That is quite annoying when you for example want to have a marker dynamically change its angle to mark a unit's faced direction on the map...
Well, you can use two markers: one is always right on the player, while the second is a little distance away from that marker, in the direction the player is facing. Think of a circle, with a dot that revolves around it to match the player's facing.
I tried this in my combat patrol mission, but I decided (a) it didn't look too good (especially when you zoom in or out a lot), and (b) the player gets a compass anyway, which is more realistic to use anyway.
But if you really wanted to show facing with markers (for AI units or other player, perhaps?), then you could try that method.
Ex:
"dirMarker" setmarkerpos [(getpos dude select 0) + 5*(sin getdir dude), (getpos dude select 0) + 5*(cos getdir dude)]