![Wed Mar 26 14:17:21 2014 (69.8k) by lixus [...] muellers.ms](/Ticket/Attachment/1343533/712989/paris.jpg){kind=link}
| CC: | Jim [...] Gibson.org |
| Subject: | lon off by 360° if $geo->at( @origin, $range, $bearing ); crossing prime meridian |
| Date: | Wed, 26 Mar 2014 19:17:01 +0100 |
| To: | bug-geo-ellipsoid [...] rt.cpan.org |
| From: | Lixus Zoran <lixus [...] muellers.ms> |
Hello,
I would like to draw circles around locations,
e.g. a 300km circle around paris and store it as gpx track.
This works fine using $geo->at(...) but it returns strange lon values
if crossing prime meridian, so i added the fix in line 22 (commented out in this example)
which works for me but i do not understand why.
1 use Geo::Ellipsoid;
2
3 $geo = Geo::Ellipsoid->new(
4 ellipsoid=>'WGS84',
5 units=>'degrees',
6 distance_units => 'kilometer',
7 );
8
9 my @origin = ( 48.849954, 2.333179 ); # paris
10 my $range = 300;
11
12 print<<EOF;
13 <?xml version="1.0"?>
14 <gpx version="1.0" creator="Geo::Ellipsoid" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.topografix.com/GPX/1/0" xsi:schemaLocation="http://www.topografix.com/GPX/1/0 http://www.topografix.com/GPX/1/0/gpx.xsd">
15 <trk>
16 <name>Track</name>
17 <trkseg>
18 EOF
19
20 for($bearing=0; $bearing<=360; $bearing +=10 ) {
21 my ($lat,$lon) = $geo->at( @origin, $range, $bearing );
22 #$lon = $lon - 360 if $lon > 180;
23 printf("\t\t<trkpt lat=\"%s\" lon=\"%s\"></trkpt>\n", $lat, $lon);
24 }
25
26 print<<EOF;
27 </trkseg>
28 </trk>
29 </gpx>
30 EOF
This returns these values, but as you can see in line 28 the output has lon="359.809374330679"
this can be fixed with "$lon = $lon - 360 if $lon > 180;" I would like to understand why
and 180 was just a guess.
1 <?xml version="1.0"?>
2 <gpx version="1.0" creator="Geo::Ellipsoid" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.topografix.com/GPX/1/0" xsi:schemaLocation="http://www.topografix.com/GPX/1/0 http://www.topografix.com/GPX/1/0/gpx.xsd">
3 <trk>
4 <name>Track</name>
5 <trkseg>
6 <trkpt lat="51.546998949586" lon="2.333179"></trkpt>
7 <trkpt lat="51.5036953778651" lon="3.08318739911697"></trkpt>
8 <trkpt lat="51.3753396739588" lon="3.80639279801629"></trkpt>
9 <trkpt lat="51.1665130456171" lon="4.47739812085026"></trkpt>
10 <trkpt lat="50.8845809546462" lon="5.07346914659855"></trkpt>
11 <trkpt lat="50.539319549186" lon="5.57552362983861"></trkpt>
12 <trkpt lat="50.1424483024434" lon="5.96878457958342"></trkpt>
13 <trkpt lat="49.7071107601912" lon="6.24308617339316"></trkpt>
14 <trkpt lat="49.2473425643629" lon="6.39286886592435"></trkpt>
15 <trkpt lat="48.7775584101813" lon="6.41693111348806"></trkpt>
16 <trkpt lat="48.3120799353" lon="6.31801680015862"></trkpt>
17 <trkpt lat="47.864717061353" lon="6.10231330110236"></trkpt>
18 <trkpt lat="47.4484075391441" lon="5.77892110945565"></trkpt>
19 <trkpt lat="47.0749140294542" lon="5.35933804187563"></trkpt>
20 <trkpt lat="46.7545749304819" lon="4.85698366932089"></trkpt>
21 <trkpt lat="46.4961038896551" lon="4.28677529920804"></trkpt>
22 <trkpt lat="46.3064329258887" lon="3.66475641413431"></trkpt>
23 <trkpt lat="46.1905947940517" lon="3.00777171107457"></trkpt>
24 <trkpt lat="46.1516412330701" lon="2.333179"></trkpt>
25 <trkpt lat="46.1905947940517" lon="1.65858628892543"></trkpt>
26 <trkpt lat="46.3064329258887" lon="1.00160158586569"></trkpt>
27 <trkpt lat="46.4961038896551" lon="0.379582700791956"></trkpt>
28 <trkpt lat="46.7545749304819" lon="359.809374330679"></trkpt>
29 <trkpt lat="47.0749140294542" lon="359.307019958124"></trkpt>
30 <trkpt lat="47.4484075391441" lon="358.887436890544"></trkpt>
31 <trkpt lat="47.864717061353" lon="358.564044698898"></trkpt>
32 <trkpt lat="48.3120799353" lon="358.348341199841"></trkpt>
33 <trkpt lat="48.7775584101813" lon="358.249426886512"></trkpt>
34 <trkpt lat="49.2473425643629" lon="358.273489134076"></trkpt>
35 <trkpt lat="49.7071107601912" lon="358.423271826607"></trkpt>
36 <trkpt lat="50.1424483024434" lon="358.697573420417"></trkpt>
37 <trkpt lat="50.539319549186" lon="359.090834370161"></trkpt>
38 <trkpt lat="50.8845809546462" lon="359.592888853401"></trkpt>
39 <trkpt lat="51.1665130456171" lon="0.188959879149733"></trkpt>
40 <trkpt lat="51.3753396739588" lon="0.859965201983715"></trkpt>
41 <trkpt lat="51.5036953778651" lon="1.58317060088303"></trkpt>
42 <trkpt lat="51.546998949586" lon="2.333179"></trkpt>
43 </trkseg>
44 </trk>
45 </gpx>
Thanks in advance
Lixus
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