Issue with definition of Barrier_scaling used in applications of Barrier mesh option

[N-DucharmeBarth-NOAA]

I had a look in the code and see where Barrier_scaling is defined in make_data() on line 1014 as:

Return[['Barrier_scaling']] = c(0.2, 1)

and where it enters the VAST code as c on lines 28-30 of VAST_v13_1_0.cpp:

  vector <Type> range(2);
  range(0) = sqrt(8.0)/kappa*c(0);
  range(1) = range(0)*c(1);

Barrier_scaling should be c(1,0.2) following the original Brevik paper (Equation 3) and line 62 from this Brevik & Skaug example.

Additionally, the fraction of the spatial range of the decorrelation distance applied in the presence of a barrier could be user specified (e.g. Return[['Barrier_scaling']] = c(1, range_fraction)). range_fraction could be defined as a formal argument to make_data() with a default value of 0.2.

[James-Thorson-NOAA]

Nicholas,

Thanks for pointing this out! Using the Pacific Islands grid and barrier vs. non-barrier fits that you provided, I can confirm that the previous implementation was a bug, and that I need to change the Barrier_scaling vector as you say.

I'll aim to do a hotfix soon (likely next week), and will leave this open until then.

[James-Thorson-NOAA]

@N-DucharmeBarth-NOAA

Do you mind looking at my lastest push for the main branch of VAST to see if it fits your expectations? I added Range_fraction as an option to pass via settings$Options (with reference documentation updated) but changed the default as noted.

If it looks good (or you don't have time), please respond and I'll make a numeric release

[N-DucharmeBarth-NOAA]

Hi Jim,
I took a look at the latest code change and it looks good to me. I'll test it on my next model runs. Thank you for making that update!
Best,
Nicholas