Dude! Sweet!
Charter Member
Looks like we're going to run P5 next year so I've got to install a GPS in the boat. What do you guys like best and why? Thanks!
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Which GPS unit do you P class guys like best
- Thread starter Dude! Sweet!
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Dude! Sweet!
Charter Member
POPRA doesn't seem to have any similar requirements...
A little off-topic here, but this made me wonder how a situation like this is handled?
My boat can barely touch on 70mph on her best day, yet my garmin shows a max speed of 92mph, something which is a true impossibility. I get this regularly. How would this be handled after a race? Do you guys carry 2 units? Do you examine the data logs?
Thanks.
My boat can barely touch on 70mph on her best day, yet my garmin shows a max speed of 92mph, something which is a true impossibility. I get this regularly. How would this be handled after a race? Do you guys carry 2 units? Do you examine the data logs?
Thanks.
DAREDEVIL
Banned
A little off-topic here, but this made me wonder how a situation like this is handled?
My boat can barely touch on 70mph on her best day, yet my garmin shows a max speed of 92mph, something which is a true impossibility. I get this regularly. How would this be handled after a race? Do you guys carry 2 units? Do you examine the data logs?
Thanks.
If that is the case ,,u would be disqualified. get a new unit or check it .
The unit's fine, it's brand new, and it's not the only one I've ever seen this with. This sort of anomalous occurrence is an unfortunate, yet very real and expected, intrinsic trait of GPS.
A GPS does nothing more than provide a location fix; an X-Y-Z (latitude, longitude, elevation) position. This is the basic measurement, known as a fundamental unit. Speed, heading, course, eta, etc. are all derived, or computed values using your delta position over a given amount of time, usually fractions of a second. Most GPSs provide speed data not as instantaneous readings for every delta, rather they use moving averages over say 5 or 10 discretized movements to compensate for GPSs inherent errors. Remember, most of the GPSs we use are in the range of +/-2 meters with WAAS enabled, but more often +/-5 meters accuracy. This is where we see occasional spikes of troughs in velocity indications. If, for instance, one positional fix is -15 meters, and the next of +15 meters, that's a total error of about 90 feet. This error over say even 250 milliseconds amounts to about 30mph error. All it takes is the gain or loss of a few milliseconds during clock re-sync (because the internal GPS clocks are synced with satellite time at set intervals), or the loss/acquisition of satellites giving slight positional errors, and you'll see some weird indicated speeds.
One more thing: For those with your antennas mounted high, you'll see the effects of rotationally-induced delta velocities in addition (or subtraction) to your translational velocity. When re-entering the water from a launch for example and the boat quickly goes from bow-high to level again, the positive angular velocity will add to your longitudinal velocity. The opposite holds true when rotating backwards.
This can be easily witnessed when sitting idle and bobbing around in some waves...I'll bet your gps is alternately reading between 0 and say 3 mph, just from the swaying.
A GPS does nothing more than provide a location fix; an X-Y-Z (latitude, longitude, elevation) position. This is the basic measurement, known as a fundamental unit. Speed, heading, course, eta, etc. are all derived, or computed values using your delta position over a given amount of time, usually fractions of a second. Most GPSs provide speed data not as instantaneous readings for every delta, rather they use moving averages over say 5 or 10 discretized movements to compensate for GPSs inherent errors. Remember, most of the GPSs we use are in the range of +/-2 meters with WAAS enabled, but more often +/-5 meters accuracy. This is where we see occasional spikes of troughs in velocity indications. If, for instance, one positional fix is -15 meters, and the next of +15 meters, that's a total error of about 90 feet. This error over say even 250 milliseconds amounts to about 30mph error. All it takes is the gain or loss of a few milliseconds during clock re-sync (because the internal GPS clocks are synced with satellite time at set intervals), or the loss/acquisition of satellites giving slight positional errors, and you'll see some weird indicated speeds.
One more thing: For those with your antennas mounted high, you'll see the effects of rotationally-induced delta velocities in addition (or subtraction) to your translational velocity. When re-entering the water from a launch for example and the boat quickly goes from bow-high to level again, the positive angular velocity will add to your longitudinal velocity. The opposite holds true when rotating backwards.
This can be easily witnessed when sitting idle and bobbing around in some waves...I'll bet your gps is alternately reading between 0 and say 3 mph, just from the swaying.
DAREDEVIL
Banned
Ratickle
Founding Member / Super Moderator
You'll have to get one of the main guys to answer this, but every org has contigencies for this. Personally, I like the UMI overseas one the best.
I believe OPA is no more than a 3 second blip. So, even if you actually go over the class 5 speed of 75, as long as it's for less than 3 seconds, you're okay. If for more than that, bye-bye.......
The original question, are you talking about the main GPS unit that is registered to you from the org, or the one (or two) you have in the boat to watch your speed?
I believe OPA is no more than a 3 second blip. So, even if you actually go over the class 5 speed of 75, as long as it's for less than 3 seconds, you're okay. If for more than that, bye-bye.......
The original question, are you talking about the main GPS unit that is registered to you from the org, or the one (or two) you have in the boat to watch your speed?
Dude! Sweet!
Charter Member
I have a 172c now...
POPRA doesn't appear to list an specific GPS model and I wanted to go with something mounted in the dash (rather than on it in a bracket). I wanted something easy to read from a speed standpoint, but also something that has some charting for the Ski Race and the Rum Run (ocean races) and is user friendly.
POPRA rules state the following on breakout:
1. The racers must stay in their bracket speed per lap, if a race boat exceeds the speed in any lap by less than one mile per hour, that team will receive last place points. If a race boat exceeds the top speed of its class by more than one mile per hour, the boat will receive no points and must move up a calss for the rmaineder of the season...
2. The speeds are based on the distance of the actual racecourse. Before the race starts a race official will give scoring a GPS reading of the distance. This is put into the computer along with your time to compute lap speed.
6. Speeds will be confirmed by, GPS, Stopwatch, Radar or any combination of the three.
POPRA doesn't appear to list an specific GPS model and I wanted to go with something mounted in the dash (rather than on it in a bracket). I wanted something easy to read from a speed standpoint, but also something that has some charting for the Ski Race and the Rum Run (ocean races) and is user friendly.
POPRA rules state the following on breakout:
1. The racers must stay in their bracket speed per lap, if a race boat exceeds the speed in any lap by less than one mile per hour, that team will receive last place points. If a race boat exceeds the top speed of its class by more than one mile per hour, the boat will receive no points and must move up a calss for the rmaineder of the season...
2. The speeds are based on the distance of the actual racecourse. Before the race starts a race official will give scoring a GPS reading of the distance. This is put into the computer along with your time to compute lap speed.
6. Speeds will be confirmed by, GPS, Stopwatch, Radar or any combination of the three.
Ratickle
Founding Member / Super Moderator
I just sent POPRA an email. We'll see how they handle it.
Also, your boat will have two GPS's. The official one you are issued by POPRA, and the one (or two) you watch to control your speed.
The official one will be turned in at the end, and reissued before the next race.
Also, your boat will have two GPS's. The official one you are issued by POPRA, and the one (or two) you watch to control your speed.
The official one will be turned in at the end, and reissued before the next race.
Dude! Sweet!
Charter Member
Paul, there is ZERO chance that POPRA will issue GPS units. I'd prefer to let sleeping dogs lie on asking POPRA about this stuff by name. They seem to be very accomodating about getting boats in the water.
I really just wanted to see what eveyone liked to use for race purposes (as your primary I guess...)
Ratickle
Founding Member / Super Moderator
Are you sure????? How else would they calibrate and chart etc. ?????
Dude! Sweet!
Charter Member
If there's only one boat in a race and he breaks out, does anyone care? Wow, I think I'm turning into a buddist!
Sean H
Charter Member
Aren't we in the age of wireless capability and data downloading? Nobody is taking GPS's out of boats and turning them in are they? (I don't really follow the bracket racing that closely, that would just be logical to me.)
Why there isn't some sort of live timing and scoring available with these boats is beyond me. Imagine looking down at your phone for lap times/speeds/scoring during the race.
The F1 app for the iphone is cool. Live timing and scoring and placement on the track.
Dude! Sweet!
Charter Member
Doesn't AMB have GPS transponders now?
Ratickle
Founding Member / Super Moderator
Yes. In OPA, you pick up your unit from Frank, the official break-out guru in the race control trailer, then put it in your boat, then within one hour of the race being over give it back to him for download of info. Otherwise too bad....
I believe they did telemetry testing at a couple of races, including St Clair last year.
(I think I have that right, Dean, Rick, or ?).
Ratickle
Founding Member / Super Moderator
Yes.
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