I've been thinking of what heading sensor to get for my boat. I like the idea of a GPS compass, but the ones in the market right now are out of my price range.
In my mind, a GPS compass should not be that complex. It seems like all that is needed are two or more antennas set at a known distance from each other, a processor (laptop, PC, etc), and a software program that turns the position information from the antennas into heading information. Am I over simplifying this? Has anybody done this before? If it hasn't been done, it sure seems like an opportunity for a savvy programmer.
Hi Norton Rider, There was recent discussion about this on an entry about the SeaPilot compact (and fairly inexpensive) sat compass:
https://www.panbo.com/archives/2014/11/seapilot_vector_compact_gps_compass_true_heading_comes_to_the_usa.html
In short, I don't think a homemade GPS compass is as easy as it might sound.
But I'm wondering if you really need one. What's the purpose and don't I recall that you're updating MFDs on a budget?
Hi Ben,
You are correct in that I'm updating on a budget and will probably end up buying a lower-end heading sensor.
Having said that, I've always been intrigued by GPS heading sensors and wondered how one could be constructed. I guess the question is, how reliable the data would be from a homemade one that only depended on GPS antennas and did not have rate sensors, etc. It seems like the basic algorithms necessary to provide heading from two GPS antennas should be relatively easy to program.
"...relatively easy to program"
There's the thing; GPS compasses do NOT simply compare the positions of different receivers to calculate heading. It's a LOT more complicated than that:
http://www.cactusnav.com/newsdesk_info.php?newsPath=17&newsdesk_id=16
If you're getting a heading sensor mainly to do radar overlay, have you considered just using COG?
Ben,
You are correct. It looks like the GPS compases use Carrier Phase GPS. I did some searching and found a good explanation of this in the Trimble website: http://www.trimble.com/gps_tutorial/sub_phases.aspx.