GEOSwift: Invalid Intersection result after upgrading to GeoSwift 7.0.0+

I’m using GeoSwift for performing geospatial operations in a mobile app. Prior to v7.0.0, the intersection operation used to work as expected, however, after upgrading to v7.0.0 from 6.2.0, the same method returned a different result. Please find the attached geoJson files in the zip file for reproducing the error.

Parent: polygon.json (polygon) LineString: multiLinestring.json (multiLineString)

And here is the code I am using for the same

  do {
             for lineString in multiLineString.lineStrings {
                if try lineString.intersects(polygon) {
                    let intersectingGeometry = try lineString.intersection(with: polygon)
                    // Handle Intersection here
                }
            } 
   } catch {
            DDLogError("Unable to get the intersection of line string with the geometry. \(error.localizedDescription)")
            return nil
        }

Essentially I am getting a different result when I run the intersection operation on GeoSwift v6.2.0 (Expected) and GeoSwift v7.1.0 (Possibly Incorrect)

Is there something else I need to do to find an intersection in the newer versions of GeoSwift? Thanks a lot for helping 😃

Here is the environment I am using Xcode : 12.2 GeoSwift: 7.1.0 GEOS: 5.1.0

Apologies for not being able to find a simpler example to illustrate the problem 😅

// Zip containing the geojson files TestData.zip

About this issue

Original URL
State: closed
Created 3 years ago
Comments: 30 (12 by maintainers)

Most upvoted comments

This has been fixed in GEOS. See GEOS 1093.

dr-jts on Jan 27, 2021

Thanks! I realize now that 8.0.1 was never published to CocoaPods because the only change was to the Swift Package Manager configuration. Glad it’s working!

macdrevx on Feb 19, 2021

That worked! However, I had to set it to 8.0.0, setting it to 8.0.1 resulted in the following error

[!] CocoaPods could not find compatible versions for pod "GEOSwift":
  In Podfile:
    GEOSwift (= 8.0.1)

None of your spec sources contain a spec satisfying the dependency: `GEOSwift (= 8.0.1)`.

You have either:
 * mistyped the name or version.
 * not added the source repo that hosts the Podspec to your Podfile.

Additionally, I was able to test the fix and I can confirm that the issue has indeed been resolved in the latest version of GEOS (3.9.1)

india2sarthak on Feb 19, 2021

No timeline for next GEOS release at the moment.

dr-jts on Jan 27, 2021

Sounds great! Thanks @dr-jts.

@india2sarthak I’m not sure when we should expect this to land in a GEOS release, but when it does, we can update our CocoaPods & SPM packages accordingly so you’ll have access to it and won’t need to maintain a fork. We can leave this issue open until then.

macdrevx on Jan 16, 2021

It looks like there is a fairly simple fix to this ordering problem. I will add that to JTS, and we’ll work through the pipeline to land in GEOS too.

dr-jts on Jan 16, 2021

This is now available in version 8.0

macdrevx on Jan 9, 2021

@india2sarthak I’ve pushed a branch with this change. Please test it out and let us know whether it meets your needs.

The branch is named normalize and it adds a method normalized() -> Geometry that can be used on any type conforming to GeometryConvertible.

macdrevx on Jan 7, 2021

@india2sarthak in the mean time, one option you have is to downgrade geos to 5.0.0. This will likely resolve this issue for you.

macdrevx on Jan 7, 2021

I think we’ll need to bubble this up to the GEOS folks to get their perspective. I’ll ask for guidance on their mailing list.

macdrevx on Jan 6, 2021

Thanks for reporting this. I’ll take a look in the next few days.

macdrevx on Jan 5, 2021