maemo.org - Talk - Plans for Maemo Mapper v2.0

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- Applications (https://talk.maemo.org/forumdisplay.php?f=41)

- - Plans for Maemo Mapper v2.0 (https://talk.maemo.org/showthread.php?t=6425)

rhouge

2007-05-22 18:31

Re: Plans for Maemo Mapper v2.0

Quote:

Originally Posted by gnuite (Post 49368)

I'd have to investigate further, but I'm pretty sure that this sort of thing would be more or lerss impossible for a user-level (i.e. not root) program to accomplish. It's too bad, too, because flite's volume can be so low at times, and it's already hard enough to understand without music playing at the same time.

Bummer. How about the other half of that equation, regarding bringing mapper up to the foreground?

ioan	2007-05-22 19:54

Re: Plans for Maemo Mapper v2.0

Here is an idea.
Make in the db where you want to keep the map tiles two tables.
one coordinates and CRC of the image tile and in the second table the CRC of the image and the image. This way you can exclude duplicates, we'll have only one tile that is blue... or white... or whatever.

you make the CRC as a unique key in the images table.
when you insert, you insert in both tables, in the image table the insert will fail (if the CRC is already there). this way you won't have to check if the image is already in the table before inserting.

What do you think?

-ioan

gnuite

2007-05-22 23:05

Re: Plans for Maemo Mapper v2.0

Quote:

Originally Posted by ioan (Post 49436)

Here is an idea.
Make in the db where you want to keep the map tiles two tables.
one coordinates and CRC of the image tile and in the second table the CRC of the image and the image. This way you can exclude duplicates, we'll have only one tile that is blue... or white... or whatever.

you make the CRC as a unique key in the images table.
when you insert, you insert in both tables, in the image table the insert will fail (if the CRC is already there). this way you won't have to check if the image is already in the table before inserting.

What do you think?

Sounds like a good idea, although I'll probably reserve it for tiles that are 103 bytes large, since those are the only ones that are a solid color. All that CRC calculation would be such a waste of CPU.

jaska k

2007-05-24 11:15

Re: Plans for Maemo Mapper v2.0

Maemo Mapperi is great because as far as I know it is currenlty the only available native WMS-client for maemo platform. And WMS allows me to serve my own maps quite easily. Plans for db-utilization sound great, expect that features of PostGIS are perhaps too far from here.

WFS-support for MM would be nice :rolleyes:

insert_nick

2007-05-24 11:44

Re: Plans for Maemo Mapper v2.0

Quote:

Originally Posted by ioan (Post 49436)

Here is an idea.
Make in the db where you want to keep the map tiles two tables.
one coordinates and CRC of the image tile and in the second table the CRC of the image and the image.

+1 to this.

Or, if there's some fast way to detect if an image is just a single color one while retrieving it, avoid storing it in the database and store just the corresponding color information. So, imagine a table with fields:

coordinates | display

"display" is a short string: when it does begin with "#", the value is considered as a color (to render a monocolor tile for that coordinates), otherwise it is considered as the id of the image to render (picking it from a second table with fields: id | image).

ioan	2007-05-24 16:52

Re: Plans for Maemo Mapper v2.0

I did a test with creating a table just for the tile image and the crc32, the table looks like this:

CREATE TABLE testtable ([crc32] VARCHAR (8) PRIMARY KEY UNIQUE, [maptile] BLOB COLLATE NOCASE);

I didn't do anything for coordinates, nothing special to see there.

I ran the test on 213304 map tiles, and at the end, in the database I had 135417 unique tiles (77887 were duplicates!).

The 213304 tiles on my computer use 897MB (size on disk), and the database, after excluding the duplicates is about 290 MB.

I used sqlite3.

-ioan

gnuite

2007-05-24 19:20

Re: Plans for Maemo Mapper v2.0

Quote:

Originally Posted by ioan (Post 49626)

I ran the test on 213304 map tiles, and at the end, in the database I had 135417 unique tiles (77887 were duplicates!).

How many of those duplicates (if any) are greater than 103 bytes?

ioan	2007-05-24 20:21

Re: Plans for Maemo Mapper v2.0

Quote:

Originally Posted by gnuite (Post 49646)

How many of those duplicates (if any) are greater than 103 bytes?

I didn't count them... but just now I modified my test app to check that too.. and after a little over 9000 files, I have this:

http://ioanghip.googlepages.com/crc.jpg

the caption shows the number of processed files, the list, first field is the size, the second how many duplicates with that size...

I suppose on windows we have 106 bytes not 103.

-ioan

Ferd	2007-05-24 23:40

Re: Plans for Maemo Mapper v2.0

Any plans for adding a Golf Course GPS program that would allow for course maps to be built, shared or downloaded from a respository? Possibly a program similar to Sky Caddie. This would be a superb mapping application.
I really appreciate your present Maemo Mapper program and look forward to version 2.0

jpj	2007-05-25 00:50

Re: Plans for Maemo Mapper v2.0

Quote:

Originally Posted by ioan (Post 49649)

I suppose on windows we have 106 bytes not 103.

Depends on the repository. Also on Windows, I see the following sizes for featureless (duplicate) tiles from the various standard Maemo Mapper map sources:

Google Streets: 103 bytes
Virtual Earth Streets: 106 bytes
Virtual Earth Satellite or Hybrid: 1652 bytes

Among my Google Satellite downloads, I have a lot of duplicate 1755 byte files, which in fact are NOT maps, even though they commonly appear clustered in featureless ocean areas. (Some of the true satellite map files are actually smaller.) Opening these files as text reveals the following HTML error page, saved under the target JPG filename:

Code:

<html>

<head>

<title>403 Forbidden</title>

<style>

body {

font-family: Arial, sans-serif;

}

</style>

</head>

<body bgcolor="#ffffff" text="#000000" link="#0000cc" vlink="#551a8b" alink="#ff0000">

<table cellpadding="0" cellspacing="0" border="0">

<tr>

<td><b><font face=times color=#0039b6 size=10>G</font><font face=times color=#c41200 size=10>o</font><font face=times color=#f3c518 size=10>o</font><font face=times color=#0039b6 size=10>g</font><font face=times color=#30a72f size=10>l</font><font face=times color=#c41200 size=10>e</font></b></td>

<td valign=middle width="100%" style="padding-left: 10px">

<table bgcolor="#e5ecf9" width="100%" cellpadding="0"

cellspacing="0" border="0" style="border-top: 1px solid #3366cc">

<tr>

<td><font size="+1">&nbsp;<b>Error</b></font></td>

<td align="right" nowrap><font size="-1">&nbsp;</font></td>

</tr>

</table>

</td>

</tr>

</table>

<blockquote>

<h1>We're sorry...</h1>

<p>... but your query looks similar

to automated requests from a computer virus or spyware

application.  To protect our users, we can't process your request

right now.

</p>

<p>We'll restore your access as quickly as possible, so try again soon. In the meantime, if you suspect that your computer or network has been infected,

you might want to run a <a href="http://www.download.com/Antivirus/3150-2239-0.html"> virus checker</a> or <a href="http://www.download.com/sort/3150-8022-0-1-4.html">spyware remover</a> to make sure that your systems are free of viruses and other spurious software.

</p>

<p>We apologize for the inconvenience, and hope we'll see you again on Google.











</blockquote>

<br><table width=100% cellpadding=0 cellspacing=0>

<tr><td bgcolor=#3366cc><img alt="" width=1 height=3></td></tr>

</table>

</body>

</html>

"Silly wabbit, looking for closeups of the ocean. Must be a bot." ;-)

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