On May 1, a small clump of Coreopsis blooming at the edge of a Brazoria County ditch brought an immediate smile. The combination of flower and buds looked remarkably like a ship’s binnacle, with its compass in the middle and correcting balls at either side.
Local distortions of the earth’s magnetic field can make a compass inaccurate for navigational use, but some of the distortions, particularly those caused by the ship itself, remain fairly constant. Those errors are corrected by using small adjuster magnets, iron rods, or compensating balls incorporated into the binnacle, like those shown above. While the devices themselves also distort the local magnetic field around the compass, they’re arranged in a way that corrects compass headings.
The process of correcting a compass using various devices, called ‘swinging the compass,’ is complex. Even after adjustments are made, residual errors exist. So-called ‘deviation cards’ record known compass errors for all headings of the ship, and help to make accurate navigation possible.
Given our current conditions, I’d say this Coreopsis compass was perfectly adjusted; we’re making way, and the shore of summer is in sight.