The reason I want that is, almost all humans have a GPS device in their pocket. You could easily get your approximate location from this, even without cell service. Implementation could be a PWA.
The amount of map data for any reasonable area is going to be too large for a PWA, though it would technically be possible to do with existing map viewers and this format. (Eg maplibre or leaflet)
edit: Initially underestimated so did some calculations below
Key Data Points for Estimate of SVG Size
- Radius of Earth: 6371 km
- Surface Area of Earth: 510e6 km^2
- Approximate Number of Countries: 250
- Land Area of Earth: 29% of Surface Area = 150e6 km^2
- Average Land Area per Country: 150e6 km^2 / 250 = 6e5 km^2
- Country Closest to Average Size: Ukraine, with 603550 km^2, or roughly 6e5 km^2
- World Resources Institute Measure of Ukraine Coastline: 4953 km, or around 5e3 km
1. Only coastlines matter for the paths.
2. Resolution set at 10 meters.
- Coastline Points for Average Country:
- 5e3 km = 5e6 m
- Equals 5e5 X,Y points (at 10m resolution)
- Total Points for All Countries:
- 250 countries * 5e5 points = 1.25e8 X,Y points
- Storage Requirement for Each Point:
- 6 figures per coordinate + delimiters = roughly 15 bytes
- Total Storage = 1.25e8 points * 15 bytes = ~1.875e9 bytes or about 1.875 GB
What about 1000m resolution? 20 megabytes. Much more achievable.
There also must be more countries smaller than the average country than there are larger ones (https://www.worldometers.info/geography/largest-countries-in... confirms that. Ukraine is 45th of 223, or about 20% down.)
So, I guess yours is underestimating the size.
You probably get a better estimate by using the Ukraine to estimate the scaling constant (√603,550km²)÷4953km and then use a list of land areas to estimate border lengths.
116KB - 5MB for country borders
16MB - 52MB for ~50K city/county level borders based on geoBoundaries
The range of sizes depends on how much custom compression/simplification you put into it. The source files are about 10x bigger, but that's already pretty small.
Topojson might be even smaller though.
Check the repo for details /selfplug https://github.com/SmilyOrg/tinygpkg-data
Well, mostly that it's text / XML you usually have to parse in full and boundaries are data heavy, so if you have anything more than a world map, I don't see that working very well.
In contrast with the OP or GeoPackage, you can query by tiles/range and only extract the boundaries you need if you're zoomed in somewhere. If you use Tiny Well-Known Binary compression, you can also shrink the data quite a bit while keeping the querying capabilities.
But if you only ever need to render the whole thing, topojson is probably the winner as it cleverly encodes only unique borders once, so it tends to be a lot smaller.
And of course if SVG works for your case, go ahead and use it, it's surely the easiest way to render vector gfx in the browser :)
FWIW, I've got an official 900MB geojson of borders from a large unnamed multinational NGO type that's particular about their mapping.
At z=4, or 600m resolution, it's a 2.5MB pmtiles, at z=10 (10m resolution) it's 83M.
That's just the ADM0 borders, adding local borders would obviously increase the size.
1) Just use the overview tiles from the global protomaps dump (OSM source). The getting started guide can walk you through some of it: https://docs.protomaps.com/guide/getting-started but you'd want to use the pmtiles tool to extract the widest zooms from the global dataset.
pmtiles extract https://build.protomaps.com/20231023.pmtiles overview.pmtiles \
--maxzoom=4
2) If you have/find your own data, use Felt/tippecanoe to convert it.
tippecanoe -z4 -o overview.pmtiles data.geojsonI really appreciate you showing me how to do that. Thank you very much!