//newTilePolygon creates the geos polygon for a given tile.
func newTilePolygon(level, x, y int) (*geos.Geometry, error) {
latDeg := raster.Y2Lat(level, y)
lonDeg := raster.X2Lon(level, x)
lat2Deg := raster.Y2Lat(level, y+1)
lon2Deg := raster.X2Lon(level, x+1)
return geos.NewPolygon(
[]geos.Coord{
geos.NewCoord(lonDeg, latDeg),
geos.NewCoord(lon2Deg, latDeg),
geos.NewCoord(lon2Deg, lat2Deg),
geos.NewCoord(lonDeg, lat2Deg),
geos.NewCoord(lonDeg, latDeg),
})
}
// Searches the R-Tree to find the place corresponding to the given lat,lng
// First uses the R-Tree which contains only the bounding boxes of the
// entities, and then refine the result using the actual geometry of the entity.
func reverseGeocode(rt *rtreego.Rtree, lat, lng, precision float64) (*GeoData, error) {
var results []rtreego.Spatial
// First search the R-Tree
rpt := rtreego.Point{lng, lat}
results = rt.SearchIntersect(rpt.ToRect(precision / 2.))
if len(results) == 0 || results[0] == nil {
nn := rt.NearestNeighbor(rpt)
if nn == nil {
return nil, ErrNoMatchFound
} else {
results = []rtreego.Spatial{nn}
}
}
// Then check with the actual geometry of the entity
mindist := math.MaxFloat64
var argmindist *GeoData
gpt, _ := geos.NewPoint(geos.NewCoord(lng, lat))
for _, res := range results {
if res == nil {
break
}
obj, _ := res.(SpatialData)
geod := obj.GetData()
inside, _ := geod.Geom.Contains(gpt)
if inside {
return geod, nil
}
dist, _ := gpt.Distance(geod.Geom)
if dist < mindist {
mindist = dist
argmindist = geod
}
}
if mindist < precision {
return argmindist, nil
}
return nil, ErrNoMatchFound
}