Polyline projection on a globe

[goranskular]

Hi, it would be great if polylines were projected on the globe. Now polyline is a straight line from one latlng to a second one. It is ok for greater zoom levels, but very inaccurate when zoomed out.

Is it possible that we get projected polylines?

[ibrierley]

Do you mean the points are out, or you want the line to be a curve to account for it, screenshot may be useful.

[goranskular]

Yes, I mean a projected curved line like this:

[goranskular]

this geodesic: true would be perfect (snippet from google_maps_flutter):

Polyline(
          polylineId: PolylineId(
              'uniqueid'),
          geodesic: true,
          points: [originLatLng, destinationLatLng],
          width: 3,
          color: Theme.of(context).primaryColor,
        )

[maRci002]

Can u upload flutter_map image version which is now incorrect?

[goranskular]

Incorrect Polyline(LatLng A, LatLng B):

Correct Polyline(LatLngA,...... much more points on bearing to B, LatLng B):

p.s. I made the correct one myself with a method that generates XY points on a route from point A to point B.. so polyline is not with two points: [LatLng A, LatLng B], but with XY points: [LatLng A, LatLngXY1,....LatLngB]

[maRci002]

Nice workaround.

[goranskular]

I encountered a new problem, but I already saw some issues about it :) So, this approach is not so simple.

[S-Man42]

I am using a similar solution in my app for nearly a year right now:

Drawing Geodetic Polyline.: https://github.com/S-Man42/GCWizard/blob/master/lib/widgets/tools/coords/base/gcw_map_geometries.dart#L39

I am splitting the real way into several substeps, project from start to all substeps and then I draw a polyline. The same algorithm can be used for drawing better circles keeping their radius on the projected map:

Drawing "Geodetic" Circles : https://github.com/S-Man42/GCWizard/blob/master/lib/widgets/tools/coords/base/gcw_map_geometries.dart#L81

Surely, it's not the most efficient way to do this, espessially for more general purposes. But if you like, feel free to use the code.

The problem with the... I call it overflow..., I reported this already some months ago. I would be glad to see this problem solved! https://github.com/fleaflet/flutter_map/issues/630

Maybe this could be a solution? https://github.com/fleaflet/flutter_map/issues/468

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