perpDists {Rdistance}

Compute off-transect distances from sighting distances and angles

Description

Computes off-transect (also called 'perpendicular') distances from measures of sighting distance and sighting angle.

Usage

perpDists(sightDist, sightAngle, data)

Arguments

sightDist

Character, name of column in data that contains the observed or sighting distances from the observer to the detected objects.

sightAngle

Character, name of column in data that contains the observed or sighting angles from the line transect to the detected objects. Angles must be measured in degrees.

data

data.frame object containing sighting distance and sighting angle.

Details

If observers recorded sighting distance and sighting angle (as is often common in line transect surveys), use this function to convert to off-transect distances, the required input data for F.dfunc.estim.

Value

A vector of off-transect (or perpendicular) distances. Units are the same as sightDist.

References

Buckland, S.T., Anderson, D.R., Burnham, K.P. and Laake, J.L. 1993. Distance Sampling: Estimating Abundance of Biological Populations. Chapman and Hall, London.

See Also

dfuncEstim

Examples

# Load the example dataset of sparrow detections from package
data(sparrowDetectionData)
# Compute perpendicular, off-transect distances from the observer's sight distance and angle
sparrowDetectionData$perpDist <- perpDists(sightDist="sightdist", sightAngle="sightangle",
                                           data=sparrowDetectionData)