Jump to content
Sign in to follow this  
laserbounce

DGPS Auto-Landing System

Recommended Posts

Okay, I've been reading up on gps technology and am wondering if anyone has used DGPS (differental global positioning satellite system) in a model aircraft or even a land craft! DGPS is supposed to be accurate to a few centimeters by subtracting the coordinates of a gps unit at a known location to an gps unit at an unknown location nearby. The commercial jets have an automatic landing system that uses some kind of DGPS.

If I put one gps in my plane with a Tiny-Trak like device and one gps plugged to my laptop at the edge of the runway and write software to control my radio transmitter through a trainer cord and the laptop is programmed to know where the plane should be at each point during final approach, do you think it would be accurate enough to safely land the plane? Any thoughts welcome.

John

Share this post


Link to post
Share on other sites

I use to have DGPS on my boat . And I didn't get anything that accurate.

It claimed to be accurate to about 15' or so.

Take a look at:

http://www.westmarine.com/webapp/wcs/store...dvisor=waas.htm

You will get some details/history on GPS.

I never looked into size, but my DGPS antenna was quite large and heavy.

About the size of a large grapefruit with a 10" antenna or so on it. It was made for the marine environment weight etc. was not an issue.

I was actully quite mad, since about 1 month after I put the system in, Clinton removed the scrambling from GPS signals which made GPS just as effective as DGPS.

Personally I was thinking of having some LED's on either side of the runway and some kind of sensors that would keep the plane between them.

A sonar could be used for low level altitude readings.

Just some thoughts.

Share this post


Link to post
Share on other sites

I think you need a bit more than accurate GPS to ensure a reliably safe landing. I believe you will need additional stabilization on most models to keep them level & stable during the approach. It does not need to be closed loop with the Tx's software, via telemetry, but that would be cool if it was. The FMA CoPilot system might provide a ready solution.

Share this post


Link to post
Share on other sites

I have landed a Tower Hobbies Trainer 40 by WAAS GPS and FMA Co-pilot. I set up a waypoint well past the landing strip in the GPS before takeoff, then when I got ready to land, I turned up the gain on the Copilot to full gain, activated the PDC-10, backed the throttle to idle and stood by and watched, the hard part was standing by and watching :D

Share this post


Link to post
Share on other sites

Yes, I do agree the FMA co-pilot would probably be necessary to stabilize the craft.

KE4UVQ, how accurate is your WAAS? And how wide a runway could you land on? My gps receivers seem to drift quite a few meters.

I am considering ordering some high quality gps receiver boards like the Motorola OnCore that produces pseudo range output data streams, as the professional surveying systems have the accuracy, but are way to expensive. When using two receivers you may get data from different satellites and ionosphere propogation can result in several meters of measurement error in the calculations.

I read an interesting website today of a university project where they tried to build a robot to automatically walk on sidewalks using a magellan dgps beacon receiver, and sure enough it wasn't accurate enough to drive down anything short of a double lane road.

It appears we need to be able to compare the same satellite signals against each other over a small geographic area to get consistent runway accuracy in the one meter range.

John

Share this post


Link to post
Share on other sites

The accuracy of WAAS wasnt a factor in the altitude during landing, a high wing trainer will basically land itself if you line it up at the end of the runway for an approach and pull the idle back, itll settle in and land unless theres a cross wind, then you make corrections manually, but the copilot keeps the plane level, the GPS/PDC 10 keeps the plane pointed at the waypoint, the plane comes in and lands. WAAS is a help with the accuracy of where the plane is currently located. Im getting about 7 meters on average with the WAAS DGPS signals being received on my Garmin GEKO 301. WAAS is great, it takes the trouble of DGPS separate receiver and DGPS antenna right out of the equation.

So unless you are after a TRUE Autolanding system, this setup will put the plane on the ground with little input from the pilot, pulling the throttle back and activating the Co-pilot and PDC-10/GPS.

Share this post


Link to post
Share on other sites

Aw man, I just realized who Im talking to. Laserbounce if your still in town this weekend, Ill be at the Flying Gators field on Saturday, Ill show you my setup!

The FGMAC field in Archer is the one Ive tested this on.

Ill PM you with my number!

Share this post


Link to post
Share on other sites

Mike, do you have the geko hidden away in the airplane or does the antenna have a clear shot of the sky?? I know being under trees really changes my altitude when I am walking around, thought balsa might change signal enough to throw altitude reading off.

My next project is auto tracking antenna for video and finishing my new text overlay.

Matt

Share this post


Link to post
Share on other sites

This is the Orange and Black UAV that Dave and I were test flying when I was down there last, I dont think you saw inside. Its under the rear of the wing facing up. But as I was telling LB, it doesnt need altitude to land the way I tested.

(We dont need no stinkin altitude) :P

Matt are you back from IL yet?

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×