HelioTrak Sundial Compass Calibration

Some compasses are consistently off by a few degrees or more. To check the compass of the HelioTrak sundial, point the north-south line to geographic north, then check the direction pointed by the compass.

check magnetic declination

If the compass is working perfectly, it points to a direction exactly matching the magnetic declination for your location, which you can find on a special map or by looking it up for your city. This is normal and correct operation of your compass.

If your compass is "off", it will point some number of degrees in a different direction. To calibrate your sundial to correct for this error, mark the compass direction on the flat plate when you know that the north-south line of the plate is aligned to true geographic north.

Here are three possible ways to make sure your device is aligned to true geographic north.
With the device pointing true geographical north using any of the methods above, mark the direction that the compass is pointing. Now your device compass is calibrated, taking into account both your local magnetic declination and any compass inaccuracy.

A free downloadable declination marking tool can help you draw a straight line through the compass. Print out the tool at 100% actual size and glue it to an index card or cereal box. Cut out the tool, then use it like a ruler to draw the declination line at the proper angle. Use the 5-degree tick marks on the sundial as guides for accuracy.

declination marking tool

If you go on a long trip (many hundreds of miles or km), recalibrate your compass for the new location, as magnetic declination varies from place to place.

Back to HelioTrak Sundial main page

©2021 Gray Chang
Email: HelioTrakSundial [at] gmail [dot] com