Some rambling

Jigger-Fishtrawl overlap

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Was asked about the overlap between jiggers and fishtrawlers. Here is a quick hash based on data from 2008-2024 with the effort (time) expressed on a log scale.

Einar Hjörleifsson

Points in polygon: Via duckdb & arrow

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Just a short note here towards the road of having ‘spatial’ parquet files, one set being POINTS the other POLYGONS and doing a point-in-polygon witin duckdb. Now I say ‘towards the road’ because here the final solution is not provided!

Einar Hjörleifsson

On gridding

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This post originated in that moi wanted to check if the code ‘x = lon %/% dx * dx + dx/2’ would give the same results as CSquare gridding as implemented in {vmstools}. Short answer is no. The former is more consistent, always resulting in binning such that if a value is exactly at ‘grid’-boundary it is included if on the lower boundary, excluded if on the upper boundary. In the {vmstools}-csquare case this depends on the global quarters. Now, somebody may argue that the practical consequences is miniscule and I would fully concur :-) Say so because a very small portion of real numeric data will be exactly on the grid boundary as focused on here. Leaving the devil in the details aside, the main message is that using ‘x = lon %/% dx * dx + dx/2’ is OK to use within R, arrow or duckdb code workflow. Why is this important? Because in the latter two workflows a csquare algorithm is not available/implemented.

Einar Hjörleifsson

On anonymity

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library(tidyverse)
library(duckdbfs)
library(mapdeck)
library(tictoc)
library(h3)
tic()
tic()
q <-
  open_dataset(here::here("data/ais/trail")) |> 
  filter(.cid > 0,      …

Einar Hjörleifsson

Distribution of seaweed and kelp harvesting

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I was asked what AIS data can inform us about distribution of seaweed and kelp harvesting. Normally one would filter out information from the logbooks and landings database with respect to vessels and dates of trips and then plot all records that fall within such trips. But since that is lacking here we, for the time being we filter the AIS for some suspeted vessels as a first go. If only to show what is feasable. For now the statistics shows the number of distinct years a hexagon grid was visited by a vessel.

Einar Hjörleifsson

Working with AIS data using {duckdb} and {h3}

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Must admit that I have not fully grasped the duckdb-concept but what I have explored is magical. The main R-package is {duckdb} but {duckdbfs} provides a nice wrapper for making connection to files easier (similar to the {arrow}) package. On top of it {duckdbfs} has some intriguing spatial function. Here a little exploration of the AIS data is made to put the feature to a test.

Einar Hjörleifsson

Seaweed, fishing and beautiful creatures

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I was asked to provide a map of net fishing in shallow waters, sea-weed bed distribution, seal rutting areas and coastal bird distributions. Here is the code behind that delivery.

Einar Hjörleifsson

Fishtrawl footprint - by proportion of total catch

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One of the characteristics of fish bottom trawling is that the catch is taken in a very limited area of the total trawl footprint. E.g. about 60% of the catch is taken in 10% of the total area. Here we ‘look’ at this from the other angle and show show the areas were less than 5%, 10%, .. percentage of the total catch is taken. These kind of acrobatics may be a foundation for some intriguing discussions.

Einar Hjörleifsson

About depth

areas

I was asked today how many square kilometers of the Icelandic EEZ was below 1000 meters depth. Here a short code-note of the answer is provided.

Einar Hjörleifsson

leaflet addGeotiff

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Just a quick note on using geotiff file in leaflet

Einar Hjörleifsson

Norwegian AIS data

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When it comes to commerical fisheries data, the Norwegians are quite liberal. Actually extremely liberal. They basically have everything accessible. Here a quick code hash is provided as a case in point, showing the longline fleet individual hauling operation in 2022 to 2024.

Einar Hjörleifsson

Lumpsucker fisheries - effort distribution

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A little overview of the distribution of lumpsucker fisheries and area closures. Turns out that there is not much of an overlap!

Einar Hjörleifsson