Would GPS Help?

[racingfan1]

When I have asked people in the past why more races are not record races I have been told that one of the biggest problems is the high cost of surveying over water. If I understood correctly , each time a buoy is replaced the course would have to be re-surveyed. Is there any way that placing the buoys by GPS could help? That way you could be sure that the buoys are placed in the same location and eliminate the need for surveying or is it not that easy ?

[diamondprohydro]

It is a little more difficult and still based on the certification of the course by the surveyor. Unless the surveyor is a boat racer, it is a little difficult for him/her to certify that during the record run, the course adhered to the course on record with the Chief Surveyor of APBA, Lee Eason.

I think we would pretty much all agree that at CSH speeds and above, an out of place buoy (either in or out) would probably hinder the speed rather than help. Maybe not on the 1 2/3 mi but most certainly on the rest.

There are some pretty good GPS units out there that are a little more accurate but most still are only good within XX feet unless you use those used for surveying. However the bottom line continues to be the certification of the course.

Hope that helps.

[B Walker]

I have assisted in setting up several record courses. Heres how we did it.

The day before the race a certified surveyor works with us in setting up bouy placement. A white Clorox Bleach container filled with sprayable expanding foam is tied to the bouy anchor line so its about 1 ft below the water surface. In case of a bouy being destroyed, this allows replacement of the bouy without losing the course certification.

At the end of the racing, the surveyor must come back and re-certify the course. This is an APBA rule. You cant use a GPS as its too inaccurate. Consult your rule book for more details.

Heres the problem. These surveyors are not cheap. 500 dollars per survey is not uncommon. Some are more.

Only the largest races are able to absorb an additional cost of 1000 or more for surveying.

BW

[Kev43V]

GPS
There is intentional inaccuracy embedded in your GPS unit. It is capable of much greater accuracy than you are ALLOWED to use.
For instance a gps unit that is registered to a farmer to go on his combine/tractor is good for plus or minus a couple of inches. that data (on yield info) is captured and saved then combined with the data collected by the fertilizer company when they do their soil samples with gps data.
the accuracy they are allowed to use is nearly the accuracy of military equipment. us boat racers are not allowed that kind of accuracy. or any other civilians (except surveyors)
even when we were GPSing a company's pipeline we were not allowed to use the exacting accuracy of the farmers gps. but we were allowed to use better accuracy than the you or I can use personally (same gps unit) just reduced inaccuracy
disclaimer this info is actually kinda old we did the pipeline thing back in 02

[T Chance]

The following is from a Smithsonian Institute web page about GPS:

GPS Accuracy
The accuracy of a position determined with GPS depends on the type of receiver. Most hand-held GPS units have about 10-20 meter accuracy. Other types of receivers use a method called Differential GPS (DGPS) to obtain much higher accuracy. DGPS requires an additional receiver fixed at a known location nearby. Observations made by the stationary receiver are used to correct positions recorded by the roving units, producing an accuracy greater than 1 meter.

When the system was created, timing errors were inserted into GPS transmissions to limit the accuracy of non-military GPS receivers to about 100 meters. This part of GPS operations, called Selective Availability, was eliminated in May 2000.

All images on this page ©1998 Smithsonian Institution.

[Moon child]

Differential GPS

The GPS that most people use are uncorrected. As mentioned by previous posts there is an error that is put into the GPS to keep inaccuracies in the position. This is basically a safety for the government. There are multiple options to correct these inherent errors in position. There are private subscriptions that use demodulator and earth stations that correct the signal. This makes it possible to get what is called Differential Corrections just about anywhere in the world. The US Coast Guard also implemented the Differential Global Positioning Service which was set up for U.S. near coastal waters.

In general the way that the Differential GPS or DGPS works is that the signals from at least 3 of between 24 and 32 satellites in orbit are received by a land based (surveyed) Differential Reference Station as well as your DGPS Receiver. The land station then broadcasts a correction for the difference between the known position of the land based Differential Reference Station and the reported position by triangulation from the orbiting satellites. Your DGPS receiver then applies this correction to the position at your location.

This is a very rough over view but the receivers that rely on US Coast Guard corrections are available and they claim to have accuracy of 3 meters (Usually you will get better accuracy but they cant guarantee it). Not too bad for over the counter. The private satellite subscriptions are much more money but you get what you pay for.

Here is a link with a picture of coverage from the USCG.
http://sc.gpsworld.com/gpssc/data/ar...7/NDGPSmap.JPG

[B Walker]

Think we got off topic a bit.

Copied from the rulebook:

RULE 3 • RECORDS
Records in JR, JH, AXSR, AXSH, SO classes, MO classes, and PRO classes shall be awarded as follows.
1. Competition records of five (5) miles shall be established on surveyed courses laid out in laps measuring one and one quarter (1-1/4), or one and
two thirds (1-2/3) miles and recorded separately. (PRO classes may not set records on a 1-2/3 mile course.)
2. Three (3) mile records shall be established on a 3/4-mile course, 4 laps. The 3/4-mile course will be required to use the layout supplied by APBA
National Headquarters. JR, JH, AXSR, AXSH, SO, MO and PRO classes may also establish competition records of three (3) miles on a surveyed course
of one (1) mile per lap and recorded separately. (As PRO class records transition from 5 lap / 5 mile to 3 lap / 3 mile records, in order to set the initial
3 lap / 3 mile record in each class, the average speed must equal or better the previous 5 lap / 5 mile record speed multiplied by 1.003.)

I dont see anything in there about the survey process. Anyone know where it is? Could a course be set up by GPS and then surveyed for accuracy? If so, I think this would reduce cost to survey a lot.

It took a solid 8+ hour day to set up Lakeland, FL working with a 3 man survey team. But if it were a simple verification of a course set up using a hand help GPS there may be some cost savings.

Something to think about....

BW

[David Weaver]

Permanent Course

I know at Raleigh the inboarders set permanent anchors at the bottom of the lake. There are 1 1/4 mile and 1 2/3 mile courses set. Of course, you need a diver and the surveys of the lake in order to utilize the permanent anchors. And, the inititial set-up takes considerable time and effort.

[bill boyes]

You need a copy of Race Courses and Records booklet by Lee Eason APBA Chief Surveyor. Call APBAHQ and have one sent to you.

[B Walker]

Or its possible it could be added to the APBA website under the Resources tab, Downloads & forms section of the APBA-racing.com website?

If this was done, it would never have to be mailed again.

BW