topic Calculating Percentage of feature layer's geometry in ArcGIS JavaScript Maps SDK Questions

Calculating Percentage of feature layer's geometry

Charan — Tue, 21 Nov 2023 21:35:55 GMT

Hi everyone, so I'm allowing users to draw buffer rings and I was wondering if its possible to calculate how much percentage of the feature layer's area/geometry is within the buffer. Is there an api to do such thing?

Re: Calculating Percentage of feature layer's geometry

BlakeTerhune — Tue, 21 Nov 2023 21:46:20 GMT

If you're working with the Maps SDK for JS, try using the intersect method of the geometryEngine. You would intersect the two geometries, calculate the area of the intersect result, then compare that with the total area of the original feature.

Re: Calculating Percentage of feature layer's geometry

irmcintosh — Tue, 21 Nov 2023 23:21:38 GMT

You could probably use arcade Expressions to capture that information,
unless you want to store it as an attribute.

Re: Calculating Percentage of feature layer's geometry

Charan — Wed, 22 Nov 2023 14:09:54 GMT

Hi @BlakeTerhune Will I be using the intersect results to calculate the area?

Re: Calculating Percentage of feature layer's geometry

BlakeTerhune — Wed, 22 Nov 2023 14:22:42 GMT

Yes.

percentage = (part/whole)*100

The "part" will be the intersect geometry area and the "whole" is the original feature geometry area.

Re: Calculating Percentage of feature layer's geometry

BlakeTerhune — Wed, 22 Nov 2023 14:18:20 GMT

Indeed, there are geometry functions for Arcade too.

Intersection
Area

Re: Calculating Percentage of feature layer's geometry

Charan — Wed, 22 Nov 2023 16:31:15 GMT

Hi @BlakeTerhune so I used the following code to get the geometries of the intersected results. However, I cant find the geometry for it

for (i=0; i< geoslabel.length; i++) {

let querycentroids2 = TradeArea_Data.createQuery()

querycentroids2.geometry = geoslabel[i].geometry;

querycentroids2.where = "year = 2022";

querycentroids2.spatialRelationship = "intersects";

querycentroids2.outFields=["DACODE"]

querycentroids2.returnGeometry = true

await TradeArea_Data.queryFeatures(querycentroids2). then (function (response) {

const values = response.features

if (values.length > 0) {

for (var a = 0; a < values.length; a++) {

console.log(values[a].attributes['DACODE'],geometryEngine.intersect(values[a].geometry, geoslabel[i].geometry))

}

)

}

Re: Calculating Percentage of feature layer's geometry

BlakeTerhune — Wed, 22 Nov 2023 16:01:09 GMT

Sorry, I don't understand the question. Please clarify your end goal.

Re: Calculating Percentage of feature layer's geometry

Charan — Wed, 22 Nov 2023 16:31:39 GMT

Hi @BlakeTerhune I have updated my question!

Re: Calculating Percentage of feature layer's geometry

BlakeTerhune — Wed, 22 Nov 2023 16:32:32 GMT

You are only working with the whole geometry of each feature in your loop. Nowhere are you calling the intersect method. I'm just guessing that geoslabel[i].geometry is the other geometry you want to calculate the percentage with...

for (i=0; i< geoslabel.length; i++) { let querycentroids2 = TradeArea_Data.createQuery(); querycentroids2.geometry = geoslabel[i].geometry; querycentroids2.where = "year = 2022"; querycentroids2.spatialRelationship = "intersects"; querycentroids2.outFields=["DACODE"]; querycentroids2.returnGeometry = true; await TradeArea_Data.queryFeatures(querycentroids2) .then (function (response) { const values = response.features for (var a = 0; a < values.length; a++) { const intersect_geom = geometryEngine.intersect(values[a].geometry, geoslabel[i].geometry); const intersect_area = geometryEngine.geodesicArea(intersect_geom, 'square-kilometers'); const feature_area = geometryEngine.geodesicArea(values[a].geometry, 'square-kilometers'); const intersect_percent = (intersect_area / feature_area) * 100; console.log(values[a].attributes['DACODE'], `feature_area = ${feature_area}`, `intersect_area = ${intersect_area}`, `intersect_percent = ${intersect_percent}`); } }); }