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Merged
trexfeathers merged 7 commits into from
Nov 21, 2023
Merged

Save LAEA grid #343

trexfeathers merged 7 commits into from
Nov 21, 2023

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@abooton
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@abooton abooton commented Jul 17, 2023 •
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Description
Saving of cubes on the Lambert Azimuthal Equal Area (LAEA) projection is added.
The LAEA template is described here: https://codes.ecmwf.int/grib/format/grib2/templates/3/140/

It is very similar to the Lambert Conformal projection specification in template_30, and so the coding was based on that.
https://codes.ecmwf.int/grib/format/grib2/templates/3/30/

Associated Issue
#344

@abooton abooton force-pushed the add_LAEA_template_140_saving branch from 228dbce to 56a2885 Compare July 17, 2023 07:43
@abooton abooton mentioned this pull request Jul 17, 2023
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@abooton abooton changed the title Add saving for the Lambert Azimuthual Equal Area grid Save LAEA grid Jul 17, 2023
@trexfeathers trexfeathers self-assigned this Jul 19, 2023
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pp-mo commented Jul 27, 2023

I just realised that we have an outstanding previous request to do this (plus another thing) ... #295.
The discussion there seems to have stalled, but we should probably choose one over the other somehow.

trexfeathers
trexfeathers reviewed Aug 10, 2023
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Thanks @abooton! I've compared this to the templates (thanks for the links), the Lambert Conformal code, and to #295; the changes make sense.

I have a few questions/suggestions below.

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trexfeathers commented Sep 20, 2023

@lbdreyer @abooton any thoughts on progressing this?

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trexfeathers commented Nov 8, 2023

Happy to close this if no longer important

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abooton commented Nov 14, 2023 •
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Sorry - I get so much GitHub spam I had not realised it had review comments on it. This is still important. It may still be need operationally.

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trexfeathers commented Nov 15, 2023 •
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Posting this outside any review comments to give me a common place to reference.

I tracked down template.3.140.def in eccodes, which I combined with ECMWF | Section 3 - Template 140 : Lambert azimuthal equal area projection to generate this:

Octets Key Type Content
15 shapeOfTheEarth codetable Shape of the Earth (see Code table 3.2)
16 scaleFactorOfRadiusOfSphericalEarth unsigned Scale factor of radius of spherical Earth
17-20 scaledValueOfRadiusOfSphericalEarth unsigned Scaled value of radius of spherical Earth
21 scaleFactorOfMajorAxisOfOblateSpheroidEarth unsigned Scale factor of major axis of oblate spheroid Earth
22-25 scaledValueOfMajorAxisOfOblateSpheroidEarth unsigned Scaled value of major axis of oblate spheroid Earth
26 scaleFactorOfMinorAxisOfOblateSpheroidEarth unsigned Scale factor of minor axis of oblate spheroid Earth
27-30 scaledValueOfMinorAxisOfOblateSpheroidEarth unsigned Scaled value of minor axis of oblate spheroid Earth
31-34 numberOfPointsAlongXAxis unsigned Nx - numberOfPointsAlongXAxis
35-38 numberOfPointsAlongYAxis unsigned Ny - numberOfPointsAlongYAxis
39-42 latitudeOfFirstGridPoint signed La1 - latitudeOfFirstGridPoint
43-46 longitudeOfFirstGridPoint signed Lo1 - longitudeOfFirstGridPoint
47-50 standardParallelInMicrodegrees signed Standard Parallel In Microdegrees
51-54 centralLongitudeInMicrodegrees signed Central Longitude In Microdegrees
55 resolutionAndComponentFlags codeflag Resolution and component flags (see Flag table 3.3)
56-59 xDirectionGridLengthInMillimetres unsigned Dx - X-direction grid length in millimetres
60-63 yDirectionGridLengthInMillimetres unsigned Dy - Y-direction grid length in millimetres
64 scanningMode codeflag Scanning mode (see Flag table 3.4)

trexfeathers
trexfeathers requested changes Nov 15, 2023
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@abooton
Altering names standardParallel to standardParallelInMicrodegrees and…
fd05ca8 
… centralLongitude to centralLongitudeInMicrodegrees
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abooton commented Nov 20, 2023

I have:

  • Renamed standardParallel to standardParallelInMicrodegrees (in _save_rules.py and in the unit tests)
  • Renamed centralLongitude to centralLongitudeInMicrodegrees (in _save_rules.py and in the unit tests)
  • Added the raising the exception if the false_easting and false_northing are not zero. (I can see this can be configured when creating the LAEA coord-system, but there isn't the slot in the GRIB to save it, hence the need to raise the exception).
  • I am happy that the lat and lon are set in degrees in the test _make_test_cube and are coded to be in micro-degrees in the test__template_specifics

@abooton abooton force-pushed the add_LAEA_template_140_saving branch 13 times, most recently from 9e1775f to 7b21ce6 Compare November 21, 2023 08:29
@abooton abooton force-pushed the add_LAEA_template_140_saving branch from 7b21ce6 to c0cae4f Compare November 21, 2023 08:42
@abooton abooton force-pushed the add_LAEA_template_140_saving branch from c0cae4f to 9ab66a5 Compare November 21, 2023 08:47
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trexfeathers commented Nov 21, 2023

The docs build failure is not a concern for this pull request - #365

@abooton abooton force-pushed the add_LAEA_template_140_saving branch 2 times, most recently from 4ef8d6e to b1f2aa3 Compare November 21, 2023 13:11
@abooton abooton force-pushed the add_LAEA_template_140_saving branch from b1f2aa3 to 9ca9e7f Compare November 21, 2023 13:23
@trexfeathers trexfeathers merged commit 58cb9ff into SciTools:main Nov 21, 2023
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trexfeathers commented Nov 21, 2023

Thanks very much for your contribution @abooton

@trexfeathers trexfeathers mentioned this pull request Jan 12, 2024
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@pp-mo pp-mo mentioned this pull request Apr 8, 2024
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@trexfeathers trexfeathers mentioned this pull request Aug 30, 2024
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