How do I swap (reverse) the scanning order? for example changing north-to-south changed to south-to-north
Step-by-step guide
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- Ensure that the grid geometry of your GRIB message specifies both the latitudes:
latitudeOfFirstGridPointInDegrees and latitudeOfLastGridPointInDegrees
Check what scanning modes you have in your input file:
Code Block % grib_ls -p jScansPositively,iScansPositively input.gribUse the grib_set command to swap the scanning order for the latitudes:
Code Block % grib_set -s swapScanningY=1 input.grib output.grib
This changes the order in which the data is stored in the GRIB message
There is also the key "swapScanningX" to do the same task for longitudes (east-to-west changed to west-to-east).Note: This only works
Here is a way of visualising the different scanning orders:
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| The swapScanningX/Y keys only work for regular lat/lon grids and regular Gaussian grids. It is not to be used for reduced grids, Lambert, Polar stereographic, Mercator etc |
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| Check the resultant output GRIB file to ensure the data is shown correctly e.g., by plotting it |
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