Distance sampling: Difference between revisions

Revision as of 21:09, 24 March 2019

Revision as of 21:27, 24 March 2019

Line 1:

'''Distance sampling''' is a widely used group of closely related methods for estimating the [[population density|density]] and/or [[abundance (ecology)|abundance]] of [[population]]s. The main methods are based on line [[transect]]s or [[point transect]]s.<ref name=buckland1993>Buckland, S. T., Anderson, D. R., Burnham, K. P. and Laake, J. L. (1993). ''Distance Sampling: Estimating Abundance of Biological Populations''. London: Chapman and Hall. {{ISBN|0-412-42660-9}} [http://www.colostate.edu/Dept/coopunit/download.html Online version]</ref><ref name=buckland2001>{{cite book|last1=Buckland|first1=Stephen T.|first2=David R.|last2=Anderson|first3=Kenneth Paul|last3=Burnham|first4=Jeffrey Lee|last4=Laake|first5=David Louis|last5=Borchers|first6=Leonard|last6=Thomas|title=Introduction to distance sampling: estimating abundance of biological populations|year=2001|publisher=Oxford University Press|___location=Oxford}}</ref> In this method of sampling, the data collected are the distances of the objects being surveyed from these randomly placed lines or points, and the objective is to estimate the average density of the objects within a region.<ref>Everitt, B. S. (2002) ''The Cambridge Dictionary of Statistics'', 2nd Edition. CUP {{ISBN|0-521-81099-X}} (entry for distance sampling)</ref>

==Basic line transect methodology==

Line 26:

|-

! [[Failure_rate#hazard_function|Hazard-rate]]

| {{math|1-exp(-(''|y|''/''σ'')^-b)}}

|-

! [[Exponential distribution|Negative exponential]]

| {{math|exp(-''aya|y|'')}}

|}

Here ''w'' is the overall detection truncation distance and ''a'', ''b'' and ''σ'' are function-specific parameters. The half-normal and hazard-rate functions are generally considered to be most likely to represent field data that was collected under well-controlled conditions. InDetection contrast,probability bothappearing theto uniformincrease andwith negative exponential functions assume that detection probability does not drop offdistance from the centertransect line but remains at the same level (uniform) or increases (negative exponential); these circumstances may be indicative ofindicate problems with data collection or survey design.<ref name=buckland2001/>

== References ==