turf.intersect raises "uncaught exception: [object Object]" on valid geometries

[vicvolk]

To-Do

Added by @DenisCarriere

• Returning a Feature<null>instead of returning undefined.
• Adding @turf/truncate to inputs.

To reproduce this error message (which I believe should not be raised), just run this code:

turf.intersect({"type": "Feature", "geometry":{"type":"Polygon","coordinates": [[[4869493.170354112,7598816.20365591],[4869512.279611183,7595796.941038646],[4873926.5179946525,7596007.14286643],[4873716.316166868,7598013.614858915],[4871671.62566024,7598758.875884696],[4869493.170354112,7598816.20365591]]]}},{"type": "Feature", "geometry":{"type":"Polygon","coordinates":[[[4894725.4051467,7624972.8484957],[4894725.4051469,7624972.8530041],[4894614.9242472,7624825.5926316],[4894398.2837739,7624987.6762962],[4894450.8149275,7625056.9040792],[4894668.7026646,7625096.7545718],[4894671.4728847,7625081.2756834],[4894674.9876194,7625066.9804281],[4894678.7586548,7625055.2998143],[4894682.9867902,7625043.5046946],[4894688.1291364,7625031.5950619],[4894694.8416008,7625017.8373286],[4894699.3280398,7625009.9516021],[4894705.0417681,7625000.4468024],[4894710.069852,7624992.8887655],[4894715.3264873,7624985.6742709],[4894721.1517534,7624977.9994939],[4894725.4051467,7624972.8484957]]]}})

The whole problem is with the second feature and I'm not sure what may be wrong with it.

[DenisCarriere]

Your coordinates should be in decimal degrees (WGS84 projection).

Please don't hesitate to reopen this issue if this is not resolved after the coordinate conversion is done.

[vicvolk]

Thanks! Did not know that. I will check it in a minute

[DenisCarriere]

👍 I'm assuming that jsts doesn't play well with other projections, especially if the crs is not defined. You can "easily" use QGIS or any other tool to convert your UTM or Mercator based data into WGS84.

[vicvolk]

I managed to reproduce this error with WGS84 coordinates. Here is a new test case:

turf.intersect({"type": "Feature", "geometry":{"type":"Polygon","coordinates": [[[43.741513133300735,56.20222135938059],[43.74237144018551,56.18856400988486],[43.77756202246089,56.187608768581725],[43.77927863623042,56.19639609165836],[43.763142466796836,56.20212587032091],[43.741513133300735,56.20222135938059]]]}},{"type": "Feature", "geometry":{"type":"Polygon","coordinates":[[[43.970066430113974,56.332893840607994],[43.970066430115764,56.33289386305967],[43.96907396330773,56.33216050512385],[43.96712784882449,56.3329676824026],[43.9675997442062,56.33331243182769],[43.96955706305079,56.33351088302814],[43.96958194836136,56.33343379993835],[43.969613521760365,56.3333626110674],[43.96964739754773,56.3333044427381],[43.96968537953426,56.3332457040905],[43.96973157401614,56.333186395086614],[43.969791873109784,56.333117882577056],[43.96983217547703,56.3330786121781],[43.969883502771644,56.3330312788475],[43.969928670817815,56.332993640236595],[43.96997589197615,56.33295771241299],[43.97002822123187,56.332919492368774],[43.970066430113974,56.332893840607994]]]}})

[vicvolk]

I have a long list of real world features and turf.intersect works perfect, until it hits this second feature. And it does not really matter what the first feature is, it may be absolutely arbitrary.

[vicvolk]

It seems like I have no rights to reopen this issue.

[DenisCarriere]

🤦‍♂️ Ops.. strange you can't reopen (my bad).

[DenisCarriere]

Oh I get it... looks like the intersection is "empty".

http://geojson.io/#id=gist:anonymous/1c584a17eac2f8f16c2cd4b6fa3fe664&map=11/56.2606/43.8558

I'm also getting a jsts related error:

Error
    at sn.l (/Users/mac/Github/turf/packages/turf-intersect/node_modules/jsts/dist/jsts.min.js:6:424)
    at new sn (/Users/mac/Github/turf/packages/turf-intersect/node_modules/jsts/dist/jsts.min.js:6:17532)
    at un.checkValid (/Users/mac/Github/turf/packages/turf-intersect/node_modules/jsts/dist/jsts.min.js:12:7761)
    at ln.checkValid (/Users/mac/Github/turf/packages/turf-intersect/node_modules/jsts/dist/jsts.min.js:12:8294)
    at Function.ln.checkValid (/Users/mac/Github/turf/packages/turf-intersect/node_modules/jsts/dist/jsts.min.js:12:8556)
    at ii.computeOverlay (/Users/mac/Github/turf/packages/turf-intersect/node_modules/jsts/dist/jsts.min.js:14:4)
    at ii.getResultGeometry (/Users/mac/Github/turf/packages/turf-intersect/node_modules/jsts/dist/jsts.min.js:13:31486)
    at Function.ii.overlayOp (/Users/mac/Github/turf/packages/turf-intersect/node_modules/jsts/dist/jsts.min.js:14:2252)
    at si.getResultGeometry (/Users/mac/Github/turf/packages/turf-intersect/node_modules/jsts/dist/jsts.min.js:14:5597)
    at Function.si.overlayOp (/Users/mac/Github/turf/packages/turf-intersect/node_modules/jsts/dist/jsts.min.js:14:5935)

[stebogit]

@vicvolk I read on the jsts docs that

• In some cases you might get a TopologyException thrown as an Error. This is expected if a calculation fails due to precision issues. To resolve this issue try reducing precision in the input and at the same time make sure the input is valid as defined by the OGC Simple Features specification. To reduce precision GeometryPrecisionReducer can be used.

Don't know exactly how to use GeometryPrecisionReducer, but using @turf/truncate on your polygons before applying @turf/intersect seems to solve the issue.
Please note that GeoJSON specs require coordinates with max 6 decimals anyway.

turf.intersect({"type":"Feature","properties":{},"geometry":{"type":"Polygon","coordinates":
[[[43.741513,56.202221],[43.742371,56.188564],[43.777562,56.187608],
[43.779278,56.196396],[43.763142,56.202125],[43.741513,56.202221]]]}},
{"type":"Feature","properties":{},"geometry":{"type":"Polygon","coordinates":
[[[43.970066,56.332893],[43.970066,56.332893],[43.969073,56.332160],
[43.967127,56.332967],[43.967599,56.333312],[43.969557,56.333510],
[43.969581,56.333433],[43.969613,56.333362],[43.969647,56.333304],
[43.969685,56.333245],[43.969731,56.333186],[43.969791,56.333117],
[43.969832,56.333078],[43.969883,56.333031],[43.969928,56.332993],
[43.969975,56.332957],[43.970028,56.332919],[43.970066,56.332893]]]}});
// undefined

@DenisCarriere should we truncate the inputs of @turf/intersect?
I noticed also that intersect returns undefined if there is no intersection between polygons; this means the test is in practice skipped, so we don't have an actual check on the output.
Should we modify the module's output returning null instead? I find it more appropriate because it's an actual value representing "nothing", and also it's a valid JSON so we could have null in the geojson output file and perform the test also on empty intersections.

[DenisCarriere]

With our recent @turf/helpers null geometry fix, we can definitely use Feature<null> for this module.

• 👍 Returning a Feature<null>instead of returning undefined.
• 👍 Adding @turf/truncate to inputs.

🤔 Don't know if we should apply @turf/truncate by default, might be best to give that option to the user if he wants to apply truncate or not.

[stebogit]

What I meant was applying it to the inputs (with no mutation), in order to avoid this issue with jsts. After all, any additional decimal after the 6th is irrelevant here, no?
I already have the fix btw, I'll commit later this evening or tomorrow

[DenisCarriere]

Is this error happening all the time?

Yes I know that we would be adding it to the inputs, but wouldn't that slow things down if it's not needed.

jsts is a mess, so I'm 👍 if we included the truncate fix directly in the module, that way we prevent those 5% errors that would normally occur from coordinate precision.