Request for dssd: segmentedtrack design for generating tracks

[mariechill]

Is there any chance that you will implement segmentedtrack design for generating transects within the dssd package in the near future? This would be incredibly useful for large-scale ship surveys that consist of segmented systematic line transects. Distance 8.0 doesn't handle large survey areas well. It is impossible to create an appropriate coverage grid, while dssd has no issues.

I hope you will consider this! I would be grateful!

[lenthomas]

Aloha @mariechill, thanks for raising this . I've transferred your request to the dssd repo; I'll leave the package developer @LHMarshall to respond regarding implementation in this package. In the meantime, what about creating a really coarse coverage grid in DistWin? The only purpose of the coverage grid is to assess coverage, so if you're not interested in that (e.g., because you know the design is okay coverage-wise) then you can use a huge grid spacing to generate just a few coverage grid points and go from there.

[mariechill]

Aloha Len! Thank you again for another quick response!!

I was curious about investigating the coverage. Although the study area is the same, we are planning to change the orientation of our transect lines and I wasn't sure whether changing the spacing might also be necessary. We also have some additional survey days. I don't think this will be radically different from what we did before. So perhaps I don't need to dig into assessing the coverage.

I will try a coarse grid and see how that goes. I will keep you posted.

[lenthomas]

Changing the orientation should not affect coverage (for a large area where segment length is relatively small in relation to the distance from one side of the area to the other). In any case, you can assess coverage on a coarser coverage grid -- you can still have thousands of grid points and DistWin should cope -- just not 10s or 100s of thousands of grid points! Anyway, do keep us posted. A hui hou!

[LHMarshall]

@mariechill can I just confirm that you are specifically referring to the segmented trackline design (not the segmented grid)? If so you are correct that coverage can be an issue and this is why we do not recommend this design we would recommend the segmented grid design instead. The segmented grid design is available in dssd. We do not have plans to implement the segmented trackline due to the coverage issues. Hope that helps, let me know if you have any issues using it, Laura