Measuring a course

[gameboy9]

Have a question about measuring a course. As some may know, Codorus is missing some measurements from tee to hole... I'd like to fill in the gaps within the next month or so... I don't think Codorus's web site will help me here.

The question is... how is the best way to go about doing that? Surely I have to use a measuring wheel, which isn't much of a problem to get... get a small 4" diameter measuring wheel, that should be fine. I'm guessing I should start from the end of the tee box (if there is one) to the pole of the DiscCatcher, but I'm just making sure.

Thanks!

[ERicJ]

In short a "wheel" is probably the most common way to measure courses. And unless you're very careful can be somewhat error prone. Wheels also don't measure holes with water between the tee and basket; you have to attempt to measure a parallel path.

Laser range finders are preferred for accuracy and significant ease of use, but are more expensive. Downside of laser is that it requires line-of-sight. A good handheld GPS unit can solve that problem.

As for what to measure, i.e. line-of-sight vs. recommended flight path, that is a matter of debate. IIRC there are a couple theads on that topic over on the PDGA discussion board. My personal preference is line-of-sight.

[gameboy9]

Eric:
I did see those laser range finders you were talking about at the Home Depot yesterday afternoon, but they only did 100 ft maximum, so I did pick up a small 4" diameter wheel, so I'll make sure I measure it in a nice and slow pace, but fortunately the course isn't bumpy, and there isn't any water holes that you were mentioning.

I'll probably do shortest distance to the pin unless there are really thick trees, so probably the line-of-sight distance you were talking about, and we'll see how it goes. If I'm +/- 2 feet, I'll be happy.

Thanks for your help. :)

[heelboycraig]

Ball golf courses measure using the center of the fairway from the tee to the green. If you use the shortest path, i.e. measure along the left side of the fairway on a dogleg left, there will be a slight discrepancy of distance between the "shortest path" and the center of the fairway.

[ERicJ]

Eric:
I did see those laser range finders you were talking about at the Home Depot yesterday afternoon, but they only did 100 ft maximum. [...] If I'm +/- 2 feet, I'll be happy.
If you saw 100' max, I'm not sure you were looking at the right hardware. Here's an example of what I'm talking about: http://www.opticsplanet.net/rangefinders1.html

If you get +/- 2' that's fantastic accuracy.

[ERicJ]

Ball golf courses measure using the center of the fairway from the tee to the green. If you use the shortest path, i.e. measure along the left side of the fairway on a dogleg left, there will be a slight discrepancy of distance between the "shortest path" and the center of the fairway.Agreed, but ball golf courses almost always have well defined fairways, thus making it obvious to all players where the measurements would be. Fairways in our sport are often not-so-obvious to non-existent.

[heelboycraig]

Agreed, but ball golf courses almost always have well defined fairways, thus making it obvious to all players where the measurements would be. Fairways in our sport are often not-so-obvious to non-existent.

And that's where the fun begins. I actually wish course maps did follow the ball golf maps, and mark various distances to the pin - 100, 150 ft to pin, for example. That'd be a huge help on holes where depth perception is an issue.

[ERicJ]

My course map (http://www.dgcoursereview.com/course_files/2576/3889b8f0.jpg) for Quail Valley CC - the LINKS (http://www.dgcoursereview.com/course.php?id=2576) has distances off the tee for all the water hazards and major landmarks relevant to them. This was the first map I made for the Houston area courses.

[Olorin]

After you get your measurements, because of all the inaccuracy and estimation I'd suggest that you round your lengths to the nearest ten. That's better than the accuracy you can really get and all that players need. You could even round to the nearest 5 ft., but IMO, to round to the nearest foot is ludicrous, misleading, and unnecessary. I bet that when 99% of players see a length of 183 they just convert in their head to 180 anyway. Rounding just makes it easier from the start.

P.S.- Personally I think that measuring by the flight of the disc makes the most sense, but often harder to do. Why measure a straight line that no correctly thrown disc will ever take?

[gameboy9]

Eric: Ah... Now I gotcha with those range finders, but I think that that would be way too expensive for only measuring a few courses. :(

Meanwhile, I appreciate all of the advice! So now I think I'll try going down the center of the course if there's a dogleg, and probably going down a straight line if there isn't, and rounding to the nearest... probably 10. I guess I could add 10%-20% to account for "disc curving". (sorry, I don't know all the terms yet) Maybe that will make things at least somewhat accurate?

[ERicJ]

Olorin & I have disagreed on this subject in the past, and I will respectfully do so again.

After you get your measurements, because of all the inaccuracy and estimation I'd suggest that you round your lengths to the nearest ten. That's better than the accuracy you can really get and all that players need. You could even round to the nearest 5 ft., but IMO, to round to the nearest foot is ludicrous, misleading, and unnecessary. I bet that when 99% of players see a length of 183 they just convert in their head to 180 anyway. Rounding just makes it easier from the start.

If you want to round for the purpose of comprehension (http://en.wikipedia.org/wiki/Significant_digits#Comprehension), then so be it.

But I think the accuracy of your measurement tool should dictate the level of precision you report in your measurements. Does your wheel have an accuracy specification (http://www.contractor-books.com/CI/DigiRollerP2.htm)?

Reporting a measurement more accurate than your tool is capable of is one form of error. Rounding to anything less than your accuracy spec is another form (http://en.wikipedia.org/wiki/Significant_digits#Identifying_significant_digits) , or at least leaves an ambiguity.

Personally, when I see a course that has measurement all rounded to the 10's I question whether or not it was really measured or just guesstimated.

P.S.- Personally I think that measuring by the flight of the disc makes the most sense, but often harder to do. Why measure a straight line that no correctly thrown disc will ever take?

Why do distance competitions measure line-of-sight? If you're practicing drives on a football field and you throw a big hyzer goal line to goal line, do you say you threw 300' or 355'?

Practically speaking the only distance that is universally the same to every player is GPS point-to-point or line-of-sight.

Even if you used a mapping GPSr and plotted your course as you walked/wheeled the flight path and then printed that exact path on the tee sign map, you've still failed to compensate for the elevation changes of the disc in flight.


In the end all of this makes little difference to the actual playing of the game for most people... but is fun fodder for discussion boards. :)

[Olorin]

Even if you used a mapping GPSr and plotted your course as you walked/wheeled the flight path and then printed that exact path on the tee sign map, you've still failed to compensate for the elevation changes of the disc in flight.

Hey, we do agree on something! :D These two reasons are exactly why I say it's good enough to round off to 5s or 10s. On top of that very few discs would follow the exact path that your measured anyway, so even if you did have the accuracy to measure to the foot only a very small amount would go that actual distance.

[gameboy9]

Well, I can tell you that as I was measuring, the wheel kept going back and forth slightly from my line, probably because of all the small bumps on the course. So I rounded to the nearest 5, I figured that that would be best, but I did keep the measurements by the inch in case I change my mind. :) I also went straight line, trying to get the shortest distance possible.

I figure that this seems to be the best way to do it... but then again, I'm a newbie to this sport, so.......:rolleyes:

[ERicJ]

It's pretty cool that you're doing more than the average Joe to improve the sport/course for others. :) Glad to see that! Keep up the great work. If this sport is going to grow it needs people like you, new blood, taking an initiative and making things better.

[Donovan]

With trees and such as obstacles, I think the GPS measurement is the best route. It keeps things consistent. I mean how is someone going to use a when over a pond? Anyway that is my 2 cents on this matter. However, I totally understand people using other forms to measure when mot having access to GPS.

[ERicJ]

Just an FYI on accuracy. A decent laser range finder has accuracy of +/- 3ft. A decent GPSr with WAAS (http://www8.garmin.com/aboutGPS/waas.html) enabled is typically +/- 10ft. Of course that assumes both tools are being used properly, as with just about everything they are subject to human error in use.

[Donovan]

Just an FYI on accuracy. A decent laser range finder has accuracy of +/- 3ft. A decent GPSr with WAAS (http://www8.garmin.com/aboutGPS/waas.html) enabled is typically +/- 10ft. Of course that assumes both tools are being used properly, as with just about everything they are subject to human error in use.

That is most certainly true. Of course to use the laser, you do need to see the basket, yes? ;)

[Shank]

Google Earth is a free download. I have been using this trying to get together a couple proposals to present to the city. You can measure distance on this and it shows elevation changes.

I think to be totally accurate a GPS is probably your best bet. Maybe a survey coming out.

[Midnightbiker]

Eric: Ah... Now I gotcha with those range finders, but I think that that would be way too expensive for only measuring a few courses. :(

Meanwhile, I appreciate all of the advice! So now I think I'll try going down the center of the course if there's a dogleg, and probably going down a straight line if there isn't, and rounding to the nearest... probably 10. I guess I could add 10%-20% to account for "disc curving". (sorry, I don't know all the terms yet) Maybe that will make things at least somewhat accurate?


You should try Craig's List in your area. If you don't see one, just post an ad in the "Wanted " section. I was looking for a 300ft tape measure to mark off my practice field. The cheapest I could find at the store were almost $30. I really didn't want to spend that much, so I put an ad out of Craig's List that I was looking for one, and I got several offers. I was able to get a 330' tape measure for $10.

[PA_Disc]

Just an FYI on accuracy. A decent laser range finder has accuracy of +/- 3ft. A decent GPSr with WAAS (http://www8.garmin.com/aboutGPS/waas.html) enabled is typically +/- 10ft. Of course that assumes both tools are being used properly, as with just about everything they are subject to human error in use.

There are many GPS mapping systems that will get you with in Sub-foot distances. Many trimble enabled constrution equipment have an accuracy with in 0.1' or about 1.25"

[ERicJ]

There are many GPS mapping systems that will get you with in Sub-foot distances. Many trimble enabled constrution equipment have an accuracy with in 0.1' or about 1.25"Right, that's why I said "decent GPSr" For a couple hundred dollars you can get +/- 10ft (in my experience my eTrex Vista HCx is more like +/- 8ft).

Many of the +/- 1m accuracy units still require post processing of the data after downloading from a handheld to a computer. Back when I was pricing those they were around $1000. If you wanted real-time accuracy of +/- 1m it was more like $2000. I'm scared to think what a 0.1ft unit would cost....

[garublador]

Many of the +/- 1m accuracy units still require post processing of the data after downloading from a handheld to a computer. Back when I was pricing those they were around $1000. If you wanted real-time accuracy of +/- 1m it was more like $2000. I'm scared to think what a 0.1ft unit would cost....They actually use two units, the moving unit and a base station. You can either enter in the exact coordinates of the base station or let it aquire it's postision over a period of time. Because the base station knows exactly where it is and because it is near the moving unit, it is able to measure any error in the signals being broadcast by the satilites. It can then broadcast the error to the moving unit which adjusts for that error and that improves the accuracy. If your unit is moving you can also use accelerometers and gyros to "smooth" your GPS signal (since you'll know any acceleration and can calculate speed and direction from that) and gain more accuracy.

In other words, take whatever cost it is to get good accuracy and multiply it by at least two to get really good accuracy.

[PA_Disc]

^^What he said. I was just saying that they have more accurate insturments out there thats all. You would need to hire a "professional" if you wanted to get readings that accurate.

[ERicJ]

Here's an example of a Thales/Magellan handheld GPSr (~$1500) that provides real-time +/- 3m accuraccy and sub 1m accuracy after post-processing:
http://www.tigergps.com/thalesmobilemapperpro.html

Here's the white-paper on how they do the post-processing:
http://pro.magellangps.com/en/support/faq/mm_post_processing.asp

Several months ago, there were a couple of these up on ebay for $500 each, but that was just too much dinero.


The newer MobileMapper CX provices sub 1m accuracy in real-time and sub 1ft after post-processing:
http://pro.magellangps.com/en/products/product.asp?PRODID=1292
~$2500 with the post-processing software!

[McMarkD]

I think google earth is the best way to measure a course. There is a ruler tool, you can zoom in on the tee box click and the basket and you are done. It doesn't have the inaccuracies of going up and down hills and it is easy to measure distances around trees, for your "flight path" measurements. Much easier and better than the wheel, and simple. Dirt tee boxes are a little harder, but not impossible.

[ERicJ]

I think google earth is the best way to measure a course.Google Earth can be used to give you an easy, approximate measurement in lieu of actually being able to get out on the course. But there's no substitute for being there.

Google Earth has some accuracy issues (http://en.wikipedia.org/wiki/Google_Earth#Resolution_and_accuracy). Among the issues are outdated imagery and lower resolution (15m/pixel in some areas) imagery. And with any tool user error is a factor.

Google Earth is a very nice tool for making maps of courses, but like I said for measuring courses there's no substitute for being there.

My $0.02,
ERic