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GPS guidance

Old 05-05-2006, 08:13 PM
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lvspark
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Default RE: GPS guidance

It might, but you won't see me standing anywhere near-by!
Old 05-07-2006, 02:25 PM
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Default RE: GPS guidance

Can I use my Garmin etrex with the new RCAP2?

Jack
Old 05-07-2006, 02:40 PM
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Default RE: GPS guidance

ORIGINAL: vortex00

Can I use my Garmin etrex with the new RCAP2?

Jack
Yes,

Go into the "Setup" menu then "Interface" menu option. If not already done, select NMEA out in the I/O format. Garmin units come defaulted to Garmin I/O. It's an easy swap. Then just use an eTrex serial to DB9 cable to connect up to your RCAP unit. You can also custom make smaller lighter cables. I recommend powering the eTrex from an auxilliary regulated power source. This keeps it operating in the air much better. The Garmin units in my assessment and experience can shut themselves off under vibration conditions. This might be due to battery compartment connections. I never have experienced a shut down with my geko while powering it externally. Here's a thread on a hack that may or may not do you any good. It's a lot cheaper than a factory OEM cable and is very secure if done properly. The little connector Garmin uses on the back of the eTrex has to be handled pretty carefully to stow in flight. You don't want that little thing popping off or your guidance is gone in a heartbeat. http://www.rcapa.net/forums/viewtopic.php?t=503

Dan
Old 05-07-2006, 03:42 PM
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Default RE: GPS guidance

Dan,
Thanks for the good info and start into the UAV world. Excellent link.

Jack
Old 05-08-2006, 12:42 PM
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wsmalley
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Default RE: GPS guidance

What's the least expensive GPS today for flying waypoints? I have an old Garmin 12 which is too heavy. I have an original PDC 10 and an overlay from BlackBox in the UK. Was thinking of getting the eTrex-the first yellow one. It appears the WAAS data is not sufficient for altitude purposes at our scale. I read somewhere the 'automatic landing systems' on some full scale A/C uses 2 units with DGPS. I thought WAAS was supposed to be extremely accurate? Maybe the guys in black suits are varying the data.
Old 05-08-2006, 02:35 PM
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Default RE: GPS guidance

A lot of us are using the Garmin geko 201. It's pretty small and pretty adaptable to our use. I always try to tell people it's best, especially with wet fuel planes, to use auxilliary or external regulated power to the GPS. There have been reported and I have seen the GPS shut off in flight if you only use internal batteries. The battery holder in the back case of the unit just has two tabs holding power to teh circuit board so I suspect this is the problem. There is also a tiny battery inside that I've had vibrate loose and cause me to have the GPS shut down. There's a link to a modification and cabling that makes the unit more UAV freindly that I can post later. It's on the RCAPA forum site but they have me blocked from my work e-mail address so I can't recover the link for you.

Dan
Old 05-08-2006, 07:40 PM
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Default RE: GPS guidance

Here's the link.

http://www.rcapa.net/forums/viewtopic.php?t=503
Old 05-10-2006, 05:03 PM
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Default RE: GPS guidance

Thanks for the info and the link. The hack looks pretty simple. Does the 'geko' have features that the basic eTrex doesn't have? I guess, that is, features beneficial to UAV use. Bill S.
Old 05-10-2006, 09:55 PM
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Default RE: GPS guidance

They have pretty much the same features and software. Newer units have WAAS enabling which gets it a little more accurate. Either one will do you. The geko is a little smaller than the eTrex. I prefer my eTrex for back country use over the geko. But the geko over the eTrex in the plane just for size. Also, depending on how you mount it, the eTrex has buttons on the side and can be hard to access. The geko has them on the front panel. The geko buttons are easy to get to if the mount wraps around the case. It's really just DC. (Designers Choice)

Dan
Old 05-11-2006, 10:01 AM
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Default RE: GPS guidance

Good info! Question that comes to mind, though, is plotting waypoints in advance of a flight. That is, how? It seems the points have to be greater between them than the time it takes for the GPS to refresh. Then, does one normally walk, or drive, the anticipated route to set the wp's, or can you plot them off a map accurately enough? And, finally, can the GPS become confused as to which wp it's trying to acquire-seem to remember reading that somewhere long ago? Bill
Old 05-11-2006, 04:22 PM
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Default RE: GPS guidance

ORIGINAL: wsmalley
Then, does one normally walk, or drive, the anticipated route to set the wp's, or can you plot them off a map accurately enough? And, finally, can the GPS become confused as to which wp it's trying to acquire-seem to remember reading that somewhere long ago?
Bill,
Usually when I setup my routes I do it in TopoFusion and Expert GPS. These are programs that allow me to edit waypoints and routes. After I'm done editing my route I upload it to my GPS. If you have 'urban' satellite image coverage you can get some pretty accurate routes built. I've attached 3 jpg's to give you an idea of some routes I might fly....
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Old 05-11-2006, 04:38 PM
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wsmalley
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Default RE: GPS guidance

Cool! I presume these are commercial software programs-expensive? Can your 'finish' point be at, or slightly past, your start point. My question being, basically, can you program your plane to literally fly down the runway? Sort of an automatic landing system.
Old 05-11-2006, 07:35 PM
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Default RE: GPS guidance

ORIGINAL: wsmalley
Cool! I presume these are commercial software programs-expensive? Can your 'finish' point be at, or slightly past, your start point. My question being, basically, can you program your plane to literally fly down the runway? Sort of an automatic landing system.
I think they cost like $30-$40 each. It's some software that I've been accustom to. There is other GPS software out there, it's just a matter of what you want to do with it.

As far as autoland this is something that has not been focused on by modelers just yet. There are some complications with it. I've been tempted to give it a try, just haven't had the time yet. Garmin's GPS's have something called Smart Route in them. This sometimes messes up your route. This is also why I put Start and Waypoint 1 very close together. When you start a route it automatically skips past 'start' and starts navigating to WPT1. If you put your Ending waypoints to close to the start it will skip over everything else and go right to the end.

If I was going to land with just a RCAP and a FMA CoPilot I'd have to set my route to overshoot the landing zone. In reality I'd still be landing at WPT10.. The Overshoot is so the RCAP doesn't hit the last waypoint and start circling. I'd still have to manage the throttle myself. The FMA CoPilot would then keep everything level. Then the RCAP would just stear the route. I'd still have to flare at the very end. If you look at the attached WPT6 to the end would be me attempting to keep the RCAP on a straight line.
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Old 05-11-2006, 09:40 PM
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Default RE: GPS guidance

Here's a thread thats worth reading at this time. It explains how steering devices control the rudder and farther on, how "smart route finding" gets in the way of what we're doing and how to get around it.

http://www.rcgroups.com/forums/showthread.php?t=475531

Dan
Old 05-11-2006, 10:42 PM
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Default RE: GPS guidance

I realize the limitation of the GPS as far as the altitude is concerned. The idea of an ALS has interested me for some time, why, just 'cause it would be fun to do. There must be several ways to accomplish it. The waypoint could take care of the lineup for the approach, throttle doing the altitude, and as you say, an autopilot to keep it level. I have the FMA Co-pilot, and fly a couple of PA1's. The main reason I'm just starting is not having a plane large enough to carry all the gear.
Old 05-12-2006, 12:16 AM
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Default RE: GPS guidance

One way I was thinking was to have the autopilot line the thing up. At a certain waypoint the autopilot does like a -15/20 degree decent based off of the barometric sensor. At the same time another sensor detects your airspeed to keep the aircraft from stalling. After the craft reaches say 5 feet off the ground to me it'd seem like you'd want to switch from barometric to ultrasonic. Perhaps you'd want to do a compairison between the ultrasonics and the barometric sensors. Hopefully by this time you'd be somewhere near a clearing for the runway. When your down to the last 2 feet of the run you could almost just 'dump' the throttle and let the sensors do the rest. Sadly I need to find some time in my schedule to learn some programming. Then maybe I could quit talking and start making

I know there is all this stuff about flairing at the end. Usually when I come in now I'm actually holding a certain amount of up elevator on my decent. I then use the throttle as my altitude control all the way end. I don't know if it's just the difference between pushers vs tractors or what.
Old 05-12-2006, 07:59 AM
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Default RE: GPS guidance

I have thought the same thing as to the ultrasonic idea. To that end I bought an old Poloroid with the idea of hacking the board-there are/were some sites to do that. I also bought a garage gizmo that works off ultra sound and triggers a green, yellow, and red light as you get to about 2' from a wall. I have a BTA 06 autopilot, and an older gyro which I thought if you could line up on the approach and engage, would keep you on the approach. The problem, I think, with the barometer is that it's more of a 'hold' device. I don't understand how you could program a descent. Maybe with the new baro sensors, and some neat programming, you could 'hand off' between several sensors set at varying altitudes. It's been done! There was a neat site of the F-16 twin turbine project that North Carolina State (?)did-it ultimately crashed. The Predator has I think an ALS system. The first one was done in 1937 with a Fokker and 'State of the Art' 1937 radio gear.
Old 05-18-2006, 01:04 PM
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Default RE: GPS guidance

Interesting stuff...a long way off for a newbie like me, but interesting nonetheless.

"laser" tape measures typically use ultrasonic sensors, can you hack in to one of those to get some altititude feedback?
Old 05-18-2006, 05:28 PM
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Default RE: GPS guidance

I don't think being a 'newbie' has anything to do with it. I expect a good electronics engineer, who happened to fly RC, could design something pretty easily. I looked at the laser measuring devices, seems they are limited pretty much to 50'. I'm confident there are several ways to go about this, partly, I think one has to just decide on some parameters and then work toward them. I don't have a lot of hours, but, I've flown high wings, low wings, a U/L, and a Schweizer sailplane and they have similarities, for example, you have one altitude you seek to attain when you are on your downwind leg. We all pretty much know where our models are when we turn base but, I don't have a clue what the actual altitude is for mine. I'd guess +/- 100'. It would be desirable to make a long, straight in approach, but I rarely see anyone do it with a model. Guys with gps/overlay experience know what the 'target' altitude is when they hit their last waypoint. My point is, a linear approach may be better, but I think a stepped approach might be easier to program. I think you need some kind of 'artificial horizon' -like the numbers on the runway- to aim for that would trigger the light, or heat sensors-kind of like what the FMA copilot reads. Anyway, it's a fun exercise.
Old 05-18-2006, 05:30 PM
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Default RE: GPS guidance

I don't think being a 'newbie' has anything to do with it. I expect a good electronics engineer, who happened to fly RC, could design something pretty easily. I looked at the laser measuring devices, seems they are limited pretty much to 50'. I'm confident there are several ways to go about this, partly, I think one has to just decide on some parameters and then work toward them. I don't have a lot of hours, but, I've flown high wings, low wings, a U/L, and a Schweizer sailplane and they have similarities, for example, you have one altitude you seek to attain when you are on your downwind leg. We all pretty much know where our models are when we turn base but, I don't have a clue what the actual altitude is for mine. I'd guess +/- 100'. It would be desirable to make a long, straight in approach, but I rarely see anyone do it with a model. Guys with gps/overlay experience know what the 'target' altitude is when they hit their last waypoint. My point is, a linear approach may be better, but I think a stepped approach might be easier to program. I think you need some kind of 'artificial horizon' -like the numbers on the runway- to aim for that would trigger the light, or heat sensors-kind of like what the FMA copilot reads. Anyway, it's a fun exercise.
Old 05-19-2006, 05:53 PM
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Default RE: GPS guidance

This may do the trick in determining distance if you know how to program a PIC microcontroller.

http://www.hobbyengineering.com/H1053.html
Old 05-20-2006, 06:22 PM
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Default RE: GPS guidance

Thanks for the tip! I had seen that site but, missed that circuit. I had about decided the ultrasonic method was the logical choice for left and right control but not sure if you could control up and down. Assuming you had a sensor giving you a range to the ground, you still need a 'range' to something up for elevator control. There are some robotic circuits that would track distance and move left or right but a glide slope seems more problematic. I think part of the problem is the size of an RC plane. The distance from top-say of rudder- and bottom of fuse is so small. The big jets that have tried ALS have used DGPS mounted topside and bottom, or so I've read. Don't know how the Predator, and others do it. does it.
Old 06-05-2006, 05:31 AM
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imam sugalih
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Default RE: GPS guidance

hi, I am from indonesia.

I am just a month using an RC helicopter.
I want to be able to fly helicopeter as fast as posible. I don't want to get crash when learning RC helicopter.

Is the GPS guidance usefull for me for hovering and to keep my helicopter at position when slightly windy.
Old 06-05-2006, 11:33 PM
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Default RE: GPS guidance

I have begun to wonder about what dangers we pose to full size aircraft (not to mention people and property on the ground) as we use the latest in technology to allow a model to travel out of sight and out of our manual control range. It seems very dangerous since we may be operating totally out of range for live video transmission back to the pilot (one account recently covered a flight of 2.5 miles). It is very likely we have no means of avoiding a collision with a helo (or any low flying aircraft ) attending to a news story, law enforcement or an emergency when it intersects with our model's flight path.

How can we defend our actions should the first accident occur? How can we keep the FAA from severely limiting the hobby for everyone? I doubt the agency will consider whether we are involved in an experimental aerial photography extension of our hobby or we are just ordinary Sunday sport fliers at our individual fields? Of course, no thinking R/C pilot would allow a model to come near the airspace of a full sized aircraft, but what if you couldn't see the possibility looming? I am very interested in seeing any discussion on the subject.

Brad
Old 06-07-2006, 03:04 AM
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Default RE: GPS guidance

Great post brad.... Go somewhere else and spread your dribble..

On second thought, don't go anywhere.. Stay in your house cause the sky is falling and over 40,000 people die in car accidents every year.

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