

you will find a hint regarding NetCDF conventions ... and that within ArcGIS we currently support the Climate and Forecast (CF) and the Cooperative Ocean/Atmosphere Research Data Service (COARDS) conventions. It also states "others might work" ... but to my experience this is exactly where the problems with coordinates and reading data/dimensions come from. The link above also has additional links regarding conventions in it.
If you want to dig in deeper, ArcGIS Pro today comes with the pre-installed python library netcdf4 which might be a way to get to the data you want ...

Regards
Guenter

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