Hamish MacMillan

Tip of the Week #13 - Adjusting for Magnetic Declination when Capturing Offsets in TerraFlex

Blog Post created by Hamish MacMillan on Feb 20, 2020

We have had a few questions from users about how to adjust for magnetic declination when capturing offsets in TerraFlex. If an adjustment is not made for magnetic declination, it can cause the location of features as measured by the laser to be incorrect.


What is Magnetic Declination?

Magnetic declination refers to the offset between True North (geographic North Pole) and Magnetic North (the direction the North end of a compass will point based on the Earth's magnetic field). This offset will vary based on your location and will change over time. Wikipedia has a good article on magnetic declination here if you want to learn more


How do I calculate magnetic declination for my area?

NOAA's National Center for Environmental Information has published a tool here that allows you to calculate the magnetic declination for your area. Here in Christchurch, New Zealand the offset between True North and Magnetic North is 24° 6' East


Configuring magnetic declination for a LTI TruPulse 360 Series laser rangefinder

TerraFlex expects the azimuth/bearing reading that is output by the TruPulse 360 to be True North, so to get the right offset results in TerraFlex you need to set the magnetic declination in your TruPulse 360 laser rangefinder. The magnetic declination can not be set in TerraFlex. The TruPulse 360 User Manual has instructions for setting magnetic declination, starting on Page 24.