Add statia maps

Author: Mark Jessop

js/tracker.js

@@ -585,12 +585,12 @@ var worldimagery = L.tileLayer('https://server.arcgisonline.com/ArcGIS/rest/serv
 });
 worldimagery.id="WorldImagery";
 
-var stamen_terrain = L.tileLayer('https://stamen-tiles-{s}.a.ssl.fastly.net/terrain/{z}/{x}/{y}{r}.png', {
-	attribution: 'Map tiles by <a href="http://stamen.com">Stamen Design</a>, <a href="http://creativecommons.org/licenses/by/3.0">CC BY 3.0</a> &mdash; Map data &copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors',
-	subdomains: 'abcd',
-	minZoom: 0,
-	maxZoom: 18,
+var stamen_terrain = L.tileLayer('https://tiles.stadiamaps.com/tiles/stamen_terrain/{z}/{x}/{y}{r}.png', {
+    minZoom: 0,            
+    maxZoom: 20,
+    attribution: '&copy; <a href="https://stadiamaps.com/" target="_blank">Stadia Maps</a>, &copy; <a href="https://openmaptiles.org/" target="_blank">OpenMapTiles</a> &copy; <a href="https://www.openstreetmap.org/about" target="_blank">OpenStreetMap</a> contributors',
 });
+
 stamen_terrain.id="Terrain";
 
 var cartodb_voyager = L.tileLayer('https://{s}.basemaps.cartocdn.com/rastertiles/voyager/{z}/{x}/{y}{r}.png', {