fix scale calculation for non-metric projection (#406)

open-pioneer · Feb 24, 2025 · e7fdc5d · e7fdc5d
1 parent bce31b4
commit e7fdc5d
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diff --git a/.changeset/cuddly-monkeys-do.md b/.changeset/cuddly-monkeys-do.md
@@ -0,0 +1,8 @@
+---
+"@open-pioneer/map": minor
+---
+
+improve scale calculation for none-metric projections
+
+Fix scale calculation for projections with none-metric units (e.g. EPSG:4326).  
+Note: The calculated scale (`useScale`) still may deviate from the desired scale (`setScale`) for non-metric projections. This is due to limitiations in the [getPointResolution](https://openlayers.org/en/latest/apidoc/module-ol_proj.html#.getPointResolution) function from OL.
diff --git a/src/packages/map/model/MapModelImpl.ts b/src/packages/map/model/MapModelImpl.ts
@@ -118,7 +118,7 @@ export class MapModelImpl extends EventEmitter<MapModelEvents> implements MapMod
              * Returns the appropriate scale for the given resolution and units, see OpenLayers function getScaleForResolution()
              * https://github.com/openlayers/openlayers/blob/7fa9df03431e9e1bc517e6c414565d9f848a3132/src/ol/control/ScaleLine.js#L454C3-L454C24
              */
-            const pointResolution = getPointResolution(projection, resolution, center);
+            const pointResolution = getPointResolution(projection, resolution, center, "m"); //point resolution in meter per pixel
             const scale = Math.round(pointResolution * INCHES_PER_METRE * DEFAULT_DPI);
             return scale;
         });

diff --git a/src/packages/map/ui/hooks.ts b/src/packages/map/ui/hooks.ts
@@ -99,7 +99,7 @@ export function useScale(map: OlMap | undefined): number | undefined {
          * Returns the appropriate scale for the given resolution and units, see OpenLayers function getScaleForResolution()
          * https://github.com/openlayers/openlayers/blob/7fa9df03431e9e1bc517e6c414565d9f848a3132/src/ol/control/ScaleLine.js#L454C3-L454C24
          */
-        const pointResolution = getPointResolution(projection, resolution, center);
+        const pointResolution = getPointResolution(projection, resolution, center, "m"); //point resolution in meter per pixel
         const scale = Math.round(pointResolution * INCHES_PER_METRE * DEFAULT_DPI);
         return scale;
     }, [projection, resolution, center]);