Open AccessThe Use of Global Positioning Systems to Record Distances in a Helicopter Line‐Transect Survey
Author(s) -
MARQUES TIAGO A.,
ANDERSEN MAGNUS,
CHRISTENSENDALSGAARD SIGNE,
BELIKOV STANISLAV,
BOLTUNOV ANDREI,
WIIG ØYSTEIN,
BUCKLAND STEPHEN T.,
AARS JON
Publication year - 2006
Publication title -
wildlife society bulletin
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.578
H-Index - 82
eISSN - 1938-5463
pISSN - 0091-7648
DOI - 10.2193/0091-7648(2006)34[759:tuogps]2.0.co;2
Subject(s) - distance sampling , global positioning system , inclinometer , geodesy , declination , line (geometry) , trigonometry , sampling (signal processing) , computer science , remote sensing , transect , statistics , geography , geology , mathematics , telecommunications , physics , oceanography , geometry , astronomy , detector
Methods that allow unbiased estimation of animal abundance are increasingly demanded in management and conservation. The use of these methods should respect their assumptions. The need for accurate distance measurements in distance‐sampling surveys is stressed. Here we present 2 alternative methods for measuring distance from a line to an object during helicopter surveys: 1) using a Global Positioning System (GPS) unit, with distances measured using appropriate software; and 2) recording declination angles and altitudes, using basic trigonometry to obtain the appropriate distances. These are compared to distances measured by a laser rangefinder (assumed to be true distances). The effect of the different errors on estimated densities is assessed by simulation. The GPS method appeared to be very accurate, while a potential downward bias in estimated density could be present if the inclinometer method is used. We discuss the implication for wildlife studies of using different measurement methods leading to different errors.