You need to be working in map/pixel coordinates (x, y), not geographic
coordinates (lat, lng). The projection from the latter to the former
is Mercator, modulo some linear tweaks of the y coordinate axis (see
<http://en.wikipedia.org/wiki/Mercator_projection>). In Mercator,
coordinate changes Δx and Δy are designed to be the same over short
distances, and therefore so will be the azimuth ~ arctangent (Δx/Δy).
I haven't tried this, but I think you can do the following: convert
your (lat, lng) to pixels with
p:GPoint = map.fromLatLngToContainerPixel(GLatLng(lat, lng))
Then with your chosen displacement in pixels, calculate your new x and
y with
x = p.x + disp * Math.sin(azimuth)
y = p.y - disp * Math.cos(azimuth)
and then calculate the new marker position with
marker:GLatLng = map.fromContainerPixelToLatLng(GPoint(x, y))
-- Andy
On May 30, 3:54 pm, JavaJive <[email protected]> wrote:
> I am trying to create a marker to show where to point a satellite
> dish....
>
> I have a routine that works out the azimuth for the dish, and under
> Open Layers I take the point representing the dish site, construct
> another due north by the length of the marker line, and then rotate
> the second about the first by the required azimuth ...
> var p1 = new OpenLayers.Geometry.Point( aLonLat.lon, aLonLat.lat );
> var p2 = new OpenLayers.Geometry.Point( aLonLat.lon, aLonLat.lat +
> markerLength );
> p2.rotate( -anAzim, p1 );
> ... and this gives the correct azimuth. ....
>
> In the Google API, I can get the required direction by creating the
> second point on the equator beneath the destination satellite ...
> createDragLineMarker( loc, new google.maps.LatLng(0, 28.2) );
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