`SpatialPixelsTopography.Rd`

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)
```

- 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.

Function `SpatialPixelsTopography`

returns an object '`SpatialPixelsTopography-class`

'.

```
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))
```