Retrieve a 'Google Map' that can be used as a background for plotting points and other spatial data. The purpose of using this function should be to display the map in a browser. You should check the Google terms of use http://code.google.com/apis/maps/terms.html to see if your usage of this function (the Google API that creates the maps) is permitted. The projection of the returned Raster object is 'Mercator' (unless you use lonlat=TRUE), and other spatial data may need to be transformed before it can be plotted on top of the Google map. You can use the Mercator function to transform points from longitude/latitude to Mercator. For SpatialLines and SpatialPolygons objects, use spTransform in the rgdal package. This function uses the Google static maps web-service, and is based on functions by Markus Loecher for the RgoogleMaps package. a textual locality description, or an Extent object (with longitude/latitude coordinates), or an object that can be coerced to one (such as a Raster* or Spatial* object), in any (known) coordinate system character. Additional style arguments. See http://code.google.com/apis/maps/documentation/staticmaps/#StyledMapFeatures. Note that certain style features do not work in combination with (the default) type='terrain' 1 or 2. Using 2 doubles the number of pixels returned (and thus gives you better image quality if you need a large image) vector of two integers indicating the number of columns and rows that is requested (what is returned depends on other factors as well). Maximum values are c(640, 640), so you can only select a smaller area than the default. Note that the number of pixels returned can be doubled by using scale=2 logical. If TRUE, a RasterBrick is returned with three layers (red, green, blue). This can be plotted with plotRGB If argument x is a textual locality description, the geocode function is used to retrieve the extent that should be mapped. Change the type to 'roadmap' if the map returned says 'sorry we have no imagery here', or use a larger extent. The returned RasterLayer has a Mercator projection. To plot points (or lines or polygons) on top of it, these need to be transformed first. A matrix of longitude/latitude data can be transformed with the Mercator function used in the example below. 'Spatial*' objects can be transformed with spTransform p <,- spTransform(x, '+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +no_defs') Robert Hijmans and Sebastien Rochette, based on code by Markus Loecher, Sense Networks <,markus at sensenetworks.com>, in the RgoogleMaps package Source.


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Last Modified: April 22, 2016 @ 1:07 pm