GPS at FRC Regionals?

[EricH]

I'd rather see 1-2 April Tags on the field. A team who knew what they were doing and the location of the tag(s) could get a pretty good estimate of where they were even if camera(s) on the robot could only see one.

An April Tag looks like a less-detailed QR code. I understand that by looking at size and angles of the lines in it, angle and distance can both be calculated.

[BBray_T1296]

Originally Posted by EricH

I'd rather see 1-2 April Tags on the field. A team who knew what they were doing and the location of the tag(s) could get a pretty good estimate of where they were even if camera(s) on the robot could only see one.

That is something we did with our vision targeting code in 2012. By knowing the exact size of the backboard, we could determine our distance (based on pixel counts) and had a system for interpreting trapezoids (ie: at an angle)

[seg9585]

Dead reckoning and double integration from accelerometers produce a large amount of error even during a 2-minute FRC round.
I like the idea of embedded RFID -- maybe they could be hidden in a grid configuration below the carpeting, and a sensor on the robot could update its position as it moves over the RFID.

By setting up multiple repeaters in an atneea you can derive your own geolocation, although at that point you may as well design your own field-relative system. I'm guessing you can get pretty accurate results by placing transmitters on the field boundaries.
You could possibly even accomplish it with a sonar-based transmission system -- derive relative position with respect to certain sound frequencies, all transmitted simultaneously from 4 corners of the field.

[wireties]

GPS is a line-of-sight technology. It pretty much does not work indoors.
Commercial GPS receivers do not give us the resolution necessary for FRC.
Differential GPS (like that provided by the Coast Guard for coastal navigation) is much better (maybe a few feet) but stiii not good enough for FRC. But some other radio-based navigation element would be cool in autonomous mode, perhaps a simple directional beacon of some sort?

[Al Skierkiewicz]

GPS has been tested by several teams in several venues with disappointing results. Many modern venues have too much steel in the roof deck to get a good GPS lock.

[seg9585]

Originally Posted by wireties

GPS is a line-of-sight technology. It pretty much does not work indoors.
Commercial GPS receivers do not give us the resolution necessary for FRC.
Differential GPS (like that provided by the Coast Guard for coastal navigation) is much better (maybe a few feet) but stiii not good enough for FRC. But some other radio-based navigation element would be cool in autonomous mode, perhaps a simple directional beacon of some sort?

GPS has been tested by several teams in several venues with disappointing results. Many modern venues have too much steel in the roof deck to get a good GPS lock.

As I described, adding multiple repeaters on the roof of the venue and re-transmitting the GPS signals indoors would resolve the indoor tracking issues. Differential GPS can provide inches, not feet of precision -- which is plenty of resolution for the FRC field.

Here's a quick article/caption that mentions the concept:
http://www.engadget.com/2007/02/21/u...your-position/

Apart from this, creating a local positioning system environment as described in this thread may be feasible using an RF based system (rather than attempting to detect field objects visually, which in my experience has been quite error prone due to unknown and varying field lighting conditions)

[Joe Ross]

Originally Posted by seg9585

Here's a quick article/caption that mentions the concept:
http://www.engadget.com/2007/02/21/u...your-position/

It's not nearly that easy. See this article for a description of the problem and one possible solution: http://www.insidegnss.com/node/1581

[lynca]

Originally Posted by EricH

I'd rather see 1-2 April Tags on the field. A team who knew what they were doing and the location of the tag(s) could get a pretty good estimate of where they were even if camera(s) on the robot could only see one.

Absolutely agree, I used April tags quite a bit to track robots and it was an excellent way to get position and orientation.

[Michael Hill]

I can't think of a reason why having April tags you put up at your driver's station window (think poster board size) would be against any rules. If you tell your robot which driver station you're at, you should be able to see it. Just hope your drivers can see!

[Nate Laverdure]

Originally Posted by Michael Hill

I can't think of a reason why having April tags you put up at your driver's station window (think poster board size) would be against any rules. If you tell your robot which driver station you're at, you should be able to see it. Just hope your drivers can see!

See T22.E.i and ii

[EricH]

Originally Posted by Nate Laverdure

See T22.E.i and ii

Just so we're all aware of the full relevant text of the referenced rule...

T22
The only equipment, provided it does not jam or interfere with the remote sensing capabilities of another Team, including vision systems, acoustic range finders, sonars, infrared proximity detectors, etc. (e.g. including imagery that, to a reasonably astute observer, mimics the VISION TARGET), that may be brought in to the ALLIANCE STATION are as follows:

A. the OPERATOR CONSOLE,
B. non-powered signaling devices,

E. devices used solely for the purpose of planning or tracking strategy provided they meet all of the following conditions:
i. do not connect or attach to the OPERATOR CONSOLE
ii. do not connect or attach to the FIELD or ARENA
iii. do not connect or attach to another ALLIANCE member
iv. do not communicate with anything or anyone outside of the ARENA.

Mr. Lavedure is using the April Tag as a device "used solely for the purpose of planning or tracking strategy". However, doing so completely misrepresents its real use: as a sensor target. It's not for tracking strategy at all!

As a sensor target, it should be classed as a non-powered signaling device (it is signaling a location, to any robot that happens to see it and be able to read it), and thus be subject to T22-B, rather than T22-E. T22-B passes it in as equipment that may be brought into the Driver's Station.

As it is attached to the Operator Console, and could theoretically be small enough to be the back pattern of the laptop, it could also theoretically be counted as part of the Operator Console... but that's unnecessary as it's already in.

This assumes that no April Tags exist in the field itself; should there be one or more, T22 takes over and kicks it out under mimicking part of the field.

[Nate Laverdure]

Originally Posted by EricH

It's not for tracking strategy at all!

Good point Mr. Husmann; I retract my comment