Merged PR 122160: Reduce threshold where GCS is used to calculate lin…

…ear map transform.

When displaying background map we need a linear transform from the BIM coordinates to ECEF -- This is stored as the ECEF location --unfortunately this is not always valid and is not reset after being miscalculated in bridge.   In the case where there is a GCS we can calculate a valid transform - but currently this was only done if project more than 100KM from earth -- reduced this to 5KM -- It should probably be even tighter but will reserve that for future.

common/changes/@bentley/imodeljs-frontend/Refine-ECEF-validation-when-calculating-background-map-location-_2020-10-23-12-06.json

@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "packageName": "@bentley/imodeljs-frontend",
+      "comment": "Reduce threshold for ecef validation.",
+      "type": "none"
+    }
+  ],
+  "packageName": "@bentley/imodeljs-frontend",
+  "email": "[email protected]"
+}

core/frontend/src/BackgroundMapGeometry.ts

@@ -387,7 +387,9 @@ export class BackgroundMapLocation {
 
     const ecefOriginTest = ecefLocationDbToEcef.multiplyPoint3d(origin);
     const cartoOriginTest = Cartographic.fromEcef(ecefOriginTest);
-    if (cartoOriginTest !== undefined && Math.abs(cartoOriginTest.height) < 1.0E5) {
+    // If the project center is within 5KM of the ellipsoid then assume that the existing ECEF is valid.  Otherwise recalculate
+    // from the GCS.
+    if (cartoOriginTest !== undefined && Math.abs(cartoOriginTest.height) < 5.0E3) {
       this._ecefValidated = true;     // ECEF looks reasonable - use it...
       return;
     }