getWikiMedia.ImageInfo function fetches the EXIF (Exchangeable image file format) data via the Wikimedia API for any donated image. The resulting EXIF data (named list) can then be further used to construct an object of class "SpatialPhotoOverlay", which can be parsed to KML.
check_projection
(Package: plotKML) :
Extracts the proj4 parameters and checks if the projection matches the referent CRS
Function parse_proj4 gets the proj4 string from a space-time object and check_projection checks if the input projection is compatible with the referent projection system. The referent system is by default the longlat projection with WGS84 datum (KML-compatible coordinates).
A class containing input and output maps containing multiple realizations of the same feature. Objects of this class can be directly visualized in Google Earth by using the plotKML-method.
Writes sp classes "SpatialGrid" or "SpatialPixels" to PNG images and makes a KML document (ground overlays). Target attributes can be specified using aesthetics arguments (e.g. "colour").
Writes any Spatial* object (from the sp package) or Raster* object (from the raster package) to a KML file via the plotKML.fileIO environment. Various aesthetics parameters can be set via colour, alpha, size, shape arguments. Their availability depends on the class of the object to plot.
reproject
(Package: plotKML) :
Methods to reproject maps to a referent coordinate system (WGS84)
This wrapper function reprojects any vector or raster spatial data to some referent coordinate system (by default: geographic coordinates on the World Geodetic System of 1984 / WGS84 datum).
providing 
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