[mkgmap-dev] bearing/heading influence on routing

Wed Oct 23 21:47:57 BST 2013

Hi Gerd

>first see
>http://www.mkgmap.org.uk/pipermail/mkgmap-dev/2012q1/014145.html
>
>I see two different interpretations:
>1) mkgmap encodes the initial heading (A-B) and the final heading
>(C-D), always using one byte "curve data "
>for the final heading.
>2) display tool displays the initial heading as "direction", and one or
>two bytes curve data
>
>My theory is that the two byte curve data is used when we have a road
>where initial heading AND final heading are (very) different from the
>direction (A-D).
>Question is: what value is stored in the different fields?
>
>Does anybody already know more details?

Not me :)

>If not, what is the best way to find out?

Even though I only ever worked with a map consisting of 3 roads I
found it very difficult to keep track of all the data.

For the global index I eventually decided that a program that checked
theories about how the format worked rather than just displaying the
data was very useful.

So I would calculate the actual angles and distances for a road
segment and compare with the route data. Only print things that
don't fit with what is known. Concentrate on one test at a time.

I'd be interested in helping out it if possible.

A visual program to see large scale layout would
probably be useful too, but that is a lot of work. I might try
writing as an OSM file or SVG.

>I could either try to write a program that displays the data in real
>maps, or I could simply
>use try and error in the mkgmap write routine to find out how MapSource
>reacts one
>different codings. I played a little bit with the latter and I see
>differences in the calculated
>times.

Of course that is all interesting information too.

..Steve