Convert GPS coordinate to ArcGIS x,y point?

Question

I'm trying to plot some AGSSimpleMarkerSymbol's in a AGSGraphicsLayer. The issue I'm running into is that the data I'm starting with are GPS coordinates (lat/lon). I'm using AGSPoint to plot the data, however, AGSPoint wants x and y points - not lat/lon.

My question is, how do I convert my GPS coordinates to x and y points?

Answer 1

Basically you want to use the projectGeometry method from the AGSGeometryEngine class to convert from the GPS coordinate system to the coordinate system used by your map. Use the defaultGeometryEngine for this.

Assuming your GPS is giving you WGS-84 coordinates you could do something like this:

CLLocation* gpsLocation = ....

// create a AGSPoint from the GPS coordinates
AGSPoint* gpsPoint = [[AGSPoint alloc] initWithX:gpsLocation.coordinate.longitude
                                               y:gpsLocation.coordinate.latitude
                                spatialReference:[AGSSpatialReference wgs84SpatialReference]];

AGSGeometryEngine* engine = [AGSGeometryEngine defaultGeometryEngine];

// convert GPS WGS-84 coordinates to the map's spatial reference
// (assuming self.mapView is your AGSMapView for your map)
AGSPoint* mapPoint = (AGSPoint*) [engine projectGeometry:gpsPoint 
                                      toSpatialReference:self.mapView.spatialReference];

Answer 2

The two numerals before the decimal point and those after are minutes, the two/three numerals at the front are degrees, i.e. 32 degrees, 46.4270 minutes, 117 degrees, 04.3785 minutes, etc. You can convert these to decimal degrees after loading doesn't need three lines but hopefully this makes the process clearer