perpDists function

Compute off-transect distances from sighting distances and angles

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

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.

Returns

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

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 dfunc.estim.

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)

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