pointCircle: Create points in a circle around an existing point

In mpio-be/windR: Analysis of tracking data in relation to wind

Description

This function caclulates the position of points in a circle around a start point. The circle is based on the distance of the second point that is provided. This allows for example to compare the the temperature conditions in all directions (i.e. is a bird flying in the direction of warmer temperatures).

Usage

pointCircle(lon, lat, lon2, lat2, pointN = 36, PROJ)

Arguments

lon	Longitude of point 1
lat	Latitude of point 1
lon2	Longitude of point 2
lat2	Latitude of point 2
pointN	The number of points that should be created on the circle
PROJ	The projection of the points (should be equal area)

Value

A table with the real point and estimated points around it

Examples

x        = 10
y        = 10
x2       = 100
y2       = 600
pointN   = 36
PROJ     = '+proj=laea +lat_0=90 +lon_0=-156.653428 +x_0=0 +y_0=0 +datum=WGS84 +units=m
            +no_defs +ellps=WGS84 +towgs84=0,0,0 '

dp = pointCircle(x, y, x2, y2, pointN = 36, PROJ)

# visualization of the example
library(sp)
dp = as.data.table (dp)
PS  = SpatialPointsDataFrame(dp[1, .(x,y)], dp[1, .(pointType)],
                             proj4string = CRS(PROJ), match.ID = TRUE)
PS2 = SpatialPointsDataFrame(dp[, .(x2,y2)], dp[, .(pointType)],
                             proj4string = CRS(PROJ), match.ID = TRUE)

plot(PS2[PS2@data$pointType == 'estimated', ], col = 'red')         # estimated points
plot(PS2[PS2@data$pointType == 'real', ], col = 'blue', add = TRUE) # second point
plot(PS, add = TRUE)                                                # first point

mpio-be/windR documentation built on Feb. 2, 2020, 10:04 a.m.