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How to calculate geodesic area of polygons on map

rsharma

Hi i want to calculate area of polygons drawn on map geometry, any arcgis sample will be helpful

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Accepted answers

RobertScheitlin__GISP

Rajni,

A ring is just an array of coordinate and not an actual geometry class thus the geodesicArea method is failing.

Here is what you need to do instead.

      <SPAN class="keyword token">function</SPAN> <SPAN class="token function">calculateArea</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="punctuation token">{</SPAN>
        <SPAN class="keyword token">var</SPAN> area <SPAN class="operator token">=</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">;</SPAN>
        graphicsLayer<SPAN class="punctuation token">.</SPAN>graphics<SPAN class="punctuation token">.</SPAN><SPAN class="token function">map</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="keyword token">function</SPAN> <SPAN class="punctuation token">(</SPAN>grap<SPAN class="punctuation token">)</SPAN> <SPAN class="punctuation token">{</SPAN>
          area <SPAN class="operator token">=</SPAN> geometryEngine<SPAN class="punctuation token">.</SPAN><SPAN class="token function">geodesicArea</SPAN><SPAN class="punctuation token">(</SPAN>grap<SPAN class="punctuation token">.</SPAN>geometry<SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"hectares"</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
        <SPAN class="punctuation token">}</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
        console<SPAN class="punctuation token">.</SPAN><SPAN class="token function">log</SPAN><SPAN class="punctuation token">(</SPAN>area<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
      <SPAN class="punctuation token">}</SPAN> <SPAN class="comment token">//End calculateArea‍‍‍‍‍‍‍</SPAN><SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

All comments

rsharma

Do i need to convert them rings_for_area to webMercatorUtils.geographicToWebMercator, Ok i have converted it and now it returns 0 area value, even when i have a polygon on map

UndralBatsukh

Check out this test app to see how it works. Hopefully, it will point you to a right direction.

-Undral

rsharma

Hi ken, this time i summed it up but due to this bolded code to calculate area, my whole map stops working. No error in console even. No area consoled even.

kenbuja

You have a scope problem. Since the variable rings_for_area is declared inside the map function, it's not available outside the function. Why aren't you calculating the area of the rings inside the map function and summing that up?

rsharma

Hi Noah , I m trying to get geometry of all polygons from a map with below code, but doen't get rings area in console.

function calculateArea(){
         graphicsLayer.graphics.map(function(grap){
          var updatedGeometry = webMercatorUtils.webMercatorToGeographic(grap.geometry);
          var rings_for_area = updatedGeometry.rings;
          console.log(rings_for_area);//return all rings
         });
        var area = geometryEngine.geodesicArea(rings_for_area, "hectares");
        console.log(area);//doesn't return area
       }

Noah Sager

There is also a lot of good information inside the GeometryEngine class:

geometryEngine | ArcGIS API for JavaScript 4.14

BenElan

Take a look at the measure widget: Measurement in 2D | ArcGIS API for JavaScript 4.14

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