Swap coordinate pairs in a Polygon

[MaartenTromp]

Hi,

I have an "Poll an External Website for JSON" Input connector. The Polygon information in the json is wrapped in a string and looks like this:

"\"type\":\"polygon\",\"centerLat\":\"53.2841903320603\",\"centerLng\":\"6.1497098207473755\",\"polygonVertices\":[{\"lat\":53.284613668968,\"lon\":6.1477410793304},{\"lat\":53.28426089025,\"lon\":6.1476981639862},{\"lat\":53.283766995153,\"lon\":6.1516785621643},{\"lat\":53.284318617876,\"lon\":6.1517214775085}]}"

With some string processing I am able to make a valid Geometry and send it to an Hosted FeatureService. The polygon looks like this:

"{""rings"":[[[53.284613668968,6.1477410793304],[53.28426089025,6.1476981639862],[53.283766995153,6.1516785621643],[53.284318617876,6.1517214775085]]],""spatialReference"":{""wkid"":4326}}}"

The location is east of Somalia instead of the Netherlands because latitude and longitude are in the wrong order.

Is there a way to swap the coordinate pairs in the polygon?

Kind Regards, Maarten Tromp

[XanderBakker]

Hi Maarten Tromp‌,

Are you able to use RegEx in the string processing? Otherwise you may want to use the sdk and extend it:

Extending the GeoEvent Extension—Real-Time Data Feeds and Sensors | ArcGIS for Server

Kind regards, Xander

[MaartenTromp]

Hi Xander Bakker, good to hear from you!

My RegEx knowledge is limited, one of those handy things that doesn't stick very well:-(

There is a RegEx Processor in GeoEvent:

Processors—Real-time Data Feeds and Sensors | ArcGIS for Server

Any idea How to swap the two numbers in the PolygonString with RegEx?

Regards, Maarten

[XanderBakker]

Hi Maarten Tromp‌, nice to hear from you too and good to see you're doing some interesting stuff!

RegEx isn't my string either, but I do note you have some additional quotes in your output string.

{
"rings" : [
  [ [-97.06326,32.759], [-97.06298,32.755], [-97.06153,32.749], [-97.06326,32.759] ]
],
"spatialReference" : {"wkid" : 4326}
}

... and it woud be better to close the polygon (append the first item if the list of coordinates to the end of the list)

I would expect it to be possible to extract all ocurrences of lat and lon and form the correct list of coordinates using regex.

Maybe this can help: RegExr: Learn, Build, & Test RegEx

So, what do I hear, you're not going to the DevSummit this year?

I will be strange...

Good luck, Xander

[MaartenTromp · Accepted solution]

Hi,

It looks like the extra quotes and missing closing vertices is not an issue because the polygons appear in the Hosted FeatureService correctly.

In Notepad++ the correct result is created by using this RegEx to Search:

([0-9]+\.[0-9]+?),([0-9]+(\.[0-9]+)?)

And then this to replace:

\2,\1

But how to get this to work in the Processor "Field Calculator (Regular Expression)"?

Found it out myself by using the "Field Calculator" Processor and use this as expression:

replaceAll(polygonString2,'([0-9]+\.[0-9]+?),([0-9]+(\.[0-9]+)?)','$2,$1')

Regards, Maarten Tromp

[XanderBakker]

If the Processor Field calculator can be compared with the field calculator available at desktop and Python is supported you could try this (sorry no regex):

def constructJSON(in_string):
    in_string = in_string.replace('\"','')
    lst = in_string.split('polygonVertices:')
    use = str(lst[1][:-1]).replace("lat","'lat'").replace("lon","'lon'")
    lst_use = eval(use)
    lst_crds = []
    for dct_crd in lst_use:
        lst_crds.append([dct_crd['lon'], dct_crd['lat']])


    lst_crds.append(lst_crds[0])
    dct = {"rings":[],"spatialReference":{"wkid":4326}}
    dct["rings"] = [lst_crds]
    # return "'{0}'".format(dct)
    return dct

Exucute with:

in_string = '"\"type\":\"polygon\",\"centerLat\":\"53.2841903320603\",\"centerLng\":\"6.1497098207473755\",\"polygonVertices\":[{\"lat\":53.284613668968,\"lon\":6.1477410793304},{\"lat\":53.28426089025,\"lon\":6.1476981639862},{\"lat\":53.283766995153,\"lon\":6.1516785621643},{\"lat\":53.284318617876,\"lon\":6.1517214775085}]}"'
print constructJSON(in_string)

returns:

{'rings': [[[6.1477410793304, 53.284613668968], [6.1476981639862, 53.28426089025], [6.1516785621643, 53.283766995153], [6.1517214775085, 53.284318617876], [6.1477410793304, 53.284613668968]]], 'spatialReference': {'wkid': 4326}}

Not sure if the dictionary serves you or that it has to be casted to string.