horizon: Horizon Angle Computation

In ecor/horizons: How to get horizon profiles from some points with an elevation raster map.

Horizon Angle Computation

Description

This function calculates the horizon angle of given points using an elevation raster map

Usage

horizon(
  r,
  points = data.frame(x = c(0, (xmin(r) + xmax(r))/2), y = c(0, (ymin(r) + ymax(r))/2)),
  adjust.zero = TRUE,
  n = 8,
  radius = 50000,
  names = NULL
)

Arguments

r	Raster* object contianing the Digital Elevation Map
points	data frame containing x and y coordinaates
adjust.zero	logical value. It it is TRUE, negative horizon angle are not considered.
n	number of directions used. Default is 8.
radius	see xyFrom2PointLine
names	names of the points

Value

It returns a list of data frames. A list element represents a examined point and contains n horizon angles for all n direction. The vertical horizon angle are conterclockwise referred to the horizontal axis and are expressed in degree units.

See Also

xyFrom2PointLine

Examples

library(horizons)
library(raster)

# First Example: Spare Hull
side <- 5010
n <- 501

values <- array(NA,c(n,n))
coord <- (1:n)/n*side-side/2
values <- outer(X=coord,Y=coord,FUN=function(x,y) {(x^2+y^2)^0.5})

r <- raster(values, crs=NA,xmn=-side/2,xmx=side/2,ymn=-side/2,ymx=side/2)


xpp <- c(-side/3,0,0,0,side/3)
ypp <- c(0,-side/3,0,side/3,0)
idp <- c("A","B","O","C","D")
points <- data.frame(x=xpp,y=ypp,id=idp)

hor <- horizon(r,points=points)
names(hor) 
points$id





# Second Example 

dem <- raster(system.file("dem/dem_rendena.asc",package="horizons"))

horizons <- horizon(dem)

ecor/horizons documentation built on Jan. 4, 2024, 6:25 p.m.