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diff --git a/gui/js/maps.js b/gui/js/maps.js
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+// Robinson projection calculation
+
+// Written by Niklas Bichinger (bichinger.de). This code is Public Domain - use as you like.
+
+// source of robinson numbers: https://simplemaps.com/static/img/flash/robinson_projection_table.jpg
+var robinsonAA = [
+    0.84870000,
+    0.84751182,
+    0.84479598,
+    0.84021300,
+    0.83359314,
+    0.82578510,
+    0.81475200,
+    0.80006949,
+    0.78216192,
+    0.76060494,
+    0.73658673,
+    0.70866450,
+    0.67777182,
+    0.64475739,
+    0.60987582,
+    0.57134484,
+    0.52729731,
+    0.48562614,
+    0.45167814
+];
+var robinsonBB = [
+    0.00000000,
+    0.08384260,
+    0.16768520,
+    0.25152780,
+    0.33537040,
+    0.41921300,
+    0.50305560,
+    0.58689820,
+    0.67047034,
+    0.75336633,
+    0.83518048,
+    0.91537187,
+    0.99339958,
+    1.06872269,
+    1.14066505,
+    1.20841528,
+    1.27035062,
+    1.31998003,
+    1.35230000
+];
+
+function project(latitude, longitude, mapWidth, heightFactor, mapOffsetX, mapOffsetY) {
+    if (typeof heightFactor === 'undefined') { heightFactor = 1; }
+    if (typeof mapOffsetX === 'undefined') { mapOffsetX = 0; }
+    if (typeof mapOffsetY === 'undefined') { mapOffsetY = 0; }
+
+    // Robinson's latitude interpolation points are in 5-degree-steps
+    var latitudeAbs = Math.abs(latitude);
+    var latitudeStepFloor = Math.floor(latitudeAbs / 5);
+    var latitudeStepCeil = Math.ceil(latitudeAbs / 5);
+    // calc interpolation factor (>=0 to <1) between two steps
+    var latitudeInterpolation = (latitudeAbs - latitudeStepFloor * 5) / 5;
+
+    // interpolate robinson table values
+    var AA = robinsonAA[latitudeStepFloor] + (robinsonAA[latitudeStepCeil] - robinsonAA[latitudeStepFloor]) * latitudeInterpolation;
+    var BB = robinsonBB[latitudeStepFloor] + (robinsonBB[latitudeStepCeil] - robinsonBB[latitudeStepFloor]) * latitudeInterpolation;
+
+    var robinsonWidth = 2 * Math.PI * robinsonAA[0];
+    var widthFactor = mapWidth / robinsonWidth;
+    var latitudeSign = Math.sign(latitude) || 1;
+    var x = (widthFactor * AA * longitude * Math.PI) / 180 + mapOffsetX;
+    var y = widthFactor * BB * latitudeSign * heightFactor + mapOffsetY;
+
+    return {x: x, y: y};
+}
+
+function projectAbsolute(latitude, longitude, mapWidth, heightFactor, mapOffsetX, mapOffsetY) {
+    if (typeof heightFactor === 'undefined') { heightFactor = 1; }
+
+    var relative = project(latitude, longitude, mapWidth, heightFactor, mapOffsetX, mapOffsetY);
+    var widthHeightRatio = Math.PI * robinsonAA[0] / robinsonBB[18];
+    var x = mapWidth / 2 + relative.x;
+    var y = mapWidth / widthHeightRatio * heightFactor / 2 - relative.y;
+
+    return {x: x, y: y};
+}