Distance between Points

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10-09-2014 01:40 PM
JoaoOliveira2
New Contributor

here the thing-

in the same layer, I have POINT_X, POINT_Y and POINT_X_1, POINT_Y_1, as decimal degrees.

I´m trying to find the linear distance in meters from the 2 points.

I´m trying to get it with pyhton, using the below code, but I get always the same syntax error

000989 : Python syntax error: <value>

 

Any help appreciated

Thanks

Joao

 

 

pre-logic code

 

ef Haversine(Lat0, Lat1, Lon0, Lon1):

[INDENT]dlat = Lat0 - Lat1

dlon = Lon0 - Lon1

a = (math.sin(math.radians(dlat)/2 )*math.sin(math.radians(dlat)/2 )) + math.cos(math.radians(Lat1) )*math.cos(math.radians( Lat0 ) )*(math.sin(math.radians(dlon)/2 )*math.sin(math.radians(dlon)/2 ))

c = 2*math.atan2( math.sqrt(a ),math.sqrt(1-a ))

H = c * 6371

return H

[/INDENT]

 

 

Code:

Haversine( !POINT_Y! , !POINT_Y_1! , !POINT_X! , !POINT_X_1! )

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Accepted Solutions
SusanJones
Occasional Contributor II

At the moment this process is comparing apples and oranges and it will give incorrect results.

This said, the process needed is to build in a reproject function to take the coordinates from Geographic Coordinates (decimal degrees) into Map units (meters).

#Todo Get distance between 2 point

Step 1: Build up representation of 1st point in memory as PointGeometry Object

Step 2; Reproject point in map units

Step 3: Build up representation of 2nd point in memory as PointGeometryObject

Step 4: Reproject this into Map Units

Step 5: Compare the 2 points using Pythagoras Formula.

Attached is a function to perform the Reproject using the arcpy module

#projectSR

def projectSR (pt, sr): #sr = spatial reference, pt is geometry in memory

    #constantts

    gcs = arcpy.SpatialReference(2193)  #2193 = factory code for NZ Transverse Mercator

    gt = 'NZGD_2000_To_WGS_1984_1' #geographic transformation, if application

    coords = []

    ptgeom = arcpy.PointGeometry(pt, nztm).projectAs(gcs, gt)

    coords.insert(0,(ptgeom.centroid.X))

    coords.insert(1,(ptgeom.centroid.Y))

    del ptgeom

    return coords

Call projectSR to get the coordinates in map units meters and then you'll be able to use the Pythagoras theorem.

Susan

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2 Replies
SusanJones
Occasional Contributor II

At the moment this process is comparing apples and oranges and it will give incorrect results.

This said, the process needed is to build in a reproject function to take the coordinates from Geographic Coordinates (decimal degrees) into Map units (meters).

#Todo Get distance between 2 point

Step 1: Build up representation of 1st point in memory as PointGeometry Object

Step 2; Reproject point in map units

Step 3: Build up representation of 2nd point in memory as PointGeometryObject

Step 4: Reproject this into Map Units

Step 5: Compare the 2 points using Pythagoras Formula.

Attached is a function to perform the Reproject using the arcpy module

#projectSR

def projectSR (pt, sr): #sr = spatial reference, pt is geometry in memory

    #constantts

    gcs = arcpy.SpatialReference(2193)  #2193 = factory code for NZ Transverse Mercator

    gt = 'NZGD_2000_To_WGS_1984_1' #geographic transformation, if application

    coords = []

    ptgeom = arcpy.PointGeometry(pt, nztm).projectAs(gcs, gt)

    coords.insert(0,(ptgeom.centroid.X))

    coords.insert(1,(ptgeom.centroid.Y))

    del ptgeom

    return coords

Call projectSR to get the coordinates in map units meters and then you'll be able to use the Pythagoras theorem.

Susan

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DanPatterson_Retired
MVP Emeritus

If you still want to use Haversine, there are many examples on the web in python, for example

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