topic Re: Create and display geometry object from WKB in Python Questions

Create and display geometry object from WKB

RobertKnapik — Fri, 02 Aug 2019 06:41:02 GMT

Is it possible to convert WKB geometry to geometry object and display it in ArcGIS Pro/ArcGIS Online etc.or save in geodatabase? I found in documentation something like this below, but how to use it?

FromWKB

I have a WKB string:

'010300002084080000010000000E0000007B14AEC74699244152B81E851B741D410AD7A3F0429924410000000002741D41713D0A571A992441333333331E741D419A9999990F99244100000000E0731D4100000080CF98244152B81E850B741D419A999919CB9824411F85EB51ED731D413D0AD723CA982441713D0AD7ED731D415C8FC2F5C49824411F85EB51CE731D410AD7A3F0B798244152B81E85D7731D4166666666AD982441C3F5285C97731D41E17A142E8598244166666666B2731D419A999999A3982441EC51B81E84741D415C8FC2F5F1982441B81E85EB51741D417B14AEC74699244152B81E851B741D41'

Thanks

Re: Create and display geometry object from WKB

NeilAyres — Fri, 02 Aug 2019 08:24:42 GMT

I have a WKB string:

Indeed this looks like a text string, not a byte array type as stated in the help.

How are you getting the WKB object?

Re: Create and display geometry object from WKB

RobertKnapik — Fri, 02 Aug 2019 12:41:02 GMT

from online service. Example is here: http://uldk.gugik.gov.pl/?request=GetParcelById&id=141201_1.0001.1867/2

Re: Create and display geometry object from WKB

BruceHarold — Fri, 02 Aug 2019 15:00:13 GMT

The data is not well formed, it contains hex-encoded WKB but is prepended with a 0 and newline character.

I attach the source for a Data Interoperability ETL tool that reads the geometry after discarding the leading junk.

You can use this with FME too.

Re: Create and display geometry object from WKB

JoshuaBixby — Sun, 12 Dec 2021 05:03:47 GMT

I think the bigger issue than the extra "0" line at the start and trailing newline character is the fact that the site if outputting EWKB and EWKT and not WKB and WKT. I find working with EWKB frustrating at best, so in this case I would simply get the results as EWKT since it is easier to break it down into a valid WKT string.

The following works with Python3:

>>> from urllib.request import urlopen
>>> import arcpy
>>>
>>> url = r"http://uldk.gugik.gov.pl/?request=GetParcelById&id=141201_1.0001.1867/2&result=geom_wkt"
>>> req = urlopen(url)
>>> EWKT = req.read().decode().split("\n")[1]
>>> EWKT
'SRID=2180;POLYGON((674979.39 482566.88,674977.47 482560.5,674957.17 482567.55,674951.8 482552,674919.75 482562.88,674917.55 482555.33,674917.07 482555.46,674914.48 482547.58,674907.97 482549.88,674902.7 482533.84,674882.59 482540.6,674897.8 482593.03,674936.98 482580.48,674979.39 482566.88))'
>>> SRID, WKT = EWKT.split(";")
>>> poly = arcpy.FromWKT(WKT, arcpy.SpatialReference(int(SRID.split("=")[1])))
>>> poly.area
2379.763699999483
>>> ‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Re: Create and display geometry object from WKB

BruceHarold — Fri, 02 Aug 2019 21:45:44 GMT

Hi Joshua, I never heard of EWKB/T, who needs that surprise, but like you show, easily handled. I'll request it be supported as a geometry encoding in Data Interoperablity.

Re: Create and display geometry object from WKB

JoshuaBixby — Fri, 02 Aug 2019 22:28:29 GMT

The Extended WKB/T formats are defined by PostGIS, but there are other packages that support them. From Chapter 4. Using PostGIS: Data Management and Queries :

4.1.2. PostGIS EWKB, EWKT and Canonical Forms
OGC formats only support 2D geometries, and the associated SRID is *never* embedded in the input/output representations.
PostGIS extended formats are currently superset of OGC one (every valid WKB/WKT is a valid EWKB/EWKT) but this might vary in the future, specifically if OGC comes out with a new format conflicting with our extensions. Thus you SHOULD NOT rely on this feature!
PostGIS EWKB/EWKT add 3DM, 3DZ, 4D coordinates support and embedded SRID information.

Re: Create and display geometry object from WKB

RobertKnapik — Sat, 03 Aug 2019 13:54:02 GMT

Thanks!

Re: Create and display geometry object from WKB

JoshuaBixby — Sat, 03 Aug 2019 13:59:32 GMT

If my response answered your question, please mark it correct to close out the question. Thanks.