Python Sum Lat/lon Points Within Geographic Radius And Sum To Grid

Basically, my experimental program is trying to find the number of points that fall within a (e.g., 50km) radius of a valid point at a given time. My data is structured (but I can

Solution 1:

You would do something like the following... First, group your (x, y) coordinates for each group in a single points_x array:

points_1 = np.column_stack((LAT_1, LON_1))
...
points_n = np.column_stack((LAT_n, LON_n))

It may be a good idea to store them in a list of arrays:

points = [point_1, points_2, ..., points_n]

Now, make a kdTree out of each set of points:

import scipy.spatial as spsp
kdtrees = [spsp.cKdTree(p) for p in point]

And you are ready to go. If you now run the following code:

r = whatever_your_threshold_value_is
points_within_r = np.zeros((len(kdtrees), len(kdtrees)), dtype=np.int)
for j in xrange(len(kdtrees)):
    for k in xrange(j+1, len(kdtrees)):
        points_within_r[j, k] = kdtrees[j].count_neighbors(kdtrees[k], r, 2)
points_within_r = points_within_r + points_within_r.T

You should now find that points_within_r[j, k] holds how many points in points_j are within radius r of a point in points_k.

Keep in mind that distances here are the euclidean distance of the coordinates, disregarding the fact that what they measure are spherical angles.