Notices

I installed the magnificient MM on my N800 and decided to collect map data from Europe, by zooming and moving around, all the while MM updated map data through my home WiFi, brilliant!

After playing a while with the app, I got a write error to the 4 GB SDHC - the external card seemed empty in Filemanager. I had some trouble with the card earlier, so thought it is some problem with the "experimental" SDHC or the card itself.

Took another card, a 2 GB regular SD. Was all over virtual Europe for a couple of hours... collected some 10's of MB's map data. Took the card to my PC, backed up the files and reformatted the card with FAT, to dedicate it to map data for the time being. Copied map files back to the card, ve-ery slow but eventually done.

Went back to N800 and MM, and continued getting zoom levels and areas. Stopped to check I'm not running out of capacity - no problem there. Again, back to MM and further surfing around the map, while talking on the phone with a friend. I used the Virtual Earth street maps repository.

Then, I got a write error again, ext. card in Filemanager is 0 kB cap, 0 kB used, 0 kB everything. Restarted the N800, ext. card does not appear to be inserted. Reinserted, to no avail. Took the card to the PC and it's Windows Explorer started acting like it sometimes does with damaged CD's - not responding, but not quite freezing either. Finally it tells me there's an I/O error with the card. Format is no-go, tried several card readers and OS's.

So, my other card is trashed too. Now I am afraid to start over with another, this time a 1 GB card, or to buy another 2 GB SD / 4 GB SDHC, and use them in connection with MM...

What might be the cause of the mishaps? Maybe the N800 external drive got pissed off with my attempting to format the non-functional 4 GB SDHC, and it thus destroyed the next best card?

Now seriously; Maybe the external drive is going bad? Maybe MM 1.4 with it's gazillion small files simply overstrained the controller and it flushed the FAT or something?

Does anyone have similar experiences? What could be done, except wait for John's version 2.0 of MM with dbase instead of numerous files?

Is it safe to continue collecting map tiles to other cards that I may get?

Later: I decided to try the 1 BG card - for a while everything went ok, then I got the same error, writing a file failed. Now, the card still contains the files but Filemanager tells me 0 kB available -- is it possible that FAT has run out of entries or what?

Well, I bought a new 4 GB Sandisk, but dare not use it for MM maps - what a drag! I have to wait for the 2.0 version it seems.

I did buy the Navicore package though so I can use the N800 for navigation, but Navicore really sucks a bit. No possibility to save routes, only POI's. It is therefore not very practical for longer journeys, in addition to it's inability to search for destinations on other maps than the presently used - so I cannot plan a trip through Europe but have to change the map for Germany, France, Benelux, Scandinavia.

I'm really looking forward to the MM 2.0 or else, maybe I will keep my "old" navigator, the Navigon 7000T which has better integration and can save routes, use a map of whole of Europe at once...

I'll reply my own post, at least a little: it seems that the maps files, 89 MB of them, take up 431 MB space on disk... interesting. After deleting some 500 MB of mp3's from the a.m. 1 GB card I can download map data again. The problem seems to be, if I want to get larger areas cached, I must a) take only a few zoom levels b) delete some areas every now and then c) get a card that can hold all the maps I need, bloated to 5 times their actual size by stupid Windows FAT arrangement.

Well, should I reformat the card in N800 and use 512 bits allocation size or what? My WinXP only offers default allocation size for FAT/FAT32.

Just wait a little (?) bit for MaemoMapper 2.0 : maps will be hold by a database : no loose space !

Fred

I would recommend reformatting with fat32 with 512 allocation size. The default is 4 KB, I believe, which results in a lot of space wasted due to slack space:

http://www.wikistc.org/wiki/Slack_space_data

Rocketman: That link is misleading as it discusses FAT12/FAT16 but not FAT32. In fact the default FAT32 cluster size is 16KB for a 1GB SD card and 32KB for anything larger (up to the 8GB SDHC currently available).

Since FAT32 also has a limit of (approximately) 4 billion clusters, this places a restriction on minimum cluster size that affects larger cards. You can have 512 byte clusters only on volumes up to 2GB. The limit becomes 1KB on a 4GB volume, 2KB on an 8GB volume, and so on.

lite: You can't "run out of FAT entries" (allocated by the formatter) before the volume is physically full. I currently use two 8GB cards in my N800, one with default 32KB clusters containing mostly MP3s, the other with 2KB clusters dedicated to Maemo Mapper files - literally millions of them. I'm sorry that I can't offer an explanation for your write errors, or more generally, for why my installation works and yours doesn't.

I ran into this problem as well (about 500M filling up a 2GB card), and formatting the card for FAT32 fixed it for me.

Using a database container doesn't automatically mean no wasted space;-)
It still depends on the data organisation, the access methods, and other things.

For a memory-limited device as the 770, it could also make sense
to store the tiles in an optimized database AND have them zipped beforehand.

Ray

On which system? On most systems default FAT32 cluster size is 4KB no matter the size.

Are you sure about this? is this result of some practical test?

While I'm not sure anything below 4KB block is supported with FAT32 at all, pure math says limits should be different. 4GB fits inside 32bits even when you address it by individual bytes, here you are addressing by clusters so why you can't have 512 bytes sized cluster with 4gb card? That should give you 2^32(=4294967296)/2^9(=512)= 8388608 clusters which should definitely fit into 32 bits of FAT32 limit. So in theory you could have 2^(32+9) bytes big card for 512 cluster size. Or if inforamation here http://www.cknow.com/ckinfo/f/FAT-Fi...tionTable.html or here http://en.wikipedia.org/wiki/File_Allocation_Table is true (and it probably is) and only 28 bits are used is still should allow 2^(28+9=37)=128GB card to have such small cluster.

Anyway making the cluster size small will make FAT table quite big. Generally it may not be very good idea to choose size below 4KB on gigabyte sized cards. Check this
http://www.storagereview.com/guide20...partFAT32.html
4GB card with 1KB block would give you FAT table size of 16MB and 512 bytes cluster will take 32MB.
Since most devices are not caching writes and keep FAT table in RAM and update it on every write this could make such card very slow and even not working in devices like PalmOS handhelds or digital cameras (due to device RAM limit).

But maybe linux is clever enough and handle big FAT tables sensibly so in N800 this could work?

I'm happy with using the internal flash for maps, they don't take at all as much space as I feared. Internal flash is jffs2, so a) it avoids the vfat cluster problem, and b) it compresses, so it avoids any 'padding' problems and wasted space (the actual png and jpg obviously can't be compressed, but any other wasted space will be).

Ray is right. No data structure, especially flat ones (i.e. disk-based), are without some amount of overhead. In Maemo Mapper v2.0's case, the overhead is in storing the "keys" that are used to find and access a given image in what is otherwise a sparsely populated matrix. This overhead, however, is significantly less than that of the internal fragmentation of typically formatted memory cards.

The images will be stored in the database as they are retrieved (from Google Maps, Virtual Earth, etc.). This is usually in either PNG or JPG format, neither of which reacts at all to zip compression, because they themselves are already heavily compressed.