As you know, USMS passed a rule that will require us to measure any pool in which we hold a meet, IF we want the times from that meet to count for USMS Top Ten. I'm trying to figure out the best way to do this - what sort of tape to buy, the best method to use, etc. (Can you tell that I'm an engineer?)
I'd like to hear from those of you who have measured pools. What brand of tape do you recommend? What length? (60 meters?) Any idea where I can buy such a tape? Any suggestions for how to get a good (accurate) measurement, especially over a 50 meter course?
FYI, below are the instructions on how to perform pool measurements, taken from the USMS Pool Length Certification Form.
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"A completed form must be on file or submitted with an application for sanction or recognition to your LMSC Sanctions Chairman. For pools utilizing bulkheads, completed forms from each session must be included with results sent to the Top Ten Chairman if the results are to be included in Top Ten submissions.
Measurement procedures:
--Measurements must be conducted using a measuring device with the minimum measuring quality of at least ± 0.005 m (±.0.20 inches or 0.016 feet) over the nominal distance. A laser based measuring device may be used but it must be as accurate as required for steel tapes. Tapes may not be combined to perform the measurements.
--Measurements may be reported in either the English system (feet/inches) or the metric system (meters/centimeters).
Instructions for pool length measurements:
--Measurements must be conducted for each lane. Inspect each end of the pool to insure that it is vertical. If there are any protrusions from the wall into the pool between 0.8 meters (2.5 feet) below the surface to the top of the touch pad or wall or up to 0.3 meters above the surface whichever is higher, you must use the protrusion as your measurement point. Otherwise, measurements must be taken in the center of each lane at water level.
--The measuring device shall be moved up/down and left/right at least 12 inches (unless you are on a protrusion) during each measurement and the minimum distance for each measurement recorded.
--Measurements may be conducted with or without touchpads in place. However, if touchpads are used the pool must still meet the length requirements with them in place.
--Permanent courses need only be measured once unless structural changes have occurred since original measurement.
--For pools with a moveable bulkhead, after each session a course measurement must be confirmed by a responsible person. Only the outside lanes and a single center lane need to be measured to confirm the integrity of the bulkhead and its placement."
Unfortunately, this discussion is split between two threads. So to answer questions on both:
The reality of what we are trying to do is that we cannot build pools that are either precise or accurate enough to say that the difference in time that we measure (0.01 second) is meaningful (if we assume the USA-S maximum length of +0.03 meters) for anything other than a sub 20-second 50-yard freestyle. So given that, what do we do? The best we can or get faster :) I have done the math and actually wrote a white paper that we used in our discussions about this issue. Part of the problem is that we have a lot of history from USA-S.
By trying to do our best, we attempt to eliminate pools that are without a question short. Most errors using a tape will cause the measurement to be longer than reality and therefore few pools should be falsely eliminated. There are two obvious exceptions to this: a bad tape and measurements in a high temperature. The former should be checked if one fails a pool and the latter can be corrected if necessary. As far as the errors the other way, a sagging tape was mentioned. At the 50-meter distance, the amount of sag necessary to make a significant difference is actually quite a bit (> 0.3 meters). Ignoring that the sage is not triangular (which means that the calculation overestimates the error), the error is less than 4 mm. With half that sag in a 25-meter pool, the error is under 2 mm.
Someone stated that USMS has no tolerances. The tolerance is -0.00 meter. That means that the pool must be less than 0.005 meters short. We set no maximum (after some debate) because we did not want to exclude any more pools than necessary.
Lasers have always presented a dilemma. Some bodies want to use them exclusively and I have advised them otherwise. I know that USA-S has used them for certifying a number of pools used in their championship and grand prix meets. Personally, the work required to set one up makes me want to go buy a tape.
I attended the "Our Kids Initiative" meeting last weekend in Indianapolis. In attendance were representatives from NFHS, NCAA, YMCA, NISCA, USA-Swimming and USMS. This was our first year being invited to this three-year-old gathering. The first topic on the agenda (at least the real part) was certification of pools. After the mess in Virginia Beach last year, it has become a major topic. Unfortunately, USA-Swimming doesn't have to worry too much since they don't set too many records. These other organizations only worry about the "big meets" and they do go out and spend the money to have a professional do the measurements. This includes measuring the bulkhead for every session if necessary.
So the bottom line here, IMHO, is that there are no simple answers even if you define what the true goal is. There are no acceptable answers to some of the questions.
Leo
Unfortunately, this discussion is split between two threads. So to answer questions on both:
The reality of what we are trying to do is that we cannot build pools that are either precise or accurate enough to say that the difference in time that we measure (0.01 second) is meaningful (if we assume the USA-S maximum length of +0.03 meters) for anything other than a sub 20-second 50-yard freestyle. So given that, what do we do? The best we can or get faster :) I have done the math and actually wrote a white paper that we used in our discussions about this issue. Part of the problem is that we have a lot of history from USA-S.
By trying to do our best, we attempt to eliminate pools that are without a question short. Most errors using a tape will cause the measurement to be longer than reality and therefore few pools should be falsely eliminated. There are two obvious exceptions to this: a bad tape and measurements in a high temperature. The former should be checked if one fails a pool and the latter can be corrected if necessary. As far as the errors the other way, a sagging tape was mentioned. At the 50-meter distance, the amount of sag necessary to make a significant difference is actually quite a bit (> 0.3 meters). Ignoring that the sage is not triangular (which means that the calculation overestimates the error), the error is less than 4 mm. With half that sag in a 25-meter pool, the error is under 2 mm.
Someone stated that USMS has no tolerances. The tolerance is -0.00 meter. That means that the pool must be less than 0.005 meters short. We set no maximum (after some debate) because we did not want to exclude any more pools than necessary.
Lasers have always presented a dilemma. Some bodies want to use them exclusively and I have advised them otherwise. I know that USA-S has used them for certifying a number of pools used in their championship and grand prix meets. Personally, the work required to set one up makes me want to go buy a tape.
I attended the "Our Kids Initiative" meeting last weekend in Indianapolis. In attendance were representatives from NFHS, NCAA, YMCA, NISCA, USA-Swimming and USMS. This was our first year being invited to this three-year-old gathering. The first topic on the agenda (at least the real part) was certification of pools. After the mess in Virginia Beach last year, it has become a major topic. Unfortunately, USA-Swimming doesn't have to worry too much since they don't set too many records. These other organizations only worry about the "big meets" and they do go out and spend the money to have a professional do the measurements. This includes measuring the bulkhead for every session if necessary.
So the bottom line here, IMHO, is that there are no simple answers even if you define what the true goal is. There are no acceptable answers to some of the questions.
Leo
