Title: TMG angle offset
Post by: Holton181 on August 20, 2017, 07:49:25 PM
Post by: Holton181 on August 20, 2017, 07:49:25 PM
I noticed that the TMG line always has an angle offset. To me it appears like this offset is the TC + declination, but it's only my guess.
I have taken a screen dump of OM with heading and TC on the dashboard (don't bother about the compass values), a pic of that road section and a screen dump from another application (FlyIsFun, other road section) with a correct TMG for comparison it's not my device causing the offset somehow.
BR
/H
Title: Re: TMG angle offset
Post by: orux on August 21, 2017, 07:51:39 PM
Post by: orux on August 21, 2017, 07:51:39 PM
Hi,Quote from: "Holton181"
I noticed that the TMG line always has an angle offset. To me it appears like this offset is the TC + declination, but it's only my guess.
I have taken a screen dump of OM with heading and TC on the dashboard (don't bother about the compass values), a pic of that road section and a screen dump from another application (FlyIsFun, other road section) with a correct TMG for comparison it's not my device causing the offset somehow.
BR
Hello!
I think it is a problem with the map. Could you share it, or the map projection/datum?
Have you tested the app with an online map?
orux
Title: Re: TMG angle offset
Post by: Holton181 on August 21, 2017, 08:05:33 PM
Post by: Holton181 on August 21, 2017, 08:05:33 PM
Based on official and free Swedish map information from the Lantmäteriet, the Swedish mapping agency. Its not I who put them together tough.
The particular map I was using at this time was the "Topografiska kartan", but I have experienced this issue with several different maps, most likely with online maps too. But I will try it with an online map again next time I'm on the road again.
But I actually have had this issue for a long time, but remembered to take the screen dumps yesterday when my wife was driving and we passed some long, straight road sections.
Title: Re: TMG angle offset
Post by: orux on August 21, 2017, 10:23:12 PM
Post by: orux on August 21, 2017, 10:23:12 PM
Here is the maps:Quote from: "Holton181"http://www.bengt.nolang.se/kartor/
Based on official and free Swedish map information from the Lantmäteriet, the Swedish mapping agency. Its not I who put then together tough.
The particular map I was using at this time was the "Topografiska kartan", but I have experienced this issue with several different maps, most likely with online maps too. But I will try it with an online map again next time I'm on the road again.
But I actually have had this issue for a long time, but remembered to take the screen dumps yesterday when my wife was driving and we passed some long, straight road sections.
Thanks;
It should work fine in online mercator maps.
That map is a transverse mercator map. And it is very large. Because of that, lines of constant bearing (rhumb lines) are not parallel.
I have to find a solution for that kind of maps.
orux
Title: Re: TMG angle offset
Post by: Holton181 on August 21, 2017, 10:35:33 PM
Post by: Holton181 on August 21, 2017, 10:35:33 PM
Actually I do know the difference between mercator and transverse mercator maps, but not so much how it affects the TMG. No need to explain though, I trust you completely on this subject.
Do you have an online mercator map covering northern Sweden to recommend for testing?
(not the best kind of projection for this part of the world)
Title: Re: RE: Re: TMG angle offset
Post by: Holton181 on August 24, 2017, 02:04:01 PM
Post by: Holton181 on August 24, 2017, 02:04:01 PM
...
It should work fine in online mercator maps.
...
Indeed it does. Tested with openstreetmap cyclemap, attached screen dump (sitting on a train).
Good to know, hope you can find a fix for other projections though.
BR
/H
Title: Re: RE: Re: TMG angle offset
Post by: orux on August 24, 2017, 05:00:09 PM
Post by: orux on August 24, 2017, 05:00:09 PM
...
It should work fine in online mercator maps.
...
Indeed it does. Tested with openstreetmap cyclemap, attached screen dump (sitting on a train).
Good to know, hope you can find a fix for other projections though.
BR
/H
Hello;
could you try laste beta version?
if you go to maps-->map tweaks-->map mode, and then select 'north up' you should see that the map (the large one) rotates if you move it from East to West.
try then the TMG line.
orux
Title: Re: TMG angle offset
Post by: Holton181 on August 24, 2017, 06:23:44 PM
Post by: Holton181 on August 24, 2017, 06:23:44 PM
But unfortunately I will be on a hiking trip in the mountains untill Saturday 2:nd. I will try it out if a good opportunity comes ahead, but not many long, straight trails to use as a reference I'm afraid.
I get back when I have something to report.
BR
/H
Title: Re: TMG angle offset
Post by: Holton181 on September 09, 2017, 12:52:29 PM
Post by: Holton181 on September 09, 2017, 12:52:29 PM
With map mode 'Normal' the TMG seams to be correct in 7.1.3betta1.
But with 'Map North up' both the TMG and map itself start to jump back and forth a few degrees, independent of each-other. Very distracting, no confidence about correctness of TMG and actual map north.
What direction up is used when map mode is 'Normal'?
If you find a robust solution to TMG on transverse mercator maps (and other), how correct will the bearing and distance measurement be (when scrolling the map while GPS tracking on)? Are they even affected by map projection?