Add isolines for Alaska

[person142]

Is your feature request related to a problem? Please describe.
Isolines are disabled for Alaska - this appears to be because of size constraints:

#4580 (comment)

Describe the solution you would like
Isolines enabled for Alaska - or at least some parts of it.

Describe alternatives you have considered
I use other maps for topographical data.

Additional context
A lot of hiking in Alaska is off-trail, so without topographical data you're flying pretty blind. For example, a commonly-climbed off-trail peak around Anchorage is Mount Williwaw:

https://omaps.app/0oznse0M59/Mount_Williwaw

and the map is largely blank for that area.

I'm happy to make PRs to get Alaska supported, though I'm not sure how deep the rabbit hole goes with the space tradeoffs needed. For Alaska in particular I'd guess that people would happily accept a larger map size in exchange for isolines.

[pastk]

@vng

[vng]

I tried a useless poor profile (500m) before and the size increase was insane (something like 150 -> 300 Mb)
Probably, we can try to turn on isolines for some parts (tiles) only ..

[person142]

Some interesting bounding boxes:

The national parks

• Denali national park: https://nominatim.openstreetmap.org/search.php?q=denali+national+park&format=jsonv2
• Gates of the Arctic national park: https://nominatim.openstreetmap.org/search.php?q=gates+of+the+arctic+national+park&format=jsonv2
• Glacier bay national park: https://nominatim.openstreetmap.org/search.php?q=glacier+bay+national+park&format=jsonv2
• Katmai national park: https://nominatim.openstreetmap.org/search.php?q=katmai+national+park&format=jsonv2
• Kenai Fjords national park: https://nominatim.openstreetmap.org/search.php?q=kenai+fjords+national+park&format=jsonv2
• Kobuk Valley national park: https://nominatim.openstreetmap.org/search.php?q=kobuk+valley+national+park&format=jsonv2
• Lake Clark national park: https://nominatim.openstreetmap.org/search.php?q=lake+clark+national+park&format=jsonv2
• Wrangell St Elias national park: https://nominatim.openstreetmap.org/search.php?q=Wrangell+-+St+Elias+national+park&format=jsonv2

The state parks (that I could find OSM bounding boxes for)

• Chugach state park: https://nominatim.openstreetmap.org/search.php?q=chugach+state+park&format=jsonv2
• Kachemak Bay state park: https://nominatim.openstreetmap.org/search.php?q=kachemak+bay+state+park&format=jsonv2
• Shuyak Island state park: https://nominatim.openstreetmap.org/search.php?q=Shuyak+Island+State+Park&format=jsonv2
• Denali state park: https://nominatim.openstreetmap.org/search.php?q=denali+state+park&format=jsonv2

That's probably still... a lot... of stuff; I wonder how much that'd blow the size up.

[biodranik]

Is the big overhead caused by "close to the north Mercator bound" coordinates?

[vng]

@person142 Cool!
Now could you please help to transform it to the list of 1-degree tiles? Like here:
https://github.com/organicmaps/organicmaps/blob/master/data/conf/isolines/countries-to-generate.json#L3368

There is a list of bottom-left (lat-lon) points of 1-degree SRTM tiles, that will be included in isolines generation. Having this list, I can run an isolines generator with say 50 meters step.

Defining (lat, lon) tile means that (lat, lon, lat + 1, lon + 1) bounding box will be with isolines.

Or write some Python script to fetch a list of tiles (with neighbors) from the list of POIs :)

[person142]

List of tiles here:

tiles.json

Code here:

https://gist.github.com/person142/f2e874ff8d08af4fdefffbe8fe71a0f7

so I can easily regenerate the list if something is amiss - I spot checked the tile locations, but easy to miss something.

[vng]

Great! Could you please make one unique tiles list, like:

"key": "US_Alaska",
        "value": {
            "profileName": "normal",
            "tileCoordsSubset": [
...

[person142]

This should do the trick:

tiles.json

[vng]

So, normal profile (50m) for these tiles will add approx 150Mb.

[pastk]

So same size as adding 100m for the whole Alaska.

[person142]

Interesting; I've seen the discussions #6157 and #4163 about isoline density - Alaska is definitely one of those steep places where denser isolines are nice, so going less than 50m might be a bummer (and going to 10m when the improvements ^ happen would be awesome).

i.e. if the 150Mb increase is acceptable I'd probably rather have the 50m lines on a smaller area than less-dense lines on a larger area.

[vng]

[person142]

Awesome! Got curious and compared:

Looks like that’s 100m - how much did it end up adding?

[vng]

Actually, 50 meters, they are visible from 200m zoom.
As I estimated before plus 150M. Now Alaska is 300M.

[pastk]

Please make a PR to merge all isolines profiles changes into the master.

[person142]

I've had an injury and hadn't been able to enjoy the new isolines yet, but now I've had a chance to try out some route planning with them, and they're awesome! Thank you for adding.