Hello there,
I have a question regarding the creation of the WMTS server requests.
From this german governmental-website:https://www.bezreg-koeln.nrw.de/brk_internet/geobasis/luftbilderzeugnisse/digitale_orthophotos/index.html I can get the address for their WMTS server: https://www.wmts.nrw.de/geobasis/wmts_nw_dop. I can successfully integrate it into josm as an image layer (wmts:https://www.wmts.nrw.de/geobasis/wmts_nw_dop) and it gets displayed correctly.
I can watch the server request made by josm in the terminal, which is something like:
2019-09-26 18:54:31.651 INFO: GET https://www.wmts.nrw.de/geobasis/wmts_nw_dop/tiles/nw_dop/EPSG_25832_16/16/17680/35107 -> HTTP_1 200 (13.3 kB)
You can view this tile @https://www.wmts.nrw.de/geobasis/wmts_nw_dop/tiles/nw_dop/EPSG_25832_16/16/17680/35107
Now I want to know how these requests are created, because for another project(which uses this library:https://github.com/gareth-cross/rviz_satellite) I need the string for the request in the format:
https://www.wmts.nrw.de/geobasis/wmts_nw_dop/tiles/nw_dop/EPSG_25832_16/{z}/{y}/{x}
If I let the library figure out the y and x, I’m getting trash in rviz(which is the visualization program):
I think this is because the images/tiles are in EPSG25832-projection method, but the library thinks in Mercator-projection. And I need the images to be in EPSG25832, because of other data which gets displayed.
If you look at the WMTSCapabilities.xml of the map-server you can see there are images avaible up to zoom level 16 and other info:
https://www.wmts.nrw.de/geobasis/wmts_nw_dop/tiles/nw_dop/EPSG_25832_16/1.0.0/WMTSCapabilities.xml
I had a look at the methods, which the library seems to use to calculate the x and y:
https://wiki.openstreetmap.org/wiki/Slippy_map_tilenames#Lon…2Flat._to_tile_numbers
which is something like this:
// in Coordinates.h:
int const n = 1 << zoom;
double x = n * ((coord.lon + 180) / 360.0);
double y = n * (1 - (std::log(std::tan(lat_rad) + 1 / std::cos(lat_rad)) / M_PI)) / 2;
But I think I need to do something like this, because of the EPSG25832/UTM projection:
https://en.wikipedia.org/wiki/Transverse_Mercator_projection
I already had a look at https://josm.openstreetmap.de/doc/org/openstreetmap/gui/jmapviewer/Tile.html to see how openstreetmap does it, but I didn’t find anything.
So all in all: How to calculate the x,y-tile-coordinates from lat,long if given images in EPSG25832-projection method (which josm/osm does succesfully)?