How to add spatial reference information in distance calculation?

RajeshPatnaik

I have a long polyline with multiple vertices. i want shape length of only a portion of this polyline. For that I have extracted the coordinates of all vertices of this long polyline and created a list. I have removed the coordinates from this list which are not required, so that i have a list of coordinates only of the portion whose shape length is required.

Now i need to calculate the shape length using this coordinates list. For that i have used the following code:

import numpy as np
def dist_from_point_list(point_list):
    line = np.array(point_list, float)
    return np.sqrt(np.sum((line[1:] - line[:-1])**2, -1)).sum()
print(dist_from_point_list(point_list))

 

When I measure the distance in arcgis pro, the shape length is different from what i get using this function in my code. I have to somehow use the spatial reference/ projection information in my code to get the correct spatial length.

Any help in this regard would be highly appreciated. Thanks.

Anonymous User

You could create a temp feature and then measure it by using the shape@length and passing the spatial reference into the cursor.

feature_info = [[[1, 2], [2, 4], [3, 7]],
                [[6, 8], [5, 7], [7, 2], [9, 5]]]

# A list that will hold each of the Polyline objects
features = []

for feature in feature_info:
    # Create a Polyline object based on the array of points
    # Append to the list of Polyline objects
    features.append(
        arcpy.Polyline(
            arcpy.Array([arcpy.Point(*coords) for coords in feature])))

# Persist a copy of the Polyline objects using CopyFeatures
tmp = arcpy.CopyFeatures_management(features, "memory/lineSegment")
length = [f[0] for f in arcpy.da.SearchCursor(tmp, 'SHAPE@LENGTH', spatial_reference=arcpy.SpatialReference(4326))][0]

print(length)