about projection

[wzhengui]

Hi Basemap developer:

I am wondering whether you can help support the projection of "NAD83 / UTM zone", which is heavily used for the USA community.

Thanks Zhengui

[DWesl]

NAD83 is more an ellipsoid description than a projection, and from the below, basemap probably supports it: https://github.com/matplotlib/basemap/blob/461b40269088c936e2feaea12a33991bd96b63b5/packages/basemap/src/mpl_toolkits/basemap/init.py#L315-L318

UTM zone is a collection of specialized Transverse Mercator projections, as noted in the UTM example: https://github.com/matplotlib/basemap/blob/461b40269088c936e2feaea12a33991bd96b63b5/examples/utmtest.py#L15-L19 so this should be a matter of adding a lookup table to turn UTM zone into Transverse Mercator parameters (or perhaps UTM is designed such that this can be a helper function with multiplication rather than a lookup table).

Since it sounds like you have experience with UTM, perhaps you would be willing to expand that example to include a function to turn UTM zone into lon_0?

[wzhengui]

Thank you for the response. Yes, I think the modification might be more of adding a lookup table. However, I don't know how to do it. For the UTM example about converting UTM coordinates to lonlat, adding the following two lines should do the trick. Since this is a simple change, I didn't bother to submit a pull request. But if you you want me to do it, I can.

ly,lx=pyproj.Transformer.from_crs('epsg:26917','epsg:4326').transform(x,y) print('convert from utm to lon&lat from pyproj: ',lx,ly)

[DWesl]

If there's a simple correspondence between UTM zone and EPSG code/number, the projection coordinates (0, 0) might be on the lon_0, lat_0 basemap needs, do you know if that's the case?

[wzhengui]

1). I can confirm that there is EPSG number associated with UTM zone projection (see below).

2). No, I don't have an idea what basemap needs.

EPSG:26903 - NAD83 / UTM zone 3N EPSG:26904 - NAD83 / UTM zone 4N EPSG:26905 - NAD83 / UTM zone 5N EPSG:26906 - NAD83 / UTM zone 6N EPSG:26907 - NAD83 / UTM zone 7N EPSG:26908 - NAD83 / UTM zone 8N EPSG:26909 - NAD83 / UTM zone 9N EPSG:26910 - NAD83 / UTM zone 10N EPSG:26911 - NAD83 / UTM zone 11N EPSG:26912 - NAD83 / UTM zone 12N EPSG:26913 - NAD83 / UTM zone 13N EPSG:26914 - NAD83 / UTM zone 14N EPSG:26915 - NAD83 / UTM zone 15N EPSG:26916 - NAD83 / UTM zone 16N EPSG:26917 - NAD83 / UTM zone 17N EPSG:26918 - NAD83 / UTM zone 18N EPSG:26919 - NAD83 / UTM zone 19N EPSG:26920 - NAD83 / UTM zone 20N EPSG:26921 - NAD83 / UTM zone 21N EPSG:26922 - NAD83 / UTM zone 22N EPSG:26923 - NAD83 / UTM zone 23N EPSG:26929 - NAD83 / Alabama East EPSG:26930 - NAD83 / Alabama West EPSG:26932 - NAD83 / Alaska zone 2 EPSG:26933 - NAD83 / Alaska zone 3 EPSG:26934 - NAD83 / Alaska zone 4 EPSG:26935 - NAD83 / Alaska zone 5 EPSG:26936 - NAD83 / Alaska zone 6 EPSG:26937 - NAD83 / Alaska zone 7 EPSG:26938 - NAD83 / Alaska zone 8 EPSG:26939 - NAD83 / Alaska zone 9 EPSG:26940 - NAD83 / Alaska zone 10 EPSG:26941 - NAD83 / California zone 1 EPSG:26942 - NAD83 / California zone 2 EPSG:26943 - NAD83 / California zone 3 EPSG:26944 - NAD83 / California zone 4 EPSG:26945 - NAD83 / California zone 5 EPSG:26946 - NAD83 / California zone 6 EPSG:26948 - NAD83 / Arizona East EPSG:26949 - NAD83 / Arizona Central EPSG:26950 - NAD83 / Arizona West EPSG:26951 - NAD83 / Arkansas North EPSG:26952 - NAD83 / Arkansas South EPSG:26953 - NAD83 / Colorado North EPSG:26954 - NAD83 / Colorado Central EPSG:26955 - NAD83 / Colorado South EPSG:26956 - NAD83 / Connecticut EPSG:26957 - NAD83 / Delaware EPSG:26958 - NAD83 / Florida East EPSG:26959 - NAD83 / Florida West EPSG:26960 - NAD83 / Florida North EPSG:26961 - NAD83 / Hawaii zone 1 EPSG:26962 - NAD83 / Hawaii zone 2 EPSG:26963 - NAD83 / Hawaii zone 3 EPSG:26964 - NAD83 / Hawaii zone 4 EPSG:26965 - NAD83 / Hawaii zone 5 EPSG:26966 - NAD83 / Georgia East EPSG:26967 - NAD83 / Georgia West EPSG:26968 - NAD83 / Idaho East EPSG:26969 - NAD83 / Idaho Central EPSG:26970 - NAD83 / Idaho West EPSG:26971 - NAD83 / Illinois East EPSG:26972 - NAD83 / Illinois West EPSG:26973 - NAD83 / Indiana East EPSG:26974 - NAD83 / Indiana West EPSG:26975 - NAD83 / Iowa North EPSG:26976 - NAD83 / Iowa South EPSG:26977 - NAD83 / Kansas North EPSG:26978 - NAD83 / Kansas South EPSG:26979 - NAD83 / Kentucky North EPSG:26980 - NAD83 / Kentucky South EPSG:26981 - NAD83 / Louisiana North EPSG:26982 - NAD83 / Louisiana South EPSG:26983 - NAD83 / Maine East EPSG:26984 - NAD83 / Maine West EPSG:26985 - NAD83 / Maryland EPSG:26986 - NAD83 / Massachusetts Mainland EPSG:26987 - NAD83 / Massachusetts Island EPSG:26988 - NAD83 / Michigan North EPSG:26989 - NAD83 / Michigan Central EPSG:26990 - NAD83 / Michigan South EPSG:26991 - NAD83 / Minnesota North EPSG:26992 - NAD83 / Minnesota Central EPSG:26993 - NAD83 / Minnesota South EPSG:26994 - NAD83 / Mississippi East EPSG:26995 - NAD83 / Mississippi West EPSG:26996 - NAD83 / Missouri East EPSG:26997 - NAD83 / Missouri Central EPSG:26998 - NAD83 / Missouri West