topic Re: Best way to select features within features in ArcGIS JavaScript Maps SDK Questions

Best way to select features within features

TimWitt2 — Fri, 17 Jul 2015 14:27:36 GMT

Hey everybody,

I am looking for a way to select points from a feature layer that fall within this feature layer: Layer: Atl_slr_merged_2ft (ID: 6)

It sounds easy enough if you use ArcGIS Desktop but in javascript I am running into issues.

Using the method described here would work, union and then use the geometry of the union feature to select what falls within it. But if your feature layer has thousands of polygons, the union would take forever.

So my question is, am I approaching this issue wrong? Is my only option to union the layer before publishing it on a server ( which I sadly can't do, because I don't have the feature layer and rely on NOAA hosting it).

Any input would be greatly appreciated!

Thanks,

Tim

Re: Best way to select features within features

RobertScheitlin__GISP — Fri, 17 Jul 2015 14:38:03 GMT

Tim,

You may need to consider your workflow for this. Do you really need to use all of the polygons from the NOAA map service in your app? Can you not set your workflow to minimize the intersect query before it is performed (i.e. have the user do some query to minimize the polygons evaluated or only query the polygons in the current map extent)?

Re: Best way to select features within features

RickeyFight — Fri, 17 Jul 2015 14:39:57 GMT

Tim,

Are you thinking something like this?

Webapp- Show points within a selected polygon

Re: Best way to select features within features

TimWitt2 — Fri, 17 Jul 2015 14:45:32 GMT

Robert,

that might be an idea. Maybe I should have explained what my goal is.

I would like the user to be able to add their point featurlayer and see which points would fall within the flood zone.

Tim

Re: Best way to select features within features

RobertScheitlin__GISP — Fri, 17 Jul 2015 14:54:20 GMT

Tim,

What does their point FL represent? Will it be a handful of points, hundreds, thousands?

Re: Best way to select features within features

TimWitt2 — Fri, 17 Jul 2015 14:56:39 GMT

Robert,

I would say anywhere between 10 - 200.

Re: Best way to select features within features

RobertScheitlin__GISP — Fri, 17 Jul 2015 15:11:23 GMT

Tim,

I would tackle this in a multi-step solution then.

Take the users input point layer and add all the points to a new MultiPoint Geometry
Use the new MultiPoint geom to query the NOAA Polygons.
Take those NOAA Polygon results from the query and send then to the Geometry service to union them.
Take the unioned geom and do the intersect using the individual user points

Re: Best way to select features within features

TimWitt2 — Fri, 17 Jul 2015 15:15:50 GMT

That is a great idea, I'll try that.

I just wish the javascript API had a similar tool like ArcGIS Desktop "Select by location"

Thanks!

Re: Best way to select features within features

TimWitt2 — Sat, 11 Dec 2021 07:19:46 GMT

One more question, how do I do step one?

I assume this happens here?

map.on('layer-add-result', function (evt){
    //What code do I need?
});

Re: Best way to select features within features

RobertScheitlin__GISP — Fri, 17 Jul 2015 15:39:43 GMT

Tim,

Can one assume that the layer has been added as a FeayureLayer and thus you will have access to the layer geometry without doing a QueryTask?

Re: Best way to select features within features

TimWitt2 — Fri, 17 Jul 2015 15:42:47 GMT

Yes, it will be a FeatureLayer.

Re: Best way to select features within features

RobertScheitlin__GISP — Sat, 11 Dec 2021 07:19:48 GMT

OK, then use this:

map.on('layer-add-result', function (evt){  
  var mp = new Multipoint();
  array.map(evt.layer.graphics, function(gra){
    mp.addPoint(gra.geometry);
  });
});