[GIS] Check if lat/long point is within shape

arcgis-javascript-api

I'm a bit new to ESRI and GIS so forgive me if this is a simple question.

Looking at this example ESRI Javascript sample (source code is here) I see you can click on a shape (via a published shape file) and if the point upon which you click is within a shape an action fires.

Is it possible to send a lat/long via some mechanism and IF that lat/long is within the shape the same (or similar) action fires?

Can I see if a lat/long is contained within ANY polygon that is contained in a published shapefile.

If my understanding of the ESRI javascript API is correct the point that the mouse is clicked does translate to a lat/long location.

Best Answer

If both your polygon and point geometry objects are on the client side, you can use the Polygon.contains() method

Related Solutions

[GIS] Draw a point with ArcGIS Javascript API

Adding a point from a button click can be as simple as:

dojo.connect(dojo.byId('pointButton'), 'onclick', function() {
  map.graphics.add(new esri.Graphic(
    // Point coordinates are 0, 0
    new esri.geometry.Point(0, 0, map.spatialReference),
    new esri.symbol.SimpleMarkerSymbol()
  ));
});

And the pointButton node is:

<button id="pointButton">Click to add a point.</button>

To add a point when the map is clicked is pretty straightforward as well:

dojo.connect(map, 'onClick', function(evt) {
  map.graphics.add(new esri.Graphic(
    evt.mapPoint,
    new esri.symbol.SimpleMarkerSymbol()
  ));
});

Live example showing both here: http://jsfiddle.net/swingley/auyHf/

Regarding converting from lat, long to another coordinate system: if you're converting to or from lat, long to web mercator, there are client side methods available to do this: esri.geometry.geographicToWebMercator and esri.geometry.WebMercatorToGeographic. If you need to convert from lat, long to something other than web mercator, then the geometry service's project method is the way to go.

[GIS] ArcGIS JS Api: Getting information by location from multiple layers

When using the Javascript api, a good way to pull off what you're asking is to query the cities layer, and in the callback for the cities query, query the countries layer using the same geometry. To do that, you'll either need to store the clicked geometry and the results, or nest the queries. Here's an example of the nested query:

dojo.connect(map, "onClick", function (evt) {
  var cityQuery = new esri.tasks.QueryTask("http://mymaps.com/arcgis/rest/services/world/MapService/0");
  var cityParams = new esri.tasks.Query();

  //...set parameters
  cityParams.geometry = evt.mapPoint;

  cityQuery.execute(cityParams, function (cityResults) {
     // function runs when browser receives query results from city layer.

     var countryQuery = esri.tasks.QueryTask("http://mymaps.com/arcgis/rest/services/world/MapService/1");
     var countryParams = new esri.tasks.Query();

     // ... set country query parameters
     countryParams.geometry = evt.mapPoint; //from the previous click

     countryQuery.execute(countryParams, function (countryResults) {

       // this function runs when browser receives query results from country layer
       var allAttributes = {};

       if (cityResults.features.length > 0) {
         // add city results if there are any
       }

       if (countryResults.features.length > 0) {
         // add country results if there are any
       }

       // show results here
     });
   });
 });

Best Answer

Related Solutions

[GIS] Draw a point with ArcGIS Javascript API

[GIS] ArcGIS JS Api: Getting information by location from multiple layers

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