How can I create grid of coordinates from a center point in python?-CodePudding

The

For example having an input of latitude and longitude center coordinate (red dot):

lat = 40.8264859 lon = -3.6805897

In a function that then returns you a list of lists or array with the corresponding lat,lon grid with 100 meters from each other, and a max number of coordinates away from the center point (in this image case that value would be 2). For example:

def get_grid_of_coordinates_from_center(lat, lon, meters_between_coor, coors_away_from_center): ... return list_of_lists

CodePudding user response：

might need to check some edge cases (I used numbers that are easy to work with), but this seems to work

import matplotlib.pyplot as plt import numpy as np mid_x, mid_y, max_x, max_y, min_x, min_y,step_size,num_points = 5, 5, 11, 11, 0, 0, 1, 10 x_range = np.concatenate((np.arange(min_x, mid_x, step_size), np.arange(mid_x, max_x, step_size))) y_range = np.concatenate((np.arange(min_y, mid_y, step_size), np.arange(mid_y, max_y, step_size))) data = np.array([[x, y] for x in x_range for y in y_range]) # cartesian prod plt.scatter(data[:, 0], data[:, 1]) plt.scatter(mid_x, mid_y, color='r') plt.show()

plot:

CodePudding user response：

Try this vectorized approach. The equation to offset a lat-long with meters is inspired from

EXPLANATION

I break the above steps down into separate functions (and use np.vectorize) for ease of understanding.

First you need a vectorized function that takes in (lat, long) and offsets it by meters in both X and Y directions.

You need to create an offset_grid

You can start by using np.linspace to create a range from start to end with the required number of points

Next, you can use this to create a grid with X, Y matrices, using np.meshgrid

With the vectorized function and the offset_grid you can apply the lat long offset on each of the values and then reshape to get your (x,y) values for each point in the (n,n) expected matrix.

Let's start with a function that offsets lat, long with some x and y meters.

#Offset any lat long by x, y meters def lat_long_offset(lat, lon, x, y): ''' lat, lon : Provide lat lon coordinates x, y : Provide offset of x and y on lat and long respectively This needs to be in meters! The approximation is taken from an aviation formula from this stack exchange https://gis.stackexchange.com/questions/2951/algorithm-for-offsetting-a-latitude-longitude-by-some-amount-of-meters ''' #Earth’s radius, sphere R=6378137 #Coordinate offsets in radians dLat = x/R dLon = y/(R*np.cos(np.pi*lat/180)) #OffsetPosition, decimal degrees latO = lat dLat * 180/np.pi lonO = lon dLon * 180/np.pi return latO, lonO #Create a vectorized offset function lat_long_offset_vec = np.vectorize(lat_long_offset)

Once we have this function ready, we can simply work on the offset grid that we need to apply offsets in all directions to get the relevant point coordinates in lat, long format.

#Create offset_grid and return coordinates def get_mesh(lat, lon, dist, coors): #calculate min and max range for coordinates over an axis mini, maxi = -dist*coors, dist*coors #calculate number of points over an axis n_coord = coors*2 1 #create an axis from min to max value with required number of coordinates axis = np.linspace(mini, maxi, n_coord) #create an "offset_grid" for X and Y values for both axis. X, Y = np.meshgrid(axis, axis) #calcualte offset coordinates for "offset_grid" in meters mesh = lat_long_offset_vec(lat, lon, X, Y) #Transpose to get the (x,y) values for the offset_grid's shape mesh_x_y_format = np.stack(mesh).transpose(1,2,0) return mesh_x_y_format output = get_mesh(50, -10, 100, 2) print('Shape of output grid:', output.shape) print('Note: 2 values (x,y) for each point in the expected (5,5) grid') print('') print('Output coordinates') print(output)

Shape of output grid: (5, 5, 2) Note: 2 values (x,y) for each point in the expected (5,5) grid Output coordinates [[[ 49.99820337 -10.00279506] [ 49.99910168 -10.00279506] [ 50. -10.00279506] [ 50.00089832 -10.00279506] [ 50.00179663 -10.00279506]] [[ 49.99820337 -10.00139753] [ 49.99910168 -10.00139753] [ 50. -10.00139753] [ 50.00089832 -10.00139753] [ 50.00179663 -10.00139753]] [[ 49.99820337 -10. ] [ 49.99910168 -10. ] [ 50. -10. ] #<- Notice the original coordinate at center [ 50.00089832 -10. ] [ 50.00179663 -10. ]] [[ 49.99820337 -9.99860247] [ 49.99910168 -9.99860247] [ 50. -9.99860247] [ 50.00089832 -9.99860247] [ 50.00179663 -9.99860247]] [[ 49.99820337 -9.99720494] [ 49.99910168 -9.99720494] [ 50. -9.99720494] [ 50.00089832 -9.99720494] [ 50.00179663 -9.99720494]]]

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