Technical Controller Survey Techniques

[RLogan]

I don't know how many out there are even interested since this topic concerns TC's primarily. But, as a result of some recent discussions, I am interested in knowing how many TC's out there are using Emmanuel Lion's survey method and Homologation Dossier. And, if not, why not. And how many TC's know it even exists.

[Kelvin]

I've seen it used once, but don't know anything about it.

[thompjs]

I use the Homologation Dossier and it really works nice since I can pull up the previous years tournament and change a few things and done!

 

I don't know anything about his survey,

I've customized the AWSA ones slightly for my ease of use.

[paul]

interesting. I haven't seen it but would like to. I've developed my own survey technique using a theodolite and Solidworks to output the offsets

[RLogan]

Thanks for the responses everyone. That's pretty much what I have heard. Would anyone be more interested if I told you you could plug your Topcon (depending on age) or Leica directly into your computer and have the bearing and distance of each buoy directly placed into the appropriate cell? And, upon completion have a graphic printout of the course with the resulting errors compared to desired positions of the buoys.

 

If so, checkout my PowerPoint presentation on the USA Water Ski website under 3 Event, Technical Controller Resources, Survey Program, Lion Survey Method. Any questions, my phone number is in the Officials Directory.

[Edbrazil]

I have used M. Lion's program. Gets essentially the same results. However, he has a

different set of designations for the buoys, which needs some effort to convert from the

AWSA designations. Which I came up with about 50 years ago, when I wrote the first

computer program for 3-point surveying of slalom courses.

My programs have always used the "best line" through the centers of all 8 main gates. Not

the 55m pregates. Some programs don't do that.

[klindy]

I've looked at the Lion survey program but the issues above made using the AWSA spreadsheet more "user friendly". Plus I've done more 3pt surveys recently than I have 1pt surveys. As I recall the 3pt surveys can't be done with the Lion program. The homologation dossier is fine and that's what I use.

[Edbrazil]

The Lion dossier does have the 3 point option. In the pull-down menu, select "element",

"new element", "classic slalom course". And then select in the "Homologation Mode",

"3 stations". And, format of: min sec degres (sic) or decimal degres (sic).

The program apparently uses the centerline defined by just the endgate centers. Which

can be a problem if one of the endgate buoys is off.

[klindy]

@Edbrazil the AWSA spreadsheet uses the end gates and the pre-gates to establish the best fit centerline.

[thompjs]

@klindy -- I think that is problem too, the pregates have tremendous influence of center line.

[klindy]

@thompjs absolutely correct.

[AWSATechDude]

Guys -- The AWSA Slalom course spreadsheets use all 10 of the pairs of boat guides, including pre-gates and skiers entrance/exit gates and all six pairs of interior gates, to determine the centerline. Prior to the advent of the 55 meter pre-gates, the fit was done based on the 6 interior gates plus entrance/exit gates.

 

When the pre-gates came about in the early 1990's, we initially left them out of the fit, but then frequently found that one or more of those pre-gates were showing up as out of tolerance, in the side-to-side direction. We found that adding them to the centerline fit kept that from happening, but rarely resulted in any of the other 8 gate pairs from going out. So that's why it's done that way.

 

The "Correction Planning" tools built into all of those Slalom spreadsheet templates are extremely helpful in planning and implementing "fixes" for an individually-anchored course which needs straitening up. Check those out.

[RLogan]

To clarify, the Leon method uses a standard surveying technique of a base reference line established between the 4 gate buoys. And, true, if the gate buoys are out of whack it will throw everything else off. But the principle is based on the absolute necessity of gate buoy accuracy. This is easily checked before a survey with a "Check Tie" (Leica term), or "MLM" (Topcon term) of the gate buoys. As far as the numbering convention mentioned by Ed Brazil, Emmanuel chose to use the same even/odd convention of the gates and boat guides to ameliorate confusion, i.e. odd to the right, looking down course, even to the left.

 

True, the Leon sheets allow for a 3 point survey if you want to take the time. I personally feel that the accuracy of EDM Total Stations will result in the same accuracy from a single point. With a reflectorless station, a 25 minute slalom course survey is easily attainable.

[RLogan]

By the way, thanks for all the great feedback!

[thompjs]

@AWSATechDude

It never worked that way for me. They have tremendous influence on the center line.

If doing repairs to bad courses, first remove them.

 

I was seeing this at old sites that had courses installed dry before 55s. If the 55s were dropped in by hand later, it would very often look like the whole course was messed up.

 

 

 

[Edbrazil]

 

I don't use the pregates to define the "best line" centerline. When I started surveying

courses, pregates didn't exist, until about 20 years later. But, the post above is very

interesting. Maybe if the same care is needed surveying them in, but a lot of times they

are somewhat of an afterthought, and not put in with the same care as the other buoys.

The tolerances on them are large, as in almost here and there is OK.

Vs. the new reflectorless laser instruments, they sure can make a survey easy...if the

course is near the single point survey station. Green buoys (pregates) don't tend to give

a good reflection. I might be interested in getting one, but $7,000. or so is way out of

range for me. The guy who does the Miami survey work has become an expert on

working with their reflectorless instrument. I can give you his contact information.

I'm very pleased with my Pentax PX-10D, that I've had for 30 years. A few months ago,

I used a reflectorless instrument, but we had to use a reflector prism, because of the

distance to the course. I found that just entering a desired stakeout distance needed

something like 15 keypresses, making it impractical. With my oldie instrument, it is

very simple to enter a desired distance, so you are reading just errors from ideal, and not

having to do mental arithmetic. I've also found that my oldie still works in poor seeing

conditions, and choppy water, using the "tracking" mode, that reads out to 1cm instead

of 1mm.

Bought the Pentax in 1986 on a payment plan, and it has paid for itself many times over.

[RLogan]

Good input Ed. I was far from prepared to spend $7,000. The Miami guy is my friend Ed Finley who devised his own survey program. I bought a circa 2007 Leica TPS805 Ultra for $3900. Jerry Jackson got religion and found one for $3500 and I've, since, seen them for as cheap as $3200. Make no mistake, a new Leica Flexline will run $8500+, but, really, all you get is Bluetooth and USB capability. You are correct about the color green. whatever that wave length is, it seems to be occasionally problematical. You are also correct in regard to range for reflectorless sights. I'm good out to about 200M. For the majority of my surveys, I set up between 3 and 4 ball. I do not use the pregates for a center line. The Lion program uses the gates. It will perform no calculations until all 4 gate balls are entered. If I'm shooting reflectorless, I will shoot all 4 gate balls first which allows me to see course errors as I do the rest.

[klindy]

I have a Topcon GTS-2B Total Station and it works well. Bought it probably 20 years ago used and except for the batteries it's been flawless. Whenever I use the AWSA spreadsheet templates I enter both the gates and the pre-gates with the same (entrance/exit gate) numbers. Then I analyze the course. After it's all in place I'll reenter the pre-gates and adjust those as needed. I know it reconfigured the centerline but if I know the course is right I can then use the "adjustment" section and ONLY adjust the pre-gates to get everything to work. It may be more steps and take a bit longer but at least I'm sure the course is right.

 

It would be great if there was a toggle to either "use or don't use" the pre-gates for centerline.

 

I've never tried the prismless system but maybe I need to test drive one next time I survey.

[RLogan]

You do not need a reflectorless station to use the Leon survey method. Nor do you have to hook it up to your computer. It merely simplifies the process. You can tell the Leon forms to accept Deg/Min/Sec, Deg/decimal degrees or Gons. if you choose to use Deg/Min/Sec, the entry format for 43°22'51' would be 43.2251.

[klindy]

I get it. I'll try it.