How do I sort polygons by their latitude?

Question

We have a set of polygons which we would like to sort and number according to their latitude. This will make it easier for local authorities to relate to the numbers of the objects.

I have looked around and not found any "out-of-the-box" solutions.

Any suggestions for how to solve this using ESRI tools or open source tools are interesting.

Answer 1

For an automated ArcGIS solution, try the following in model builder:

1. Add a new field "Latitude".
2. Calculate the "Latitude" field using Calculate Field: !SHAPE.FirstPoint.Y! (see attached field calculator screenshot). This calculation is based on the centroid of each polygon.
3. Create a new shapefile using Sort. Note that the new shapefile will have a new OBJECTID based on the sorted Latitude values.

Or, to loop through a workspace and perform the tasks on multiple shapefiles, here is an automated python approach:

# Import arcpy module
import arcpy
from arcpy import env

env.overwriteOutput = 1

env.workspace = r"C:\temp"
Dir = env.workspace

# List shapefiles
fclist = arcpy.ListFeatureClasses()

for fc in fclist:

    # Process: Add Field
    arcpy.AddField_management(fc, "Latitude", "DOUBLE", "", "", "", "", "NULLABLE", "NON_REQUIRED", "")

    # Process: Calculate Field
    arcpy.CalculateField_management(fc, "Latitude", "!SHAPE.FirstPoint.Y!", "PYTHON_9.3", "")

    # Process: Sort
    arcpy.Sort_management(fc, Dir + "\\" + fc + "_sort.shp", "Latitude ASCENDING", "UR")

Answer 2

1. Assuming your data has a projected coordinate system: Set data frame to a geographic coordinate system (WGS84). Add your data. (Set datum transformation if nessesary.)
2. Add a new field (ycoordinate). Right click field ycoordinate and calculate y-coordinate of centroid (use coordinate system of data frame for calculation.)
3. Export data to Excel
4. In Excel: sort field y-coordinate. In a new field (orderxls) calculate sequential numbers
5. Join excel table to your data in ArcMap.
6. Add a new field (order) in ArcMap. Use field calculator to copy values from orderxls to order.

Answer 3

One way to do this is to measure each polygons individual distance to a known point in the north. The North pole could be relevant here. This could be done making a script which iterates through all the polygons, makes a calculation of the distance to the North-Pole, and writes it to the file in a designated field.

A script solving this problem should be straight forward using arcpy.