Using layered maps that overlap

LaurentG · June 21, 2024, 08:36:07 AM

I thought I've been clear about difference between Online and Offline maps. It seems it was not the case.

Offline map : An offline map is a file (a database) stored on your phone, that contains a limitative set of tiles , each of them corresponding to a square of land, at a specific zoom level. When you move the display to a position for which the corresponding tile is not in the database (at the requested zoom level), or (optionnally) when, without moving position, you change the requested zoom level to a level that is not in the database, OM looks for other offline maps present on your phone that contain the tile corresponding to this position, at the requested zoom level. At starting time, OM gathers in a synthetic way all information relative to content of each local (offline) map, allowing it to very quickly determine which map(s) contain the requested data.
If there is only one such map, OM automatically switch to this one, but if there are several offline maps on your phone that contain this tile, OM asks you which one you want to use.

Online map : An online map is served by an external server. Nothing resides on your phone, except parameters defining the server, and how to send requets to it. Some of these servers cover the full earth, some of them only a part of it.
OM sends an internet request to the server, specifying geographical position and zoom level. Afterwards, either the server is able to provide such data or not. But whatever the case, OM displays what it receives from the server, ie. either a tile of map, or an empty tile. From OM standpoint, we are never "outside geographical covering", nor at a "unavailable" zoom level.
Moreover, contrary to offline maps, OM cannot know in advance which pairs position/zoom level are actually available from each server, and then couldn't even suggest another online map in case current one returns an empty tile.

I hope it's more clear for you, now

YvanCB · June 21, 2024, 09:41:09 AM

Hello Laurent,

I really appreciate your help

!

I know the big difference between Online and Offline mode:
Online: Datas are on servers.
Offline: Datas are on the smartphone's memory card.

Therefor I'm sorry but something is still not clear for me. I still can't understand why OM manages to display images from the servers without any "pop-up".
How datas are organized on the servers so that everything is perfectly "smooth".

Do you think that the Online image distribution mode (via servers) could be used by OM with Offline maps?
If not (and I'm afraid it is), why

?

Regards.

LaurentG · June 21, 2024, 10:55:05 AM

Please read carefully what I wrote above, and try 1 second to think....
I'm afraid that I cannot explain more clearly.

The problem is NOT an "image distribution mode" issue (as you wrote, but these words do not even make sense, I'm sorry). The Difference is that local means a LIMITED set of tiles (a tile is a little part of the map, a square of 256x256 pixels, and map drawing is the assembly of tiles) : those that are NOT in the file are NOT in the file and OM cannot "invent" them, while online means a NON LIMITED (at least from OM standpoint) set of tiles.

The pop up appears ONLY :
- when the requested tile is NOT in the current map
- but is present in SEVERAL other local maps

If the requested tile is not in the current map but in exactly one other map, no pop-up, but rather automatic switch to this other map.
And if the requested tile is not in the current map nor in any other map, no pop-up as well.

LaurentG · June 21, 2024, 12:25:11 PM

Good news for you @YvanCB, there is actually a solution to avoid almost all pop-ups when map switching.

I just incidently discovered that something I asked for a long time ago... has been actually implemented in OM, and I didn't knew it.

As you know, offline map files can be organized in directories (or folders) and sub-directories. It is even recommended to do so.
And at map switching, folder of current map is somehow "priviledged".
In other words, it means that if the requested tile is NOT in the current map, but is present in ONLY one map belonging to the SAME folder than current map, OM switches automatically to this map, EVEN if one or several other maps own the requested tile BUT reside in ANOTHER folder.

Pop-up to choose the new map appears ONLY
- if there are SEVERAL maps owning the requested tile and stored in the SAME folder
- or there is NO map owning the tile and stored in the same folder BUT several maps owning the tile stored in another folder.

With an adequate organization of your maps in folders you should be able to avoid the pop-up in most of the cases.

YvanCB · June 21, 2024, 12:35:18 PM

QuoteThe pop up appears ONLY :
- when the requested tile is NOT in the current map
- but is present in SEVERAL other local maps

I completly agree with this.
If I don't want any pop-up I have to make sure that the tile to be displayed is only in one map.
This requires that there is no overlap area.
If I don't have overlapping another problem occurs : when OM comes at the edge of the map an "empty" area will then appear. This "empty" area will be there until the center of the screen is on this area and that OM switches to the other map.

It seems I'm looking for something that is impossible to obtain in Offline mode although it is obtainable in Online mode, isn't it?

Thank you Laurent, I don't want to disturb you, I just want to understand...

Regards.

LaurentG · June 21, 2024, 12:57:07 PM

Quote from: YvanCB on June 21, 2024, 12:35:18 PMI have to make sure that the tile to be displayed is only in one map.
This requires that there is no overlap area.

No, I disagree, this do NOT prevent you to have overlap area : tiles of overlap area are present in TWO maps. So if you are currently displaying one of these two maps, there is ONLY ONE other map with this tile...

Moreover , have a look to the post I did just while you were responding, and you have maybe missed, the #18 above

LaurentG · June 21, 2024, 01:01:57 PM

Quote from: YvanCB on June 21, 2024, 12:35:18 PMIt seems I'm looking for something that is impossible to obtain in Offline mode although it is obtainable in Online mode, isn't it?

Once more, in Online mode, there is no map switching, so you cannot compare both modes, and say what you say.

Moreover, with what I discovered and explained in post #18, you are actually "looking for something that is NOT impossible to obtain in Offline"

YvanCB · June 21, 2024, 01:50:52 PM

OK, Now it's really clear. I was trying to obtain something impossible to have.
Thank you for you help. Have a good day.

Regards.

LaurentG · June 21, 2024, 02:08:42 PM

Just one final remark : the mechanism of "folder privilege" at map switching applies ONLY to map switching due to position change, and NOT in case of Zoom change (when corresponding option is set). In this last case, all maps providing the zoom level for current position are proposed, whatever they are in the same folder than current map, or not.