lonlat2planar = function ( x, proj.type, input_names=c("lon", "lat"), newnames = c("plon", "plat") ) {
#\\ convert lon/lat to a projected surface using proj
#\\ proj.type can be an internal code such as "utm20" or a proj4 argument
#\\ output scale is defined in the +units=km (default for bio) or +units=m (default for proj)
# first try an internal conversion /lookup for CRS
proj4.params = try( CRS( lookup.projection.params(proj.type) ), silent=TRUE )
# if internal lookup does not work then try to directly pass to CRS
if (is.null(proj.type)) {
print( proj.type )
warning( "Projection not recognised")
}
if ( "try-error" %in% class( proj4.params) ) {
if (!is.null(proj.type)) proj4.params = try( CRS( proj.type ), silent=TRUE )
}
if ( "try-error" %in% class( proj4.params) ) {
if (!is.null(proj.type)) proj4.params = try( CRS( as.character(proj.type) ), silent=TRUE )
}
if ( "try-error" %in% class( proj4.params) ) {
print( proj.type )
warning( "Projection not recognised")
}
crsX = CRSargs( proj4.params)
if ( ! grepl("units", crsX) ) {
print (crsX)
stop( "The proj4 CRS requires an explicit +units=km ")
}
y = rgdal::project( as.matrix(x[,input_names]), proj=crsX , inv=F )
colnames(y) = newnames
for (i in 1:length( newnames)) {
if ( newnames[i] %in% colnames(x) ) x[, newnames[i]] = NULL
}
x = cbind(x,y)
return (x)
}
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