Use AKsf boundaries in GMT

AKsf provides the fisheries geometry; GMT provides its own cartography. write_gmt() writes GMT/OGR polygon files through sf/GDAL. GMT is optional and is needed only when rendering a GMT figure. This preserves your GMT shell workflow rather than reimplementing GMT in R.

Export from R

Show/hide R code

library(AKsf)
write_gmt(get_fmp_areas("BSAI_GF"), "bsai.gmt")
write_gmt(get_fmp_areas("GOA_GF"), "goa.gmt")
write_gmt(get_reporting_areas(), "reporting.gmt")
write_gmt(get_coast(), "land.gmt")

The output uses WGS84 longitude/latitude, retains identifiers and polygon holes, and splits multipart features and dateline crossings. Attributes repeat for each polygon part; rows are not necessarily unique areas. Existing files require overwrite = TRUE. The sf installation needs GDAL’s writable GMT driver.

Render with GMT 6

Install GMT using its platform instructions (for example, brew install gmt on macOS). PNG/PDF output also needs Ghostscript. Run these commands in the directory containing the exported files:

Show/hide shell code

gmt begin alaska-fmp png
  gmt set FONT_TITLE 16p FONT_ANNOT_PRIMARY 9p MAP_FRAME_PEN 1p
  gmt basemap -R170/235/48/72 -JB-154/50/55/65/18c -Baf -BWSne+t"Alaska groundfish FMP reference areas"
  gmt plot bsai.gmt -Glightblue -W0.4p,steelblue -l"BSAI groundfish"
  gmt plot goa.gmt -Glightgoldenrod -W0.4p,darkorange -l"GOA groundfish"
  gmt plot reporting.gmt -W0.2p,gray40
  gmt plot land.gmt -Ggray90 -W0.2p,gray50
  gmt legend -DjTR+w4.5c+o0.3c -F+gwhite+p0.25p
gmt end

This is a GMT Albers map with central meridian 154°W, latitude of origin 50°N, and standard parallels 55°N/65°N. Those parameters resemble AKsf’s default, but GMT’s geographic plotting is not a declaration that this figure is an EPSG:3338 dataset: exported coordinates are WGS84. The region uses 170–235°E so the Aleutians cross 180° continuously. Do not relabel projected metre coordinates as longitude/latitude or discard polygon-hole markers.

The example uses bundled land rather than a remote coastline download. For higher-resolution basemaps, use GMT’s coastline/relief facilities or akgfmaps sources with their own provenance. The fisheries boundaries remain AKsf’s cartographic references, regardless of rendering tool.

Environmental grids

Use coldpool’s temperature products as the environmental source. terra can write a chosen upstream raster to a GMT-readable grid format such as GeoTIFF; GMT’s grdimage can render it when GMT has GDAL support. Preserve its native CRS, missing values, registration, and units; an arbitrary projected grid is not a longitude/latitude grid. Check gmt grdinfo and transform explicitly if the GMT workflow requires geographic coordinates. Do not recompute the published cold-pool index from an FMP mask.

See the repository’s AFSC integration guide for overlap with coldpool, akgfmaps, and navmaps. AKsf does not duplicate their survey design, environmental models, or navigation exporters.

Survey and seasonal catch case study

The Eastern Bering Sea survey and fishery maps article shows how AKsf geometry supports survey comparisons and catch columns over GMT Earth Relief. It includes shaded log-value views, matched map planes, an exaggerated terrain example, and simple input/update instructions. The archived figures use supplied observations; the article’s executable example uses clearly labeled synthetic catch points and runs offline.