Area calculation in planar with WebMercator polygon

JamesCrandall

JS 3.x

Before I got too far into this, wondering if anyone can point example of calculating more accurate acreage of input geometry of a web mercator aux sphere defined feature service?  I am currently determining acreage value calculations with  this function that implements esri.geometry.geodesicAreas but we see a discrepancy in values when we use ArcGIS Desktop and apply a planar projection to the same boundary.

getAcreageValueFromPolygon: function (geom) {
			  
			  var geometryService = new GeometryService("https://utility.arcgisonline.com/ArcGIS/rest/services/Geometry/GeometryServer");
			  var geographicGeometries = [];
			  //if self intersecting, simplify using geometry service
			  if (esri.geometry.polygonSelfIntersecting(geom)) {
				  //if self intersecting, simplify using geometry service
				  geometryService.simplify([geom], function (simplifiedGeometries) {
					  dojo.forEach(simplifiedGeometries, function (simplifiedGeometry, idx) {
						  geographicGeometries.push(esri.geometry.webMercatorToGeographic(simplifiedGeometry));
					  });
					  var areas = esri.geometry.geodesicAreas(geographicGeometries, esri.Units.ACRES);
					  acrevalue = new Number(areas[0]);
					  acrevalue = parseFloat(acrevalue.toPrecision(3));
				  });
			  }
			  else {
				  geographicGeometries.push(esri.geometry.webMercatorToGeographic(geom));
				  var areas = esri.geometry.geodesicAreas(geographicGeometries, esri.Units.ACRES);

				  acrevalue = new Number(areas[0]);
				  acrevalue = acrevalue.toPrecision(3);
			  }			  
			  return acrevalue
		  },