While James was locating that cool tool, I was taking a different
approach the results of which are in the attached Excel sheet.
I took the .poly file from the following URL, found the min and
max lat and lon and then plugged in the tile X/Y calculations from
the second URL and then multiplied the delta tile numbers together
to get the total tile count per zoom level.?? My results are
higher than the geofabrik tool, but only to the tile count, not
the anticipated space consumed.
29,829,949 Total Tiles?? Dropping zoom 19 leaves 7,465,346 which
is almost double what the Gofabrik tool shows.?? But if you read
their caveat, they only counted the tiles on their server.?? If a
particular map are has never been visited, they won't even have
that rendered tile to count.?? But if you download everything
within that bounding box, you'll get my numbers.
19 - 22,364,600
18?-? 5,595,993
17 - 1,400,377
16 -? ? 350,784
15 - 88,218
14 - 22,270
13 - 5,676
12 - 1,452
11 - 408
10 - 102
9 - 36
8 - 15
As James suggested, actually look
critically at the map at the various zoom levels and you'll likely
find that you really don't need much beyond 15 or 16 which, as you
can see above, drastically reduces the tile file count.
But I hope you begin to understand why
it's never a good idea to want to preload a large area of tiles.??
The load on the tile server is EXTREME in rendering all of those
tiles, most of which will NEVER be viewed.
Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and
Win32
On 2/21/2023 11:00 AM, James Ewen
wrote:
Let me answer my own question...
I just found a new toy!
You'll need 19 GB of file storage for all zoom levels down
to 18. I think you'll need another 48 GB of storage for zoom
level 19 if I can do math properly.
If you are using these offline maps for something like
ARHAB balloon recovery, or similar, you might find that the
extreme zoom level maps contain very little extra information
than the tiles a couple levels up. There are very few areas
where information on every blade of grass, and bit of gravel
are mapped.
The precision of the data in the OSM database is no where
good enough to have these extreme zoom levels provide much
useful information.
Maybe take some time to run through your process (whatever
it is you are trying to do offline), and have a look
specifically to see if the tightest zoom levels are actually
required.?
When I started playing with OSM I wanted similar offline
maps for the province of Alberta in Canada.
228 GB is a hefty chunk. I found that I really didn't need
anything?closer than zoom level 14.
Looking at your area, by the time you get to zoom level 15,
you already have house footprints, and just about all of the
information that can be seen. Zoom level 16 has bus stops, and
zoom level 17 puts addresses on houses. I'm not sure what more
information might be found on zoom 18 and 19. (I just found
some park benches and garbage cans at zoom level 19)
I guess there is an argument that can be made for needing
very tight zoom tiles, but generally very detailed work
doesn't happen on a large scale area all at once.?
>Województwo podkarpackie (Subcarpathian
Voivodeship) is only a 111 MB download for the original
OSM data.
>
>
Lynn, for illustrative purposes, could you estimate
the storage necessary to hold all of the rendered
tiles at all zoom levels for this same area?
I don't believe?that many people understand the
sheer size of all the rendered tiles.
James
VE6SRV
