Notices

i noticed the rather large storage area needed for mappero maps. I downloaded about 900MB of maps, but it took 15GB of storage on n900... And i only downloaded the maps for the only a few states in north east of USA. This means that the storage on n900 can't even handle the entire USA -- it will run out of space really quick.

This is completely unacceptable to waste so much space.

its 1 map per zoom level you can change what zoom levels your downloading.

that is not the point. the point is the maps being downloaded is only 900MB, but it took 15GB space on disk.

Compression is a wonderful (and not terribly new) thing.

Stating that the device's storage "cant even handle the entire usa" is totally arbitrary, as like Cobra has said, there are separate downloads for each zoom level.
At minimum zoom, you can get the entire usa on like 5 map tiles, which is a few KB of download. At max zoom however, the USA is probably tens of millions of tiles. Between these, there are 19 other levels of zoom, each having their own sets of map tiles.
Choose your zoom levels carefully, and you can happily get large areas covered at low and high zooms with comparatively little space usage.

I take it, then, you'll be letting the community, particularly all the guys working so hard on the various tile-based GPS mapping programs, when you're ready to release your vector-map-based GPS suite?

I don't use Mappero so I'm not familiar. If they are many small files then it's probably cluster slack waste.

you guys are not getting the point... the point is the size of the maps are small, 900MB total. but they took 15GB on the n900, probably due to they are small files.

so where does mappero store the maps? i'd like to be able to manually clear the cache when i uninstall the app..

Looks like Mappero is using the same maps tile cache that other maps programs on N900 use, in /home/user/MyDocs/.maps/

And indeed it seems to be many small files. For example I just did a small quick test. My data in MyDocs/.maps/ total about 5 megabytes file size, but is using 28 megabytes on disk because of the slack space.

It's a decades-old problem. On FAT file system (and others) all files use a multiple of the block size. So if you have 4096-byte blocks, a 1-byte file will use 4096 bytes on disk, and a 4000-byte file will use the same amount. A 4097-byte file will use 8192 bytes. Etc.

The only way to avoid it that I can think of are either to change the on-disk format to use container files of some kind (this is not a simple solution & would require map software authors to completely change their programs). Otherwise maybe you can create a loopback device and format it with a filesystem that either uses a smaller block size or supports tail packing, and use that for the tile cache.

For more info see Wikipedia article about Block Suballocation:
https://secure.wikimedia.org/wikiped..._suballocation

I suspect the large storage requirements have a lot to do with the FAT32 filesystem used for MyDocs. The block size is 64k so each file will take 64k no matter if it is 2k or 40k.

The solution would be to either use NTFS or another storage layer on top of the filesystem like sqlite - with the drawback that you'd need to use tools to manage the cache and is less interoperable with other applications (for example, I understand cloudGPS can use the mappero tile cache).

but the FAT32 argument may not be so valid with a file that is larger than 64k, would it? i would imagine the maximum wasted space would be 65535 bytes assuming you filled up the previous blocks and 1 byte overflowed into the next block. ????