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GPS Accuracy Question....

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brentonw2004

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Hello again everyone! This may be a crazy idea, but I guess that is what eventually brings better technology. I want to build a robotic lawn mower. I plan to modify a normal gasoline mower and drive it with electric motors on the rear wheels. I know I could make it to where I could control it by remote control, or maybe even with wires in the ground to mark the bounderies and have it do its job autonomously. But this is not exactly the way I would like to control it, and I know that these ideas are not new either. What I would like to do is equip the mower with GPS. I would like to build the GPS module into a circuit that I could remove and attach to either a laptop/palm pilot and interface it by either USB/rs232 so that I could basically walk about the lawn and mark off my bounderies by uploading the GPS positions into the software I would run it off of, then I would reattach the GPS to the mower and upload the map data to the mower. My idea is to basically use a computer of some type that is attached to GPS and let the software generate a virtual map that the robotic mower could wander about inside its bounderies according to an algorith to keep it's path neat. I am fairly confident that I could get the software and the elctronics of this project to work. Does my idea sound plausable? Any suggestions. I would like to attempt this, but my main question is, what is the most accurate gps that I can get? I have read up on some of them, and 3meters is about the most accurate I could find. That could possibly work for large fields, but I would neat much more accurate for something that could work on small lawns. Is it possible to get a gps that would work within 1ft? Also, how often do most GPS systems refresh? I believe that my design would need a refresh rate of at least 2 times a second. Any help would be appreciated. I know that this idea is rather advanced, maybe even ahead of GPS technology, but it is only an idea. If GPS is impossible to use, how else could I get a computer generated map for the mower to rome in. Thanks for reading and I look forward to suggestions.
-Brent
 
I don't think you will get GPS anywhere near accurate enough. I would have said 3ft is a bit of an exageration, even if using military equipment.

I wonder if you could use a slightly different method. Put a transponder of some sort on the mower (or you when you want to walk out the boundries), and several direction finders around the garden. The computer could take the signal from the direction finders, triangulate it, and work out the position.

Possibly this wouldn't be accurate enough either, but its just something else for you to consider.

Tim
 
i wud use transmitters at various points so it knows were it is. GPS isint accurate enough for that kinda thing (yet)
 
Does anyone know what the most accurate GPS is? Best brand? Even with a lower resolution and my idea, you could use it on larger tracks of land with less complicated boundaries, just nothing too small or complicated... What would it take to build a better GPS? How accurate do you think I could get by using a couple permanent transmitters and calculating out the triangles? Any suggestions for a starting point on this? Also, this may be a little more vulnerable to error such as tire spin etc., but I could imagine using an accelorometer on the map generating device to just calculate the speed & direction and make the map that way, then have the mower count it's tire revolutions to know where its at. Either idea would be a lot more complicated than GPS, but who knows when GPS will get a high enough resolution... Thanks guys! All help is greatly appreciated!!
-Brent
 
A fellow engineer and wannabe farmer described what he understood of a current application of GPS to agriculture and the level of accuracy is similar to your requirements. I was left with the understanding that a planter, excavator or similar piece of equipment was controlled by an on-board GPS unit that periodically referenced a nearby landmark - a large rock, tree or similar monument - to provide error correction. I also understand that surveyors use GPS technology to a high degree and would guess that they employ similar methods. You might do a google search under agriculture and GPS to see what turns up.
 
3ft...pfft, if you pulled it off you would be rich. Miltary standards dont even meet this as said earlier. Seeing GPS works on timing differences and that radio signals travel 3mm in a picosecond, 3 feet which is about 1000 millimetres = 333picosecosnds, you would need to be able to transmit information at the rate of about 3Ghz !!

A better idea would be to convert it into a remote control version where you control it manually, just without the nescessary manpower.
 
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