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Optimising TAR-ed maps and atlases

 
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guest



Joined: 08 Oct 2006
Posts: 4793

PostPosted: Tue Jun 21, 2016 1:53 pm    Post subject: Optimising TAR-ed maps and atlases Reply with quote

Dear Kruch and TB users!

Forum and wiki teaches that for best performance TAR-ed maps should be packed in following order:
Quote:
first "*.map" file, then "*.set" file, and then "set" folder with tiles.


Of course, I agree with it, but often by default tiles from "set" folder are TAR-ed in random order (depends on software and settings used).
That's why it's better to "feed" TAR archiving software of ordered list of tiles from "set" folder.
I know from forum that "*.tmi" and "*.tmc" files do their job for packed maps, but for basic/oldstyle phones any improvement is helpful.
I also know from my IT experience, that ordered TAR files with huge amounts of small files (exactly like TB maps) have also smaller final size, what is additional advance!

So my questions are:

1. What is the order of tiles reading by TB?
Is it from left to right (W/E), then one row lower (N/S) and again left to right (W/E)?
Quote:
tile_0WE_0NS.png, tile_1WE_0NS, tile_2WE_0NS.png, ..., tile_0WE_1NS.png, tile_1WE_1NS.png, tile_2WE_1NS.png, ...

Or in opposite way?
Quote:
tile_0WE_0NS.png, tile_0WE_1NS, tile_0WE_2NS.png, ..., tile_1WE_0NS.png, tile_1WE_1NS.png, tile_1WE_2NS.png, ...

If it's not so important as I think, which may be better/suggested?

2. Are both "*.tmi" and "*.tmc" file needed? Or only one of them is enough? Which one is preffered by TB?

3. In TAR-ed atlas index file (like popular "cr.tar") there are obviously empty "set" folders (in maps folders in layers folders.)
Are they generally needed by TB in its empty state in atlas index file? Or it may be deleted without performance lost? Which way is preffered by TB?

Thank you in advance for actual answers.
If they are helpful I will finally publish them on the forum in form of automated script for easy use.

With best regards,
Bartek (PL)
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Ranger



Joined: 12 Dec 2006
Posts: 6022

PostPosted: Tue Jun 21, 2016 2:55 pm    Post subject: Reply with quote

Hi,
Compiled script for packing maps/atlases is already available on forum
http://www.trekbuddy.net/forum/viewtopic.php?t=790&postdays=0&postorder=asc&start=56
Seems effective. You can check order of files it creates in archives.
Map tiles support is just app internal think. It is enough for user to know which tools can be used to prepare maps/atlases.
Second question - only one of acceleration file is used at time, means tmi or tmc (tmc is just binary version of tmi, created by app itself).
Tmc is prefered one, but sometimes app just couldn't create it due ie write microSD restrictions, so tmi is used instead.
And last answer - today probably is better to use new headers in atlas, to control atlas type support in app too.


Last edited by Ranger on Tue Jun 21, 2016 8:50 pm; edited 1 time in total
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kruch
Site Admin


Joined: 02 Jul 2006
Posts: 5658

PostPosted: Tue Jun 21, 2016 4:32 pm    Post subject: Reply with quote

1. from left to right, top to bottom.

It is true that on some old and Symbian devices, performance penalty of going back in archive is significant, but ordered tiles set cannot help in situations when user just drags the map in the direction where goping back is inevitable anyway... Razz

2. TB first looks for tmc, then tmi, if tmc does not exist it will try to create it (may fail due to reasons mentioned by Ranger)

3. empty "set/" folders can be safely deleted I think (all empty folder entries in atlas index file are skipped when TB scans the tar archive)
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Freddie



Joined: 11 Jun 2008
Posts: 71

PostPosted: Thu Aug 11, 2016 7:26 am    Post subject: Reply with quote

Quote:
3. empty "set/" folders can be safely deleted I think (all empty folder entries in atlas index file are skipped when TB scans the tar archive)



atlas_tar.zip
 Description:
Delete empty folders "set" from the header in the new script. The header is a little smaller.

Download
 Filename:  atlas_tar.zip
 Filesize:  53.15 KB
 Downloaded:  139 Time(s)


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