Merge pull request 'radius calculation for new panorama search based on latitude and mercator projection for google maps' (#36) from feature/more-accurate-new-selection-in-mapeditor-on-google-maps into develop

Reviewed-on: https://gitea.e5tv.hu/esoko/mapguesser/pulls/36
Reviewed-by: Pőcze Bence <bence@pocze.ch>

public/static/js/map_editor.js

@@ -86,7 +86,7 @@
             sv.getPanorama({
                 location: location,
                 preference: google.maps.StreetViewPreference.NEAREST,
-                radius: 100,
+                radius: MapEditor.map.getSearchRadius(location),
                 source: canBeIndoor ? google.maps.StreetViewSource.DEFAULT : google.maps.StreetViewSource.OUTDOOR
             }, function (data, status) {
                 var panoLocationData = status === google.maps.StreetViewStatus.OK ? data.location : null;
@@ -473,7 +473,11 @@
             LMapWrapper.markers.removeLayer(marker);
         },
 
-        toggleStreetViewCover: function () { }
+        toggleStreetViewCover: function () { },
+
+        getSearchRadius: function (location) {
+            return 100;
+        }
     };
 
     var GMapWrapper = {
@@ -626,6 +630,20 @@
                 GMapWrapper.streetViewCover.setMap(GMapWrapper.map);
                 GMapWrapper.streetViewCoverOn = true;
             }
+        },
+
+        getSearchRadius: function (location) {
+            // source: https://www.yorku.ca/mack/CHI01.htm
+            var movementOffset = 4;
+
+            // source: https://groups.google.com/g/google-maps-js-api-v3/c/hDRO4oHVSeM/m/osOYQYXg2oUJ?pli=1
+            var metersPerPixel = 156543.03392 * Math.cos(location.lat * Math.PI / 180) / Math.pow(2, GMapWrapper.map.getZoom());
+
+            var minSearchRadius = 5;
+
+            var searchRadius = Math.max(minSearchRadius, Math.round(movementOffset * metersPerPixel));
+
+            return searchRadius;
         }
     };