Function SpatialPixelsTopography creates an object of class SpatialPixelsTopography-class containing topographic variables for a set of points.

SpatialPixelsTopography(points, elevation, slope, aspect,
                        tolerance = sqrt(.Machine$double.eps), 
                        proj4string = CRS(as.character(NA)), round = NULL, 
                        grid = NULL)

Arguments

points

An object of class SpatialPoints-class or a numeric matrix of coordinates.

elevation

Elevation values (in m) of the points.

slope

Slope values (in degrees) of the points.

aspect

Aspect values (in degrees from North) of the points.

tolerance

Precision up to which extent points should be exactly on a grid.

proj4string

Object of class CRS in the first form only used when points does not inherit from Spatial.

round

default NULL, otherwise a value passed to as the digits argument to round for setting cell size.

grid

Grid topology using an object of class GridTopology; a value of NULL implies that this will be derived from the point coordinates.

Value

Function SpatialPixelsTopography returns an object 'SpatialPixelsTopography-class'.

Author

Miquel De Cáceres Ainsa, CREAF

Examples

data(examplegridtopography)

#Creates spatial topography pixels as a subset of points in the grid
spt = as(examplegridtopography,"SpatialPointsTopography")
cc = spt@coords
center = 5160
d = sqrt((cc[,1]-cc[center,1])^2+(cc[,2]-cc[center,2])^2)
p = which(d<3000) #Select points at maximum distance of 3km from center
spxt = SpatialPixelsTopography(spt[p], spt$elevation[p],
                              spt$slope[p],
                              spt$aspect[p])

#Alternatively, use coercing and subsetting (drop = TRUE causes grid to be recalculated) 
spxt = as(examplegridtopography, "SpatialPixelsTopography")[p, drop=TRUE]          
                              
#Display data
spplot(spxt, variable="elevation", scales=list(draw=TRUE))

spplot(spxt, variable="slope", scales=list(draw=TRUE))

spplot(spxt, variable="aspect", scales=list(draw=TRUE))