def get_drift_vectors(n1, x1, y1, n2, x2, y2, nsr=NSR(), **kwargs):
''' Find ice drift speed m/s
Parameters
----------
n1 : First Nansat object
x1 : 1D vector - X coordinates of keypoints on image 1
y1 : 1D vector - Y coordinates of keypoints on image 1
n2 : Second Nansat object
x1 : 1D vector - X coordinates of keypoints on image 2
y1 : 1D vector - Y coordinates of keypoints on image 2
nsr: Nansat.NSR(), projection that defines the grid
Returns
-------
u : 1D vector - eastward ice drift speed
v : 1D vector - northward ice drift speed
lon1 : 1D vector - longitudes of source points
lat1 : 1D vector - latitudes of source points
lon2 : 1D vector - longitudes of destination points
lat2 : 1D vector - latitudes of destination points
'''
# convert x,y to lon, lat
lon1, lat1 = n1.transform_points(x1, y1)
lon2, lat2 = n2.transform_points(x2, y2)
# create domain that converts lon/lat to units of the projection
d = Domain(nsr, '-te -10 -10 10 10 -tr 1 1')
# find displacement in needed units
x1, y1 = d.transform_points(lon1, lat1, 1)
x2, y2 = d.transform_points(lon2, lat2, 1)
return x2 - x1, y1 - y2, lon1, lat1, lon2, lat2
def get_displacement_km(n1, x1, y1, n2, x2, y2, ll2km='domain'):
''' Find displacement in kilometers using Domain'''
lon1, lat1 = n1.transform_points(x1, y1)
lon2, lat2 = n2.transform_points(x2, y2)
d = Domain(
'+proj=stere +lon_0=%f +lat_0=%f +no_defs' %
(lon1.mean(), lat1.mean()),
'-te -100000 -100000 100000 100000 -tr 1000 1000')
x1d, y1d = d.transform_points(lon1, lat1, 1)
x2d, y2d = d.transform_points(lon2, lat2, 1)
return x2d - x1d, y1d - y2d
def test_transform_points_inverse(self):
d = Domain(4326, "-te 25 70 35 72 -ts 500 500")
x, y = d.transform_points([25, 26, 27], [70, 71, 72], 1)
self.assertTrue(all(np.round(x) == [0, 50, 100]))
self.assertTrue(all(np.round(y) == [500, 250, 0]))
def test_transform_points(self):
d = Domain(4326, "-te 25 70 35 72 -ts 500 500")
lon, lat = d.transform_points([1, 2, 3], [1, 2, 3])
self.assertEqual(type(lon), np.ndarray)
self.assertEqual(type(lat), np.ndarray)
def test_transform_points_inverse(self):
d = Domain(4326, "-te 25 70 35 72 -ts 500 500")
x, y = d.transform_points([25, 26, 27], [70, 71, 72], 1)
self.assertTrue(all(np.round(x) == [0, 50, 100]))
self.assertTrue(all(np.round(y) == [500, 250, 0]))
def test_transform_points(self):
d = Domain(4326, "-te 25 70 35 72 -ts 500 500")
lon, lat = d.transform_points([1, 2, 3], [1, 2, 3])
self.assertEqual(type(lon), np.ndarray)
self.assertEqual(type(lat), np.ndarray)