Outdoor tracking

Yes i known that i can carry the bag, i can also walk to work and walk to the TV to change the channels! This is not a project i want to do because i am lazy (cough: i guess i am, but innovation is made by lazy people!)
This is a project i want to do because it is fun and challenging -> everybody can make a led blink........
And it has been done: GoGo "follow me" golf trolley. http.//www.omgsrl.it - YouTube

Problems with different sensors:
IR -> can be disturbed by the sun
Maybe some kind op blinking IR transmitter and the receiver should detect that "code" - and the direction could be 2 (or more) receivers separated by a plate parallel to the straight forward direction -> so that if the left receiver sees the signal, but not the right one the bag has to go left!
But my "worry" is that the IR receiver cant see the blinking IR transmitter, but only "sees" the sun!

ultra sound -> maybe not so good in rain and wind !

Gps -> expensive! and is it accurate enough? i meen what is best case 2,5 meters ?

But my "worry" is that the IR receiver cant see the blinking IR transmitter, but only "sees" the sun!

By blinking do you mean modulated?

The ides is that the amplifier of the incoming IR signal is tuned and only amplifies the modulation. Of course that doesn't help you if the receiving sensor is saturated.

Gps -> expensive

Yes

i meen what is best case 2,5 meters ?

No much more accurate than that. You can get accuracy down to about 1cm. Then you trade off price for accuracy.

Hehe!

Yes! accuracy can be under 1 cm (with a price of 20k$)

In everyday GPS handheld units its about 4-6 meters!

(with a price of 20k$)

Being ripped off here, don't need to spend more than $3k

In everyday GPS handheld units its about 4-6 meters

Yes but you want relative accuracy not absolute accuracy in your application.

So they are 4-6 meters out in the absolute coordinate system, but more precise relative -> that was new to me!

How precise are the cheap gps units relatively?

And can you recomende one?
Remember i need 2 if i am going for that solution, so cheaper is better :wink:

So when i said that a GPS isen´t accurate enough it wasn´t untrue!

Hmmmmm! There must be some kind of "sensor" that can do the job!

You need to notify the general area that you have an autonomous golf bag with a mind of it's own... maybe you need to have it wear a T-SHIRT when it moves on its own.

Like maybe this:

The major causes of error in a GPS system is the difference in propagation through atmospheric cells. WSS compensates for this locally. I would disagree with what Richard said

A small child could do it

OTOH, an autonomous machine is unlikely to get bored and start hitting its sibling with the contents of said golf-bag

LIDAR

I would love to see a practical, real-world example.

Well, WAAS has already been mentioned.

Differential GPS does the same thing, on a smaller scale. It uses a fixed station at a known point which calculates errors and send them to the mobile unit for corrections.

An obvious example would be one of those spiffy military GPS units, like those used on JDAMs, cruise missiles, etc, that use the second (still encrypted) GPS frequency that's far enough away from the ~1.5Gz signal we mere mortals use that the atmospheric distortion can be compensated for onboard.

-j

http://cgi.ebay.com/Arduino-GPS-Netduino-GPS-receiver-w-tutorial-Sparkfun-/250686123796?pt=GPS_Devices&hash=item3a5e0eaf14#ht_499wt_1048

Get two of these and xbee's, you can easily have your cart follow you.

So you think that theese gps units are precise enough relatively??

What is the purpose of the xbees?

Ok i wasn't totally awake when i wrote this.
I was still focused on "ir tracking" but using gps the cart off course need to know where i am :wink:
This is an expensive solution, i need to know if it is stable enough.

Perfect. All Mr. Pulse has to do is increase his GPS budget by 20x

I'm not sure of the cost of a DGPS rig. I'm sure comercial is expensive because of its applications, but I don't know if one can be homebrewed.

and then have his robot and the target both stand stock-still while they make a precision fix.

Wrong.

-j

A cheap and quick solution:

A thin rope attached to you, and to a joystick on your bag.
When you move it will pull the joystick on your direction and then let know to the Arduino where to go.

Another way could be a 360° coverage based on ultrasonic long range sensors + a button to start and stop the stracking (and avoid your bag to follow a rabbit crossing arround)

Hi all

I was on an electronics exhibition yesterday and got an explanation on how it works!
Before the explanations I was not totally aware of the difference between absolute precision and relative precision!
Well! Error correction, by having a fixed reference point, works because the same error is shown in both devisees and therefore you can correct the data on the moving device. Because the same error shows up un both devices, then there is no need for error correction, because gps1 has to follow gps2.
So the absolute precision is "gps to satellite"
and relative precision is "gps to gps"

So if i bought 2 gps units that can have a DGPS corrected precision of 1 cm, then the "golf bag" would follow me around with a precision of 1 cm.

But it is still expencive!
For this solution i need 2 arduinos, xbee tx/rx and 2 GPS units!

And for an ir solution (if it is possible) i only need 1 arduino and some ir tx/rx

1cm precision can't be reached for civil GPS devices. 10m will be the best you can have.
So your bag should be somewhere 20m away from you, and it will be funny to see you trying to catch it when it's thinking you'r always 10 or 20 m away... ;D

@razorbob:I've seen civilian-grade GPS antennas attached to opposite ends of bulldozer blades for precision grading. Do you think that would work if they were only accurate to 10 metres?

@razorbob

You are right about absolute positioning to the world coordinates!

But the thing in this case is that 1 GPS unit is telling another GPS unit where to go!

So in theory if there is som kind of atmospherical distubance that makes GPS1 jump 5 meters in a bearing of 200 degrees, then the same error would show up un GPS2, so that the relative position between the 2 GPSs are the same!

Differential GPS (DGPS) works by having a GPS unit at a known position (lets say 100,100) but this GPS reports 101, 98) -> then this error (1,2) is sendt to the moving GPS unit out in the field by gprs (or other way) and applied to the GPS unit as correction data!

This can ONLY work because the 2 GPS unit sees the same (absolute) error!

Remember, i don´t have to know where i am in the world, i "only" a relativ position between 2 gps units that are acting on the same data!
So the important data to look for in the GPS unit is not the "absolute" value, but the DGPS precition -> because this value is showing how precise the GPS is itself!