feat: zoomToResDeg and zoomToResMeter

src/geo/tiles.ts

@@ -2,6 +2,58 @@ import { BBox2d } from '@turf/helpers/dist/js/lib/geojson';
 import { ITile } from '../models/interfaces/geo/iTile';
 import { tileToDegrees } from './geoConvertor';
 
+const zoomToResolutionDegMapper: Record<number, number> = {
+  0: 0.703125,
+  1: 0.3515625,
+  2: 0.17578125,
+  3: 0.087890625,
+  4: 0.0439453125,
+  5: 0.02197265625,
+  6: 0.010986328125,
+  7: 0.0054931640625,
+  8: 0.00274658203125,
+  9: 0.001373291015625,
+  10: 0.0006866455078125,
+  11: 0.00034332275390625,
+  12: 0.000171661376953125,
+  13: 0.0000858306884765625,
+  14: 0.0000429153442382812,
+  15: 0.0000214576721191406,
+  16: 0.0000107288360595703,
+  17: 0.00000536441802978516,
+  18: 0.00000268220901489258,
+  19: 0.00000134110450744629,
+  20: 0.000000670552253723145,
+  21: 0.000000335276126861572,
+  22: 0.000000167638063430786,
+};
+
+const zoomToResolutionMeterMapper: Record<number, number> = {
+  0: 78271.52,
+  1: 39135.76,
+  2: 19567.88,
+  3: 9783.94,
+  4: 4891.97,
+  5: 2445.98,
+  6: 1222.99,
+  7: 611.5,
+  8: 305.75,
+  9: 152.87,
+  10: 76.44,
+  11: 38.22,
+  12: 19.11,
+  13: 9.55,
+  14: 4.78,
+  15: 2.39,
+  16: 1.19,
+  17: 0.6,
+  18: 0.3,
+  19: 0.15,
+  20: 0.075,
+  21: 0.037,
+  22: 0.0185,
+};
+
 /**
  * calculates tile size (resolution) in degrees
  * @param zoomLevel zoom level of returned tile size
@@ -37,6 +89,24 @@ export function flipYAxis(tile: ITile): ITile {
   };
 }
 
+/**
+ * converts zoom level (integer) to matching resolution degree value
+ * @param zoom zoom level in range of 0-22
+ * @returns resolution represented in degrees, or undefined if zoom level is out of range
+ */
+export function zoomLevelToResolutionDeg(zoom: number): number | undefined {
+  return zoomToResolutionDegMapper[zoom];
+}
+
+/**
+ * converts zoom level (integer) to matching resolution meter value
+ * @param zoom zoom level in range of 0-22
+ * @returns resolution represented in Meters, or undefined if zoom level is out of range
+ */
+export function zoomLevelToResolutionMeter(zoom: number): number | undefined {
+  return zoomToResolutionMeterMapper[zoom];
+}
+
 /**
  * converts pixel size (resolution) in degrees to matching zoom level (rounded down)
  * @param resolution pixel size (resolution) in degrees

tests/unit/geo/tiles.spec.ts

@@ -1,4 +1,11 @@
-import { degreesPerPixel, degreesPerPixelToZoomLevel, degreesPerTile, flipYAxis } from '../../../src/geo/tiles';
+import {
+  degreesPerPixel,
+  degreesPerPixelToZoomLevel,
+  degreesPerTile,
+  flipYAxis,
+  zoomLevelToResolutionDeg,
+  zoomLevelToResolutionMeter,
+} from '../../../src/geo/tiles';
 
 describe('tiles', () => {
   describe('degreesPerTile', () => {
@@ -59,4 +66,42 @@ describe('tiles', () => {
       expect(zoomLevelResult).toEqual(22);
     });
   });
+
+  describe('zoomLevelToResolutionDeg', () => {
+    it('Check calculation for min zoom level 0', function () {
+      const resolutionDegResult = zoomLevelToResolutionDeg(0);
+      const expectedResult = 0.703125;
+      expect(resolutionDegResult).toEqual(expectedResult);
+    });
+
+    it('Check calculation for max zoom level 22', function () {
+      const resolutionDegResult = zoomLevelToResolutionDeg(22);
+      const expectedResult = 0.000000167638063430786;
+      expect(resolutionDegResult).toEqual(expectedResult);
+    });
+
+    it('Check for return undefined value for out of range value', function () {
+      const resolutionDegResult = zoomLevelToResolutionDeg(50);
+      expect(resolutionDegResult === undefined).toEqual(true);
+    });
+  });
+
+  describe('zoomLevelToResolutionMeter', () => {
+    it('Check calculation for min zoom level 0', function () {
+      const resolutionDegResult = zoomLevelToResolutionMeter(0);
+      const expectedResult = 78271.52;
+      expect(resolutionDegResult).toEqual(expectedResult);
+    });
+
+    it('Check calculation for max zoom level 22', function () {
+      const resolutionDegResult = zoomLevelToResolutionMeter(22);
+      const expectedResult = 0.0185;
+      expect(resolutionDegResult).toEqual(expectedResult);
+    });
+
+    it('Check for return undefined value for out of range value', function () {
+      const resolutionDegResult = zoomLevelToResolutionMeter(50);
+      expect(resolutionDegResult === undefined).toEqual(true);
+    });
+  });
 });