Perperdicular distances with reticles from ice/land

[Elisa Seyboth]

Dear all,

I have some data from  line-transect cetacean surveys .

Have you ever calculated perpendicular distances from reticle measurements that were not taken in relation to the horizon (i.e. were measured from icebergs or land)? I would like to do all the estimations in R, without relying on ArcGIS/QGIS/etc ...

Does anybody have some tips and/or some material to share that could help me in this process?

Many thanks,

Elisa.

--

M.Sc. Elisa Seyboth

PhD Candidate

Laboratório de Ecologia e Conservação da Megafauna Marinha - EcoMega

Instituto de Oceanografia

Universidade Federal do Rio Grande - FURG - Brasil

APECS Council Member (2016-2018) 

APECS-Brazil Member and National Committee Representative (2017-2018)

Tel.: +55(53) 32336537/981409331

[Eric Rexstad]

That's a good question for the list Elisa.  I don't know of code to do what you ask, but hopefully some member of the list might be able to help you out.

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[Elisa Seyboth]

Thanks, Eric! Hope someone can help with this issue :)

2018-06-01 12:22 GMT-03:00 Eric Rexstad <er...@st-andrews.ac.uk>:

That's a good question for the list Elisa.  I don't know of code to do what you ask, but hopefully some member of the list might be able to help you out.

------ Original Message ------

From: "Elisa Seyboth" <elisas...@gmail.com>

To: distance-sampling@googlegroups.com

Sent: 01/06/2018 15:44:58

Subject: [distance-sampling] Perperdicular distances with reticles from ice/land

Dear all,

I have some data from  line-transect cetacean surveys .

Have you ever calculated perpendicular distances from reticle measurements that were not taken in relation to the horizon (i.e. were measured from icebergs or land)? I would like to do all the estimations in R, without relying on ArcGIS/QGIS/etc ...

Does anybody have some tips and/or some material to share that could help me in this process?

Many thanks,

Elisa.

--

M.Sc. Elisa Seyboth

PhD Candidate

Laboratório de Ecologia e Conservação da Megafauna Marinha - EcoMega

Instituto de Oceanografia

Universidade Federal do Rio Grande - FURG - Brasil

APECS Council Member (2016-2018) 

APECS-Brazil Member and National Committee Representative (2017-2018)

Tel.: +55(53) 32336537/981409331

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[Res. Ass. Uğur ÖZSANDIKÇI]

"In coastal surveys, the horizon is often obscured by land. In this case, the observer measures the declination from the shoreline to the sighting (using binocular reticles) while the vessel’s captain simultaneously measures the distance to the shoreline in the same direction via RADAR (a laser-range finder can also be used if close to shore). In analysis, you can add the expected declination (in reticles) from the horizon to the shoreline given its distance to your observed declination, and then convert this total declination to a true distance to the animals (e.g. Barlow, 1995; Lerczak & Hobbs, 1998). Distance to land can also be measured from the boat position (if that is known accurately, e.g. via GPS) using accurate paper or digital charts. Even inexpensive, hand-held GPS units are accurate enough for this purpose without differential correction (e.g. Garmin eTrex; over 48 hours 50% of fixes were <3.8 m of the true position, and 95% were <6.7 m; Wilson, 2007)."  Dawson, Steve; Wade, Paul; Slooten, Elisabeth; and Barlow, Jay, "Design and field methods for sighting surveys of cetaceans in coastal and riverine habitats" (2008). Publications, Agencies and Staff of the U.S. Department of Commerce. 255. http://digitalcommons.unl.edu/usdeptcommercepub/255

I hope it will be helpfull... 

1 Haziran 2018 Cuma 17:45:00 UTC+3 tarihinde Elisa Seyboth yazdı:

[Elisa Seyboth]

Dear,

thank you very much for sending that information!

The challenge will be to create a code to try to make the

measurements in R :)

Cheers,

Elisa.

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[Gemma Veneruso]

Hi Elisa,

 

Apologies if this email comes too late. I have some R code to calculate distance of objects using binocular reticules using land as a reference based on formula developed by Lerczak and Hobbs 1998. What you need first is code to calculate the distance between the boat and land for each detection which was calculated by a colleague and then my code will do the rest. If you would like a copy of this feel free to get in contact.

 

Best wishes,

 

Gemma Veneruso

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--

M.Sc. Elisa Seyboth

 

PhD Candidate

Laboratório de Ecologia e Conservação da Megafauna Marinha - EcoMega

Instituto de Oceanografia

Universidade Federal do Rio Grande - FURG - Brasil

APECS Council Member (2016-2018) 

APECS-Brazil Member and National Committee Representative (2017-2018)

 

Tel.: +55(53) 32336537/981409331

 

 

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[Ruth Esteban]

Hi Gemma, 

I would be interested in that R code,would you please send it to me?

Best wishes

Ruth