distSpeed {diveMove}

Calculate distance and speed between locations

Description

Calculate distance, time difference, and speed between pairs of points defined by latitude and longitude, given the time at which all points were measured.

Usage

distSpeed(pt1, pt2, method = c("Meeus", "VincentyEllipsoid"))

Arguments

pt1

A matrix or data.frame with three columns; the first a POSIXct object with dates and times for all points, the second and third numeric vectors of longitude and latitude for all points, respectively, in decimal degrees.

pt2

A matrix with the same size and structure as pt1.

method

character indicating which of the distance algorithms from geosphere-package to use (only default parameters used). Only Meeus and VincentyEllipsoid are supported for now.

Value

A matrix with three columns: distance (km), time difference (s), and speed (m/s).

Author(s)

Sebastian P. Luque [e-mail]

Examples

## Using the Example from '?readLocs':
utils::example("readLocs", package="diveMove",
               ask=FALSE, echo=FALSE)

## Travel summary between successive standard locations
locs.std <- subset(locs, subset=class == "0" | class == "1" |
                   class == "2" | class == "3" &
                   !is.na(lon) & !is.na(lat))
## Default Meeus method
locs.std.tr <- by(locs.std, locs.std$id, function(x) {
    distSpeed(x[-nrow(x), 3:5], x[-1, 3:5])
})
lapply(locs.std.tr, head)

## Particular quantiles from travel summaries
lapply(locs.std.tr, function(x) {
    quantile(x[, 3], seq(0.90, 0.99, 0.01), na.rm=TRUE) # speed
})
lapply(locs.std.tr, function(x) {
    quantile(x[, 1], seq(0.90, 0.99, 0.01), na.rm=TRUE) # distance
})

## Travel summary between two arbitrary sets of points
pts <- seq(10)
(meeus <- distSpeed(locs[pts, 3:5], locs[pts + 1, 3:5]))
(vincenty <- distSpeed(locs[pts, 3:5],
                       locs[pts + 1, 3:5],
                       method="VincentyEllipsoid"))
meeus - vincenty