TrekBuddy

guest · Joined: 08 Oct 2006 Posts: 3949

Hello,

I'm a new and fan user of TB, with a SE W660i and last TB version. It's working very well, I will only use it for my next road/bike/paraglider trip !! Smile

I have a problem of map display shift (about 1.5km) with several maps (from an Atlas) I made with the web site gm2tb. With a big scale (10km/cm) of those maps, I have a shift, with a small scale (500m/cm), the position is correct...

Do you have an idea about this problem ?

thx a lot!!!

Romain

ps: I can not send here my gpx log of the trip, I'm not allowed to attach it ...

temptrekbuddy · Joined: 27 Nov 2006 Posts: 193 Location: Poland

kruch · Site Admin Joined: 02 Jul 2006 Posts: 5088

Isn't this a known issue that gm2tb calibration for big scale isn't accurate.... ?

ck3d · Joined: 08 Dec 2007 Posts: 2

In the middle of large scaled map-sets TrekBuddy has got latitude deviations.
The position is correct displayed at bottom or top of map-set.
I think there is a mapping problem in TrekBuddy!

I tested it with gmap and osm.

Ranger · Joined: 12 Dec 2006 Posts: 4726

First check your maps in OziE, for example using tracks.
I saw a lot of maps wrong calibrated.
If you have map working in OziE well and not working in TB, just attach sample or link to sample.
No way to check problem without maps you used.
Problem with gm2tb is well known, projection info is not included in calibration file, so only detailed zoom levels can work.
Up to this time no solution from tool author is available.

ck3d · Joined: 08 Dec 2007 Posts: 2

Ok, then I was wrong.
I tested it with following sites:
http://gm2tb.awokenmind.de/
and
http://osm.bandnet.org/browse/

I hope these sites can cure that problem!

kruch · Site Admin Joined: 02 Jul 2006 Posts: 5088

I'll try to compare two large scale Google maps of the same area - one created by gm2tb, and another by GoogleHackPureJava2 (if it still works against current Google maps).

kruch · Site Admin Joined: 02 Jul 2006 Posts: 5088

OK... I could not get Google maps, but got VirtualEarth maps. I'm convinced there is a bug in gm2tb.
On attached pictures, you may see that location of small town Beroun south-west of Prague. (approx lat 49deg 57min lon 14deg 4min)
Coordinates from alternative downloader and online map service (mapy.cz) matches, but the same location is shifted by many kilometeres on gm2tb map.

Since gm2tb maps does not start/end on Google map tiles boundaries (unlike map from GoogleHackPure java and its successor), I suspect there a bug in calibration in gm2tb, where some calculation is therefore needed to get map corner points that do not match map tiles corner points. In fact, gm2tb does not have to do this recalculation, since Points in the Ozi calibration file do not have to be at the map corners...

olegich · Joined: 07 Aug 2007 Posts: 70

kruch
It appears on maps with more than 7 vertical tiles(256x256).
More tiles-more shift (scales are equal).

Also with the same dimension and the same scale but different vertical borders.
pic#1: 61.270N 57.704N (small shift, crossroad at top of the map)
pic#3: 63.234N 59.889N (shift has grown)

TB_____________________OZI

added: i have to say that 7 tiles for maps with zoom=10 (in google notation), that i've attached and in high latitudes (due to mercator projection)

start78 · Joined: 17 Oct 2007 Posts: 186

Hi kruch,

since you already made the first steps to solve this issue, wouldn't you think it a good idea to contact the gm2tb-creator and help him solve it?

I made an attempt to find out what is wrong here. Until now i only know that he created gm2tb by reverse engineering from mapexplore. (I was in e-mail contact with him. His mail adress is easy to find in his awokenmind-blog)

According to his statistics there are many people using gm2tb. Perhaps joining forces with him can be usefull for both sides?

My first idea (perhaps you remember) was a manual calibration in tb. I think the upper left corner of a large map should be correctly calibrated. Perhaps if you specify just one more point on the map inside tb it could calculate the misscalibration and correct it. This would be a poor workaround since it doesn't solve the original problem and blotes the program...

<edit>

Ranger · Joined: 12 Dec 2006 Posts: 4726

Hi start78,
First of all, I use working well Mercator projected maps in TB.
Map calibration is not just playing with numbers, without understanding what they represents. Bug in tool is known, so Kruch have nothing to do with it in TB. I can say again - before you use GM map in TB, try to check how it works in OziE. Doesn't work. From TB point of view all is clear - if datum/projection info is not included in calibration file, TB defaults to WGS/UTM. Question is what kind of coordinates gm2tb will write to calibration file.
Regards,
Ranger

start78 · Joined: 17 Oct 2007 Posts: 186

I don't know much about calibration and projection. And i think the creator of gm2tb doesn't, too. But you and kruch seem to know.

That's why i'm asking all the time. If you can explain me what is necessary or tell me where i can easily get this knowledge, maybe i can figure out what to do and tell the gm2tb-creator about it.

Is it so hard to calculate the needed projections if you have a calibration point and a zoom level in gmaps?

Gm2tb is already one of the top results if you do a google-search about trekbuddy and many people seem to use it (over 600 maps per day) because you can create a ready-to-use tar-map without any knowledge about map-creation or any program installed on yout PC. I don't know how to make such a tool but i would really like to help fixing this annoying bug so the community (and me, of course) has a handy tool for creating tb-maps in no-time.

I know a forum isn't about asking stupid question that could have been answered by doing a google-search...

Ranger · Joined: 12 Dec 2006 Posts: 4726

Hi again,
Technical knowledge about maps is one, but you touch few other thinks.
TB is mainly designed for outdoor. For such activities you need suitable maps.
First, I don't see too much value of GM road maps in outdoor activities. But probably you are right, street and road maps can be interesting for GPS beginners to start, if they couldn't find better map sources.
Remember, Google Terms restricts use of their maps with other navigation software.
Second, as an example, last year we started (in my country) cooperation with commercial topo maps producer to have TB ready maps suitable for outdoor activities. And we have first bundle of TB with electronic & paper maps available now Smile

More info about it you can find in TB wiki.
Which way to choose ?
Regards,
Ranger

start78 · Joined: 17 Oct 2007 Posts: 186

The coop with compass is a good idea. But it costs money and isn't available everywhere.

About using gmaps for outdoor use: yes, they lack topo infos but at least for my region they are extremely detailed concerning ways and paths.

As long as the gm2tb-maps are for free and TB is for free i don't see many conflicts with Google Terms.

Why should treckbuddy be reduced to outdoor navigation? I already made very good experiences supporting navigation per paper roadmaps (ask my girlfriend).

This goes Off-Topic...

Ranger · Joined: 12 Dec 2006 Posts: 4726