Distance of shape points from given lat-long

Question

I have a point shapefile, and in its attribute table I have some coordinates (DISP_LON, DISP_LAT) which are slightly different from the actual location of the points.

I want to calculate the distance between actual point location and attribute table given co-ordinates, and want to insert in attribute table; preferably in Python, because I don't have ArcObjects SDK.

Initially I was trying to create line from the attribute coordinate and the Shapefile point coordinate. and then calculate line length.

To do some rough work I calculated the point lat-log in two new field name RP_LAT and RP_LONG and tried below code to create line by calculating distance between these two sets of coordinates:

import arcpy


in_rows = arcpy.SearchCursor("C:\Temp\PA.shp")
point = arcpy.Point()
array = arcpy.Array()
featureList = []
cursor = arcpy.InsertCursor("C:\Temp\Line.shp",["SHAPE@"])
feat = cursor.newRow()
for in_row in in_rows:
  # Set X and Y for start and end points
  point.X = in_row.RP_LON
  point.Y = in_row.RP_LAT
  array.add(point)
  point.X = float(in_row.DSPL)
  point.Y = float(in_row.DSPLT)
  array.add(point)   
  # Create a Polyline object based on the array of points
  polyline = arcpy.Polyline(array)
  # Clear the array for future use
  array.removeAll()
  # Append to the list of Polyline objects
  featureList.append(polyline)
  # Insert the feature
  feat.shape = polyline
  cursor.insertRow(feat)
del feat
del cursor

But the result is unexpected, it created strange long lines and empty records in a line shapefile.

My ultimate goal is find to distance of point coordinates and attribute given coordinates.

Answer 1

After Some Brain Storming i happened to figure out how it can be done wihtout creating lines between two points. With Havernsine Formula i prepared below script:

import arcpy
import math

# defining input
inputFCClass = arcpy.GetParameterAsText(0)
DispLong = arcpy.GetParameterAsText(1)
DispLAT = arcpy.GetParameterAsText(2)
OutputField = "Dist_DP_RP"
to_add = "[" + OutputField + "]"


#Create a list of existing field names and adding new field
fieldList = arcpy.ListFields(inputFCClass)  
fieldName = [f.name for f in fieldList]
for field in to_add:
    if not field in fieldName:
        arcpy.AddField_management(inputFCClass,OutputField,"DOUBLE")


#setting up progressor
RowCount  = arcpy.GetCount_management(inputFCClass)
PACnt = int(RowCount.getOutput(0))
arcpy.SetProgressor("step", "Counting Features...",0, PACnt, 1)


# hvernsine formula to calculate gedasic distance between two coordinate
def haversine(lon1, lat1, lon2, lat2):
    # convert decimal degrees to radians 
    lon1, lat1, lon2, lat2 = map(math.radians, [lon1, lat1, lon2, lat2])
    # haversine formula 
    dlon = lon2 - lon1 
    dlat = lat2 - lat1 
    a = math.sin(dlat/2)**2 + math.cos(lat1) * math.cos(lat2) *     math.sin(dlon/2)**2
    c = 2 * math.asin(math.sqrt(a)) 
    m = 6367000 * c
    return m
rows = arcpy.da.UpdateCursor(inputFCClass,(DispLong ,DispLAT,OutputField, "SHAPE@XY"))
for row in rows:
# If Condition to skip blank records
    if  (row[1]<> ' ') or (row[0]<> ' '):

       lon1 = float(row[0])
       lat1 = float(row[1])
       lon2 = row[3][0]
       lat2 = row[3][1]
       row[2] = haversine(lon1, lat1, lon2, lat2)
       rows.updateRow(row)
   arcpy.SetProgressorPosition()
del row, rows 

arcpy.SelectLayerByAttribute_management(inputFCClass,"CLEAR_SELECTION")
arcpy.SelectLayerByAttribute_management(inputFCClass,"CLEAR_SELECTION")
arcpy.ResetProgressor()