<html>
<head>
<style><!--
.hmmessage P
{
margin:0px;
padding:0px
}
body.hmmessage
{
font-size: 12pt;
font-family:Calibri
}
--></style></head>
<body class='hmmessage'><div dir='ltr'>Hi Marko,<br><br>thanks, I think the 2nd block in the comments for the code suggest something else:<br> // detect the "shallow turn" scenario where at a junction<br> // on some "main" road, the side road leaves the main<br> // road at a very shallow angle and the GPS says "keep<br> // right/left" when it would be better if it said "turn<br> // right/left"<br><br> // also helps to produce a turn instruction when the main<br> // road bends sharply but the side road keeps close to the<br> // original heading<br><br>Your example matches the "shallow turn" scenario, I think my example <br>matches the 2nd one. <br><br>I do not yet understand the effect of the parameter (1/2/3) for the option, I guess<br>I have to trace some more examples...<br><br>Gerd<br><br><br><div>> Date: Fri, 7 Aug 2015 12:22:25 +0300<br>> From: marko.makela@iki.fi<br>> To: mkgmap-dev@lists.mkgmap.org.uk<br>> Subject: Re: [mkgmap-dev] What is the idea behind --adjust-turn-headings?<br>> <br>> On Thu, Aug 06, 2015 at 03:11:23PM +0200, Gerd Petermann wrote:<br>> >I understand that this option should help to produce good driving <br>> >instructions. Anyhow, I wonder if the result is really better.<br>> ><br>> >The two screenshots show the difference at this node:<br>> >http://www.openstreetmap.org/node/21725099<br>> <br>> This node is a 3-way T-shaped crossing, with roughly 90° angles between <br>> the 3 roads.<br>> <br>> If my memory serves me correctly, the motivation behind <br>> --adjust-turn-headings was to help in cases where you are entering a <br>> Y-shaped crossing from the bottom, and there is a very sharp angle <br>> between the branches of the Y. At the extreme, one of the branches is <br>> going straight, and the other is at some very small angle. In this case, <br>> you might want a direction such as "turn left" or "turn right", if <br>> Garmin cannot produce a "keep left" or "keep right" direction.<br>> <br>> IIRC, without the option, when entering this cycleway ramp from the <br>> north:<br>> <br>> http://www.openstreetmap.org/node/33986539<br>> <br>> the Garmin Edge 705 would not give any announcement that I have to turn. <br>> With --adjust-turn-headings, it would tell me to turn left. I do not <br>> have the device any more, so I cannot test this.<br>> <br>> >Before I can fix the additinal problems introduced by the naming of <br>> >service roads I'd like to understand if this is the intended behaviour.<br>> <br>> I would say that it is not. If you have a T-crossing with the nodes AC <br>> at the end of the horizontal section of the T and the node B at the <br>> bottom, and you are going left to right from A to C, the road names or <br>> the way how the roads are split to way segments should not matter. It <br>> also should not matter if the route A-C is bending slightly.<br>> <br>> IMO, what should matter is the difference of the angles of the roads. <br>> In this case, the angle difference between A-C and A-B is about 90°. If <br>> that angle difference were smaller than some threshold (say, 45° or <br>> maybe even 30°), then it would make sense to adjust the turn headings. <br>> Otherwise the turn directions would be simply noise.<br>> <br>> Marko<br>> _______________________________________________<br>> mkgmap-dev mailing list<br>> mkgmap-dev@lists.mkgmap.org.uk<br>> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev<br></div> </div></body>
</html>