topic Re: creating a polygon (footprint) with 4 coordinates from excel file in Data Management Questions

creating a polygon (footprint) with 4 coordinates from excel file

NikolaiKirch — Fri, 25 Nov 2016 15:45:10 GMT

So i got ArcMap Basic and i want to bring my 100000 rows thick excel table to GIS.

In overall 8 columns are my 4 coordinates: coordinate 1 lat, coordinate 1 long, coordinate 2 lat ....

would be easy to average the 4 coordinates and just show for every row one point.

But i need to present every row as a polygon. A polygon square with 4 vertex (one for every coordinate). Like a footprint.

Does anyone have an idea?

Re: creating a polygon (footprint) with 4 coordinates from excel file

DanPatterson_Retired — Fri, 25 Nov 2016 16:30:03 GMT

The obvious choice is Create Fishnet—Help | ArcGIS for Desktop if your polygon pattern is regular and just a bunch of sequential rectangles.

If not, they you might have to provide some more information and give some sense on your familiarity with python

Re: creating a polygon (footprint) with 4 coordinates from excel file

NikolaiKirch — Mon, 28 Nov 2016 07:44:29 GMT

Its not regular.

for example these are the coordinates from one row for one polygon:

coordinate 1 lat coordinate 1 long coordinate 2 lat

50,48508401

6,98761143

49,67204584

6,788479888

49,62808362

7,198308726

50,44104231

7,404422742

i need to create a heatmap with these polygons.

My python skills are quite rudimentary.

Re: creating a polygon (footprint) with 4 coordinates from excel file

NeilAyres — Mon, 28 Nov 2016 08:41:13 GMT

Well the best way is to write some python to ingest this and create a polygon featureclass from the file.

Its not too difficult.

I imagine that this is actually a text file, rather than xls or something.

Is that your decimal separator ","?

If you can post a portion of the file here, I am sure someone can take a look.

Re: creating a polygon (footprint) with 4 coordinates from excel file

FC_Basson — Sat, 11 Dec 2021 19:04:54 GMT

Here's a basic version of a script that might work for you:

import arcpy, os, csv, numpy as np
csvfile = r'D:\GIS\Scripts\points.csv'
arcpy.env.workspace = r'D:\GIS\ArcGIS\scratch.gdb'
polygons = arcpy.mapping.Layer(r'D:\GIS\ArcGIS\scratch.gdb\csv_points_poly')
csv = np.genfromtxt(csvfile, delimiter=",")
srWGS = arcpy.SpatialReference(4326)
# from second line of array
cur = arcpy.da.InsertCursor(polygons, ("ID", "SHAPE@"))
for coord in csv[1:]:
 print coord
 array = arcpy.Array()
 # point 1
 pnt1 = arcpy.PointGeometry(arcpy.Point(coord[2],coord[1]),srWGS,False, False)
 array.append(pnt1.centroid)
 # point 2
 pnt2 = arcpy.PointGeometry(arcpy.Point(coord[4],coord[3]),srWGS,False, False)
 array.append(pnt2.centroid)
 # point 3
 pnt3 = arcpy.PointGeometry(arcpy.Point(coord[6],coord[5]),srWGS,False, False)
 array.append(pnt3.centroid)
 # point 4
 pnt4 = arcpy.PointGeometry(arcpy.Point(coord[8],coord[7]),srWGS,False, False)
 array.append(pnt4.centroid)
 polygon = arcpy.Polygon(array,srWGS)
 cur.insertRow((coord[0],polygon))‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

First I created the output polygon feature class "csv_points_poly" in my scratch GDB with an additional "ID" field.

Then assuming your XLS/CSV file looks something like this:

ID,LAT1,LON1,LAT2,LON2,LAT3,LON3,LAT4,LON4
1,-34.5,17,-34.5,17.5,-35,17.5,-35,17
2,-34,18,-34,18.5,-34.5,18.5,-34.5,18
3,-33.5,19,-33.5,19.5,-34,19.5,-34,19
4,-32.5,20,-32.5,20.5,-33,20.5,-33,20
5,-31.5,21,-31.5,21.5,-32,21.5,-32,21
6,-30.5,22,-30.5,22.5,-31,22.5,-31,22
7,-30,23,-30,23.5,-30.5,23.5,-30.5,23
8,-29,24,-29,24.5,-29.5,24.5,-29.5,24
9,-28,25,-28,25.5,-28.5,25.5,-28.5,25
10,-27,26,-27,26.5,-27.5,26.5,-27.5,26‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

You can use numpy to make an array of your data, which you can iterate to build a polygon for each row.

Re: creating a polygon (footprint) with 4 coordinates from excel file

NikolaiKirch — Mon, 28 Nov 2016 10:16:15 GMT

i changed the paths for my directories, created the feature class with an additional ID field and saved my xls as csv just like your table. My (german) csv seems to be seperated trough ";", i changed

csv = np.genfromtxt(csvfile, delimiter=",") to ";"

otherwise the script wont work.

Unfortunately the whole result is like:

[ 7899.    nan    nan    nan    nan    nan    nan    nan    nan]
[ 7900.    nan    nan    nan    nan    nan    nan    nan    nan]
[ 7901.    nan    nan    nan    nan    nan    nan    nan    nan]

with some:

[ 26710.     nan     nan     nan     nan     nan     nan     nan     nan]
[ 2.67110000e+04   4.70000000e+01   7.00000000e+00   4.60000000e+01
   7.00000000e+00   4.60000000e+01   8.00000000e+00   4.70000000e+01
   8.00000000e+00]
[ 26712.     nan     nan     nan     nan     nan     nan     nan     nan]

is it possible that my my lat or lon coordinates are too big for "double"?

they look like that:

54,2506883777232

Re: creating a polygon (footprint) with 4 coordinates from excel file

FC_Basson — Mon, 28 Nov 2016 10:44:39 GMT

No I don't think your coordinate float value is "too big", but make sure that the float is not expressed as a comma value (54,2506883777232), but with dot notation (54.2506883777232). Revisit your input file's values to ensure that the field formatting is correct..

Re: creating a polygon (footprint) with 4 coordinates from excel file

NeilAyres — Mon, 28 Nov 2016 11:34:27 GMT

You will have to go into your windows regional settings and change the decimal separator from "," to "."

Re: creating a polygon (footprint) with 4 coordinates from excel file

NikolaiKirch — Mon, 28 Nov 2016 12:05:44 GMT

it works fine, but it seems to me that lat and long are reversed?

Re: creating a polygon (footprint) with 4 coordinates from excel file

FC_Basson — Mon, 28 Nov 2016 12:09:56 GMT

Oh yes, for creating a point geometry the notation is Lon/Lat (Writing geometries—ArcPy Get Started | ArcGIS for Desktop ) and not the format I used in my script. So just change the sequence of the coordinate pairs to match the LAT and LON fields (see edits to my original script code):

pnt1 = arcpy.PointGeometry(arcpy.Point(coord[2],coord[1]),srWGS,False, False)‍‍‍