DTED from_reference_point broken for southern latitudes

[kjurka]

from sarpy.io.DEM.DTED import DTEDInterpolator, DTEDList
import numpy as np

pt = np.array([-1, -70])
dted = DTEDList('/')
DTEDInterpolator.from_reference_point(pt, dted)

Traceback (most recent call last):
  File "sbh.py", line 6, in <module>
    DTEDInterpolator.from_reference_point(pt, dted)
  File "/share/home/kjurka@emagsys.com/git/sarpy/sarpy/io/DEM/DTED.py", line 671, in from_reference_point
    return cls.from_coords_and_list(
  File "/share/home/kjurka@emagsys.com/git/sarpy/sarpy/io/DEM/DTED.py", line 622, in from_coords_and_list
    return cls(dted_list.get_file_list(lat_lon_box, dem_type=dem_type), geoid_file, lat_lon_box=lat_lon_box)
  File "/share/home/kjurka@emagsys.com/git/sarpy/sarpy/io/DEM/DTED.py", line 204, in get_file_list
    raise ValueError(
ValueError: We have minimum longitude greater than maximum longitude [-1.1, -0.9, -64.27013115014498, -75.72986884985502]

sarpy/sarpy/io/DEM/DTED.py

Line 663 in bb17d79

lon_diff = min(15, lat_diff/(numpy.sin(numpy.deg2rad(ref_point[0]))))

The whole computation of lon_diff seems broken. Wouldn't you want cos here?

[petersontex]

Please test this with the new v1.3.62 release candidate.

The code is here: https://github.com/ngageoint/sarpy/releases/tag/v1.3.62rc1

Also available from PyPi (As a full release) here: https://pypi.org/project/sarpy/