The aim line shows where your boat is heading on the chart. You can choose which source is used to calculate the direction.
To select your heading source for the aim line, go to Settings > Chart, scroll to "Show aim line" and search for the "Heading Source" option
Orca allows you to select three heading options:
GPS course
Compass
Both
What does each heading source show on the chart?
The aim lines you see depend on the heading source option you choose
GPS Course: Shows your Course Over Ground (COG), which is the actual direction your boat is moving across the water, taking into account current and wind drift
This is best when you want to see where you are actually going
Compass: Shows your heading, which is the direction your boat is physically pointing, regardless of drift
This is best when you want to see where your boat is oriented
These options display as a single solid black line on the chart:
Both: Shows GPS course and compass at the same time. COG appears as a solid black line, and Heading as a faded gray line
This is useful when there is noticeable current or wind, as you can clearly see the crab angle, which is the difference between where your bow is pointing and where you are actually going
At low speed, the Compass source is always used, regardless of your chosen setting, since GPS course becomes unreliable at these speeds