RgoogleMaps (version 1.1.9.3)

XY2LatLon: computes the centered coordinate transformation from lat/lon to map tile coordinates

Description

The function XY2LatLon(MyMap, X,Y,zoom) computes the coordinate transformation from map tile coordinates to lat/lon given a map object.

Usage

XY2LatLon(MyMap, X, Y, zoom)

Arguments

MyMap

map object

X

latitude values to transform

Y

longitude values to transform

zoom

optional zoom level. If missing, taken from MyMap

Value

• properly scaled and centered (with respect to the center of MyMap ) coordinates
• lon
  longitude
• lat
  latitude

See Also

LatLon2XY Tile2R

Examples

#quick test:

  zoom=12;MyMap <- list(40,-120,zoom);
  LatLon <- c(lat = 40.0123, lon = -120.0123);
  Rcoords <- LatLon2XY.centered(MyMap,LatLon["lat"],LatLon["lon"])
  newLatLon <- XY2LatLon(MyMap, Rcoords$newX, Rcoords$newY)
  max(abs(newLatLon - LatLon));

#more systematic:
 for (zoom in 2:10){
   cat("zoom: ", zoom, "");
   MyMap <- list(40,-120,zoom);
   LatLon <- c(lat = runif(1,-80,80), lon = runif(1,-170,170));
   Rcoords <- LatLon2XY.centered(MyMap,LatLon["lat"],LatLon["lon"])
   newLatLon <- XY2LatLon(MyMap, Rcoords$newX, Rcoords$newY)
   if(max(abs(newLatLon - LatLon)) > 0.0001) print(rbind(LatLon, newLatLon));
 }