Query a Feature Layer to find polygons from a single point

brianbullas — Wed, 13 Apr 2016 22:42:29 GMT

I am using the .net SDK. The queries are actually being performed by a service bus, so there is no "user" viewing a map, only code to query a FeatureLayer.

What I am trying to do is take a geometry point from a particular FeatureLayer ( a single point), then Query another FeatureLayer that uses Polygons, and find all the polygons that overlap that particular geometry point.

I have found plenty of places to do the opposite (see if a point is within a ploygon), but what i need is to find all polygons that touch a point.

The code I am using:

var treeFeatureUrl = "<myurl for a feature layer with single points>";

var uri = new Uri(treeFeatureUrl);

var queryTask = new QueryTask(uri);

var queryParams = new Query("OBJECTID,AssetId")

{

OutFields = OutFields.All,

ReturnGeometry = true,

Where = $"AssetID=140156"

};

var queryResult = await queryTask.ExecuteAsync(queryParams);

var firstTree = queryResult.FeatureSet.Features.FirstOrDefault();

textBox1.Text += JsonConvert.SerializeObject(firstTree, Formatting.Indented) + Environment.NewLine;

textBox1.Text += Environment.NewLine + Environment.NewLine;

var url = "<myurl for a feature layer with polygon areas>";

var mapUri = new Uri(url);

var qTask = new QueryTask(mapUri);

var qparams = new Query("OBJECTID")

{

Geometry = firstTree.Geometry,

OutFields = OutFields.All,

ReturnGeometry = false,

SpatialRelationship = SpatialRelationship.Within,

};

var findREsult = await qTask.ExecuteAsync(qparams);

var foundFeatures = findREsult.FeatureSet.Features;

textBox1.Text += JsonConvert.SerializeObject(foundFeatures, Formatting.Indented) + Environment.NewLine;

textBox1.Text += Environment.NewLine + Environment.NewLine;

The above code never returns any results, probably because it's using the geometry from the firstTree as the search area.

I am not sure how to accomplish what it is I am trying to achieve: find all polygons that touch a certain single point.

Re: Query a Feature Layer to find polygons from a single point

AnttiKajanus1 — Thu, 14 Apr 2016 10:51:35 GMT

I would have a look if changing the spatial relationship on the second query changes the outcome. I think you should be able to use Intersects in this case.

topic Query a Feature Layer to find polygons from a single point in .NET Maps SDK Questions

Query a Feature Layer to find polygons from a single point

Re: Query a Feature Layer to find polygons from a single point