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Adjusting for ship speed on transects

Grant RW Humphries, July 3, 2015

Heya everyone,

I'm looking for some help - I'm working on some ship transect data with variable ship speeds along the transects. It's a common problem, but I haven't come across any studies that adjust calculated densities due to ship speed.

What I'm looking for is any studies that use the mean ship speed to correct density calculations, etc..

Also, if anyone has some really good abundance modeling reference suggestions, that would be appreciated too.

THANKS! Grant Humphries

Comments ( 2 )

Eric Woehler

Eric Woehler

Hey Grant

have a look at a number of Ainley and Spear articles that looked specifically at the influence of ship speed on density calculations. They used vector analyses to adjust counts to densities as a function of vessel speed and relative angles of vessel and birds. One of the papers was able to reconcile population estimates from at-sea densities with colony based estimates.

There are perhaps 4 or 5 papers by Dave/Larry to look at/consider using. There were similar papers/analyses by Jan van Franeker. All papers were early-90s onwards from memory.

Let me know if you have trouble getting PDFs of them. good luck! E

Mark Tasker

Mark Tasker


I am puzzled as to your lack of success at tracking down any relevant papers. Every single one of the UK Seabirds at Sea reports and papers adjusted their calculated densities based on ship's speed. We worked on strip transects of (usually) 300m wide x whatever distance was travelled in (usually) 10 minutes. Tasker et al (1984) also used this - and it discusses snapshot approach for flying birds that needs ship speed built in. We did not use mean ship speed, but actual ship speed. Cheers Mark