Possible to show features of a LoMap at any zoom level via theme?

Started by gauvins, October 25, 2021, 23:34:36

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Poco F5, Android 13 / Xiaomi Redmi Note 10 Pro, Android 13
Locus Map 4 Gold (always latest version or Beta)
LM4 User-ID: 11cec7cb5  (Devices-ID poco F5)


QuoteMy understanding is that it would be possible to extract map data with every feature appearing at zoom 0, and to defer rendering at a given zoom level to the xml (theme) instructions. I

Theoretically, it's possible if you generate your own maps. By default, the generated map (LoMaps) consists of 3 inner parts - zoom levels.
see 'zoom-interval-conf' parameter at https://github.com/mapsforge/mapsforge/blob/master/docs/Getting-Started-Map-Writer.md

The goal is to limit the number of elements in small zooms to avoid slow rendering.  The question is whether it is even a good idea to render small road lines below level < 12. I think the number of roads would be large and the map would become unreadable.


Quote from: voldapet on November 02, 2021, 09:54:39
[ The question is whether it is even a good idea to render small road lines below level < 12. I think the number of roads would be large and the map would become unreadable.

I understand your point. However in parts of the world, there are few roads of any size, and small scale is all but necessary. Take Australia. Even on a large computer screen, using Google Maps, figuring out options to travel from Uluru to Little Sandy Desert without a routing software is all but impossible. In Locus, after quite a bit of zooming in/out in order to locate reasonable endpoints, bRouter will come up with a suggestion that you'll have to follow more or less blindly because there is no way to visualize alternatives.

Same issue in Northern Canada (where I live) and, I assume, the stans/Mongolia,. large portions of South America and Africa...

Anyhow -- I think it would be great if the map file didn't make rendering assumptions. I'll try to find the time to generate an agnostic map and see if there is any performance issue when these instructions are located in the theme.

Or may I tempt you in generating a map set for Australia (and Canada) and I'll let you know how things went on my cheap, yet beloved, e-ink phone? :)


For OAM Christian uses different base settings for different parts of the world to exactly address the problem you are highlighting. The elements theme is the right counterpart for those areas of the world.
Give it a try.

Looking at Canada OSM data, there is also TONS of work to do for the OSM mappers :-)


Thanks for the nudge.

I've installed an OAM map. On the plus side, it looks as if features can be displayed at a smaller scale. Unfortunately the General/Element/Elevate themes do not render very well on an e-ink device and it is not clear how I can make my theme work. I've tried putting the xml file inside the _themes/Elevate folder, to no avail. I've also tried to replace the Elevate.xml with my theme and still no love.

I'll examine the Elevate and try to understand what breaks.

Will eventually update on this thread.

Thanks again


Maybe this one  (see attached) is a good start?
I did not try, but remembered the other thread about this subject.


Good luck and cheers



Well -- I think I am giving up on OAM. Yes, their themes are excellent, but they do not render well in gray scale. My version of a B&W theme didn't work out of the box" I think that it is because I am using html color names -- black instead of #000000 -- which breaks rendering (!?). A brief experiment suggested that features rendering is also limited by the zoom level, so there isn't much room for improving my use case.

BTW -- I am able to reasonably see routing options between Uluru and Little Sandy Desert, which is good  enough for me :)

I'll eventually get back to this idea when I have more free time on my hands.

Thanks again for your input