Add another zoom level to worldimagery

Author: Mark Jessop

js/tracker.js

@@ -419,7 +419,9 @@ var dark_matter = L.tileLayer('https://{s}.basemaps.cartocdn.com/dark_all/{z}/{x
 dark_matter.id="DarkMatter";
 
 var worldimagery = L.tileLayer('https://server.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer/tile/{z}/{y}/{x}', {
-	attribution: 'Tiles © Esri — Source: Esri, i-cubed, USDA, USGS, AEX, GeoEye, Getmapping, Aerogrid, IGN, IGP, UPR-EGP, and the GIS User Community'
+	attribution: 'Tiles © Esri — Source: Esri, i-cubed, USDA, USGS, AEX, GeoEye, Getmapping, Aerogrid, IGN, IGP, UPR-EGP, and the GIS User Community',
+    minZoom: 0,
+	maxZoom: 19,
 });
 worldimagery.id="WorldImagery";