Multiplier Activity

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Gregory Pap

Nov 11, 2022, 5:42:57 AM11/11/22
to distance-sampling
I have a question about CT distanse sampling.
When a camera is operating 24h constandly and the survey is targeting mulple species, how can i calculate the sample fraction of activity?
Thank you! 

Eric Rexstad

Nov 11, 2022, 6:47:19 AM11/11/22
to Gregory Pap, distance-sampling

If you intend to produce species-specific density estimates from analysis of your survey data, I would think you would want to produce species-specific activity measures for the individual species of interest.

To do this, you would analyse data for each species separately and use the make_activity_fn()​ in the Distance R package as described in this link

Truncation decisions. As described by Howe et al. ():. a paucity of observations between 1 and 2 m but not between 2 and 3 m, so we left-truncated at 2 m. Fitted detection functions and probability density functions were heavy-tailed when distances >15 m were included, so we right truncated at 15 m.
Have I answered the question you were asking?

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Eric Howe

Nov 11, 2022, 10:46:50 AM11/11/22
to distance-sampling
"Sample fraction" usually refers to the fraction of a circle monitored, as the angle of view of the camera in degrees / 360 (theta). It can be included in the calculation of point-specific effort as describe in Howe et al. 2017,  or, if theta is the same for all cameras, as the sample fraction multiplier. Activity level, estimated as described by Eric R, can also be included as a "multiplier", but isn't usually referred to as the sample fraction multiplier. "Sample fraction" usually refers to situations where < a complete circle is monitored.

Eric H

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