error in convert proj

[sergiorosalesg]

Hi

I modified the pyfcom_preprocessing example to work with my mesh, but in the conversion from UTM to Lat Lon I got the following error
invalid projection: +proj=utm +zone=-18 +ellps=WGS84 +datum=WGS84 +units=m +no_defs +type=crs: (Internal Proj Error: proj_create: Error 1027 (Invalid value for an argument): UTM: Invalid value for zone)
When reviewing I realized that I cannot indicate that the coordinates correspond to the southern hemisphere. I will try to modify the code to incorporate that option

[jimc101]

I wonder if this is the same issue I encountered in PyLag, where I maintain a module that is based off coordinate.py in PyFVCOM. See issue 70 for further details. I ended up fixing this by switching to using EPSG codes rather than UTM zones when doing coordinate transformations. The updated cooridnate.py file includes the solution I adopted. Note this is a fairly major changes which alters the calling API. Thus, lots of existing scripts would likely have to change to use it. If this is the same problem, you could alternatively try limiting the version of pyproj/proj you use with PyFVCOM.

[sergiorosalesg]

as my problem is to get positions in the southern hemisphere I made the following change in _covert

the original line:
projection = pyproj.Proj("+proj=utm +zone={} +ellps={} +datum={} +units=m +no_defs".format(zone, ellipsoid, datum))

I change for:

if zone<0:
z=abs(zone)
projection = pyproj.Proj("+proj=utm +zone={} +south +ellps={} +datum={} +units=m +no_defs".format(z, ellipsoid, datum))
else:
projection = pyproj.Proj("+proj=utm +zone={} +ellps={} +datum={} +units=m +no_defs".format(zone, ellipsoid, datum))