AlpineQuest & OfflineMaps

I want to convert the OS GB 1:25,000 maps to use them with AlpineQuest. They are cached in MOBAC so can be converted to anything through that. I have already converted them to JNX format for my Garmin (OSMTracker atlas to JNX using mobat2jnx).

On a small test region, I created both a JNX and an AQM file. The JNX file was about 13MB and the AQM file was about 55MB. That's over four times larger for the AQM file.

I guess that is due to the png versus jpg images that JNX uses.

Is there any way to make the AQM files smaller?

At the current rate there is no way that I can fit my maps onto the available storage in AQM format. I would need to split them over four 32GB cards. My JNX and (older*) QCT maps easily fit a single card.

*My QCT maps originally bought for memory map are of date otherwise I would just use them.

I think I've partially answered this myself. I missed that MOBAC can re-sample the map tiles and save them in jpeg format. This has produced smaller AQM files and a quick test on my phone gave good results.

Unfortunately MOBAC seems to want to reload all the map tiles instead of using what it has in the cache if I do this... seems to be a MOBAC thing though, nothing to do with AplineQuest. That's a lot of data do re-download!

I'll see if I can find a workaround for that.

Hi,

Yes you can re-sample data using MOBAC to convert it in JPG format as you've found.

However I just made a test using the re-sample option with already cached data and it seems to work fine, here is how I proceeded:
- with PC online, I cached an area on MOBAC, few zoom levels;
- I disabled the WiFi, checked that MOBAC could not retrieve new parts of the map;
- I selected a stored area and made an AQM map without processing, it worked fine (file of 4.1MB);
- I configured a re-sample (JPG 50%, 128x128 pix tiles), applied it to the atlas;
- I re-started the map creation, it worked fine again (file of 114.1KB!).

Both maps are ok in the app, although the second one is not really readable.
I used MOBAC 1.9.16.

Let me know if I can do something else to help
Best regards

Thanks for the reply and workaround for MOBAC.

Using a jpeg quality of 80 gives me a good balance of image quality and file size, so I'll go with that.

My plan is to do the whole of GB in 1:25000, like I have in QCT and JNX. How am I best doing that with the AQM format for AlpineQuest? Is there a hard size or tile limit for each file, or an optimum tile size, for instance? I'm just fishing for hints before I spend a few days on it, lol.

You should avoid too larger maps (> 2GB) as it may not work properly on some devices.
I also generally recommend to split the data by area rather that zoom levels, so you may create different maps for different parts of the country, all with all the zoom levels you want. In this case you'll less have to load new maps.
But it's really up to you.

Don't hesitate if you have any question
Best regards