gis - Specifying Lat & Long for Leaflet TileLayer

Question

Seems like a simple question, but I have been tearing my hair out for hours now.

I have a series of files ie.

kml_image_L1_0_0.jpg
kml_image_L2_0_0.jpg
kml_image_L2_0_1.jpg
kml_image_L2_1_0.jpg
kml_image_L2_1_1.jpg

etc. However just plotting them on the leaflet map surface understandibly puts the images at 0,0 on the earths surface, and the 0 zoom level inferred by the files should really be about 15 or so.

So I want to specify the latitude and longitude where the images should originate , and what zoom level they should start at. I have tried bounds (which doesn't display anything) and I have tried playing with offsetting the zoom level.

I need this because a user needs to click on an offline map to specify where they are and I need the GPS coordinates.

I also have a KML file but it seems to be of more help for plotting vector data on the map.

Any help is much appreciated, cheers.

Answer 1

If I understand correctly, the "kml_image_Lz_x_y.jpg" images that you have are actually tiles, with zoom, horizontal and vertical indices in their file name?

And your issue is that they use (z,x,y) numbers as if they started from the top-most level (zoom 0, single tile for entire world), but in fact they are just a small portion of the pyramid of tiles?

And you cannot use them as is because you still want to get actual geographic coordinates (latitude, longitude), which would be totally wrong if you used the tiles as if they were showing the entire world?

In that case, you have several options as workarounds:

The most simple and reliable would probably be to simply write a small script to rename all your tiles to their true (z,x,y) numbers.

Another option would be to modify the (z,x,y) numbers before they are written in the tile src attribute, and apply the appropriate offset (constant for z, scaled by z for x and y). That should probably happen in L.TileLayer.getTileUrl() method.

Good luck! :-)