Problem (bug ?) with Multimaps

[LaurentG]

Hi Orux,



when creating a "multimap" blending two maps with exactly the same coverage, everything works fine. In particular, the "multiply" option is very good to add over any map the "paths" issued from WayMarkedTrails, provided we extract them with a white background.



But in case the different layers do not have exactly the same coverage, at some zoom levels, multimap is OK, but at some other, the second layer is not correctly displayed : most of the time, it is only displayed with a lateral or vertical lag, as if calibration data of the layer were not correct, but sometimes, it becomes almost "crazy" (as in the example below)

Of course, the different "layers", even if they do not have exactly the same coverage, are using same "projection" and have same available zoom levels.



Is it a know bug, or known limitation of Multimap ?

Actually, it makes quite impossible to use this feature, since most of the time, the different layers have not been generated at the same time (in MOBAC), and then do not have exactly the same coverage.



Hereafter an example (created to illustrate)

Here is the coverage of the "ground" layer (FYI, it is "Ile d'Yeu", in France, in front of Nantes. Map from OSM, zoom 14, 15 & 16))

https://images2.imgbox.com/dc/d0/EfQwT6Te_o.png">



Here is the coverage of the "top" layer, coming from WayMarkedTrails / Hiking paths, same zoom levels)

https://images2.imgbox.com/9f/57/gOO0I4Ke_o.png">



At level 16, display is fine

https://images2.imgbox.com/61/33/k6dJ813j_o.png">



At level 15, OK also

https://images2.imgbox.com/c2/9f/kteSnVD2_o.png">



But at level 14  

https://images2.imgbox.com/80/58/r2tX5MYL_o.png">

[orux]

Hi Orux,



when creating a "multimap" blending two maps with exactly the same coverage, everything works fine. In particular, the "multiply" option is very good to add over any map the "paths" issued from WayMarkedTrails, provided we extract them with a white background.



But in case the different layers do not have exactly the same coverage, at some zoom levels, multimap is OK, but at some other, the second layer is not correctly displayed : most of the time, it is only displayed with a lateral or vertical lag, as if calibration data of the layer were not correct, but sometimes, it becomes almost "crazy" (as in the example below)

Of course, the different "layers", even if they do not have exactly the same coverage, are using same "projection" and have same available zoom levels.



Is it a know bug, or known limitation of Multimap ?

Actually, it makes quite impossible to use this feature, since most of the time, the different layers have not been generated at the same time (in MOBAC), and then do not have exactly the same coverage.

Hello!



The map format of the composed maps?



If you use mbtiles format, they should work fine.



If you are using oruxmaps format, yes, it is possible the bug. If you can share the maps, I can test,





orux

[LaurentG]

Hi Orux,



thank you for answer.



Yes, my maps (like all maps I generate using Mobac for OruxMaps) are in OruxMaps/sqlite format.

Actually, I didn't even know that other formats were OK for OruxMaps  



And also I confirm : I regenerate them in Mbtiles format to replicate the test, and in this format, it works fine.



Nevertheless, I'd prefer to stay in OruxMaps format (otherwise I'd have to re-generate all my maps database, since it's not even feasible to combine one layer in OruxMaps format, and the other in MBTiles....), and so, if you may have a look : maps I used  in this example are available here : http://dl.free.fr/rH3pK9bw7">http://dl.free.fr/rH3pK9bw7 (~3Mb)



Many thanks in advance

Regards

Laurent