Blurred contours

Use the contour mark’s blur option for smoother isolines.

Plot.contour(ca55, {x: "LONGITUDE", y: "LATITUDE", fill: "MAG_IGRF90", blur: 4}).plot({color: {type: "diverging"}})

const ca55 = FileAttachment("data/ca55-south.csv").csv({typed: true}).then(display);