I am working on a solution to download map tiles based on given location:(latitude, longitude) and zoom level
Followed https://wiki.openstreetmap.org/wiki/Slippy_map_tilenames
The key concept is to convert (latitude, longitude) to tile reference, eg. javascript code:
function long2tileX(lon,zoom) { return (Math.floor((lon+180)/360*Math.pow(2,zoom))); }
function lat2tileY(lat,zoom) { return (Math.floor((1-Math.log(Math.tan(lat*Math.PI/180) + 1/Math.cos(lat*Math.PI/180))/Math.PI)/2 *Math.pow(2,zoom))); }
For sample location (63.433772, 10.393456) and zoom level (17) this formulas return (69320, 35421) which is exactly what's needed to get the tile:
https://opencache.statkart.no/gatekeeper/gk/gk.open_gmaps?layers=topo4&zoom=17&x=69320&y=35421
Now I am struggling to achieve the same with ArcGIS maps. The following CRS object is supplied:
{
"Name":"Geocache Basis",
"Crs":{
"Resolutions":[
21674.7100160867,
10837.355008043351,
5418.6775040216753,
2709.3387520108377,
1354.6693760054188,
677.33468800270941,
338.66734400135471,
169.33367200067735,
84.666836000338677,
42.333418000169338,
21.166709000084669,
10.583354500042335,
5.2916772500211673,
2.6458386250105836,
1.3229193125052918,
0.66145965625264591,
0.33072982812632296,
0.16536491406316148
],
"OriginX":-2500000.0,
"OriginY":9045984.0,
"Srid":"EPSG:32633",
"Definition":"+proj=utm +zone=33 +ellps=WGS84 +datum=WGS84 +units=m +no_defs"
},
"Attribution":"Kartverket, Geovekst og kommuner - Geodata AS",
"MapProvider":"arcgis"
}
Tried to use proj4 and define EPSG:32633 with 'Definition' field value, then do a projection, but that didn't get me anywhere close to calculating the respective tile coordinates, which I experimentally determined to be (47333, 65439) https://services.geodataonline.no/arcgis/rest/services/Geocache_UTM33_WGS84/GeocacheBasis/MapServer/tile/17/47333/65439
I'd appreciate any hint on what mathematical formula I can apply to follow the same scenario and get the accurate result.
