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Janos Bauer wrote:
Marc Ramsey wrote: It has nothing to do with competence. I agree with some of your opinions, others do not. I mean, you usually aware of the technical background (security, GPS issues, etc-etc). On the other hand you often refuse certain suggestions referring to existing rules and not to technical problems. So, I must not be truly competent 8^) Tradition is a big factor. The perceived (but not adequately studied, in my opinion) inaccuracy of GPS altitude is another. I also haven't really studied it but last Sunday it was the second time when I had to fly xc without variometer and I was happy with the simple GPS (no WAAS etc.) based palm&soaringpilot combo. I think it would be impossible if there was really huge error (bigger than on those 20 year old barographs). You are comparing apples to oranges. GPS measures geometric altitude with a typical error of, say, +/- 50 feet. Barographs measure calibrated pressure altitude with a typical error of, say, +/- 50 feet. GPS altitude can not be corrected to pressure altitude with reasonable error bounds, unless specific meteorological data is provided for the time and place of the flight. Pressure altitude can not be corrected to geometric altitude with reasonable error bounds, unless specific meteorological data is provided for the time and place of the flight. Without making these meteorological corrections, geometric and calibrated pressure altitude can differ by as much as 1000 feet for a Diamond altitude gain. It doesn't matter how they are treated, as long as they can be successfully calibrated within the set interval. The corrected pressure altitudes taken from a barogram may be off by a hundred feet or so, but they still provide a more accurate measurement of the precise form of altitude required by the current IGC rules, than any COTS GPS. I don't think they are calibrated for all the temperatures. There is no requirement that barographs be corrected for temperature. I don't think all the mechanical impacts can be handled by calibration (I myself (saw others do it few times) locked out the needle of one old smoky barograph and we had to bent it back to working position, how do you handle such an "impact"?) That barograph should have been marked as potentially faulty. An OO, if aware of this, should refuse to certify a flight using it until it is repaired and recalibrated. And the most important issue, what I stated befo neither barographs nor cameras are sealed by OO on most of the places I visited... The Sporting Code requires sealing the barograph, but not necessarily the cameras (SC3 4.6.3, 4.7.2). If an OO is unable to follow these simple rules, how likely is it that he/she will follow the more technically complex procedures that might be required for a COTS GPS? No one wants to cheat with them, it's just the way things going on some (maybe most) places. I've seen similar things. Given this, the obvious solution would be to award badges using the honor system. If this is not acceptable, then some level of procedural and/or technical security measures must be in the rules (even if some do not follow them). How much security is enough? Marc |
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Marc Ramsey wrote:
You are comparing apples to oranges. GPS measures geometric altitude with a typical error of, say, +/- 50 feet. Barographs measure calibrated pressure altitude with a typical error of, say, +/- 50 feet. GPS altitude can not be corrected to pressure altitude with reasonable error bounds, unless specific meteorological data is provided for the time and place of the flight. Pressure altitude can not be corrected to geometric altitude with reasonable error bounds, unless specific meteorological data is provided for the time and place of the flight. Without making these meteorological corrections, geometric and calibrated pressure altitude can differ by as much as 1000 feet for a Diamond altitude gain. The whole altitude task is about the ability to gain certain amount of energy from air (thermal, wave, something else). For me it's a geometric issue. If someone is able to get from A to B and the altitude difference is more than X than it's fine. Not the air pressure at that altitude qualifies the pilot. You already agree with it so what do we argue about? ![]() I don't think they are calibrated for all the temperatures. There is no requirement that barographs be corrected for temperature. Hmm, those thin metal plates and other small parts could behave quite differently at +40C than -40C (typical wave temperature at my country). That barograph should have been marked as potentially faulty. An OO, if aware of this, should refuse to certify a flight using it until it is repaired and recalibrated. Should. And the most important issue, what I stated befo neither barographs nor cameras are sealed by OO on most of the places I visited... The Sporting Code requires sealing the barograph, but not necessarily the cameras (SC3 4.6.3, 4.7.2). If an OO is unable to follow these simple rules, how likely is it that he/she will follow the more technically complex procedures that might be required for a COTS GPS? No they won't. No one wants to cheat with them, it's just the way things going on some (maybe most) places. I've seen similar things. Given this, the obvious solution would be to award badges using the honor system. If this is not acceptable, then some level of procedural and/or technical security measures must be in the rules (even if some do not follow them). How much security is enough? I would accept any trace file and a sign from the OO. Yes, from the same OO who doesn't seal the barograph. It's the same level of security as the current barograph+photo process. /Janos |
#3
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I've found it a little funny that there's all this fuss about
the measuring devices, yet I've read in several articles about silver badge flights and radio chatter and finding thermals despite: SC 3, 2.1.1 a "The Silver distance flight should be flown without navigational or other assistance given over the radio (other than permission to land on an airfield) or help or guidance from other aircraft." This sport has elements of the honor system in it already, there are already some who do cheat (most often inadvertently), but I for one think that the sport is so small that the overemphasis on security discourages participation to a much greater degree than any cheating under a COTS gps approval for badges would detract or discourage. No one wants to cheat with them, it's just the way things going on some (maybe most) places. I've seen similar things. Given this, the obvious solution would be to award badges using the honor system. If this is not acceptable, then some level of procedural and/or technical security measures must be in the rules (even if some do not follow them). How much security is enough? -- ------------+ Mark Boyd Avenal, California, USA |
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Hi
Without making these meteorological corrections, geometric and calibrated pressure altitude can differ by as much as 1000 feet for a Diamond altitude gain. Marc I do not know about the conversion process required to convert geometric and I assume the actual within the bounds of GPS error altitude, to pressure altitude. However given the assertion that the pressure altitude can differ by as much as 1000ft from the geometric altitude, does it imply that two pressure altitudes can actually differ by 2000ft? Would it not provide sufficient argument to switch to geometric altitude? Paul |
#5
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Paul Bart wrote:
I do not know about the conversion process required to convert geometric and I assume the actual within the bounds of GPS error altitude, to pressure altitude. However given the assertion that the pressure altitude can differ by as much as 1000ft from the geometric altitude, does it imply that two pressure altitudes can actually differ by 2000ft? Would it not provide sufficient argument to switch to geometric altitude? Yes, this is correct. You don't have to climb as high on a cold winter day, as you would on a hot summer day, to obtain a specific pressure altitude gain. But, I suspect some (maybe most?) would say that we have always measured pressure altitude is this sport, and that we should continue doing so... Marc |
#6
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![]() "Marc Ramsey" wrote in message . com... Paul Bart wrote: However given the assertion that the pressure altitude can differ by as much as 1000ft from the geometric altitude, does it imply that two pressure altitudes can actually differ by 2000ft? Would it not provide sufficient argument to switch to geometric altitude? Yes, this is correct. You don't have to climb as high on a cold winter day, as you would on a hot summer day, to obtain a specific pressure altitude gain. But, I suspect some (maybe most?) would say that we have always measured pressure altitude is this sport, and that we should continue doing so... Marc Hi Marc Thanks for your reply. Given the budding status of my gliding career, this is not likely to be an issue for me any time soon ![]() can *potentially* reduce an error, by up to 1000 ft it should be seriously considered. I wonder if the resistance to change is mainly due to the high average age of the gliding fraternity? Paul |
#7
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On Thu, 03 Jun 2004 13:52:29 GMT, "Paul Bart"
wrote: "Marc Ramsey" wrote in message .com... Paul Bart wrote: However given the assertion that the pressure altitude can differ by as much as 1000ft from the geometric altitude, does it imply that two pressure altitudes can actually differ by 2000ft? Would it not provide sufficient argument to switch to geometric altitude? Yes, this is correct. You don't have to climb as high on a cold winter day, as you would on a hot summer day, to obtain a specific pressure altitude gain. But, I suspect some (maybe most?) would say that we have always measured pressure altitude is this sport, and that we should continue doing so... Marc Hi Marc Thanks for your reply. Given the budding status of my gliding career, this is not likely to be an issue for me any time soon ![]() can *potentially* reduce an error, by up to 1000 ft it should be seriously considered. I wonder if the resistance to change is mainly due to the high average age of the gliding fraternity? I have a strong suspicion that climbing to a pressure altitude should present much the same difficulty regardless of which way it differs from the geometric altitude, but climbing to a geometric altitude will get easier as the pressure (and hence pressure altitude) rises. Unless I'm much mistaken, this could be used as an argument for retaining the pressure altitude for badges. What have I missed or misunderstood here? -- martin@ : Martin Gregorie gregorie : Harlow, UK demon : co : Zappa fan & glider pilot uk : |
#8
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Paul Bart wrote:
"Marc Ramsey" wrote in message Yes, this is correct. You don't have to climb as high on a cold winter day, as you would on a hot summer day, to obtain a specific pressure altitude gain. But, I suspect some (maybe most?) would say that we have always measured pressure altitude is this sport, and that we should continue doing so... Thanks for your reply. Given the budding status of my gliding career, this is not likely to be an issue for me any time soon ![]() can *potentially* reduce an error, by up to 1000 ft it should be seriously considered. But, using GPS altitude only reduces the error if we were measuring geometric altitude. Using GPS altitude under the present rules would *increase* the error, because we are presently measuring pressure altitude. I wonder if the resistance to change is mainly due to the high average age of the gliding fraternity? I'm not going to touch that one... Marc |
#9
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"Paul Bart" wrote in message news:x2Gvc.4102
however given that GPS can *potentially* reduce an error, by up to 1000 ft it should be seriously considered. I wonder if the resistance to change is mainly due to the high average age of the gliding fraternity? Paul You seem to have missed the frequently stated point that the difference is not an error. An error free measurement of pressure altitude will not be equal to an error free gps (geometric) altitude except under rare conditions. Recognition of this fact may have something to do with age, but the real issues are recognizing what is to be measured, why it is being measured, and then determining whether it is reasonable to change to measuring something else. Andy |
#10
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![]() "Andy Durbin" wrote in message om... "Paul Bart" wrote in message news:x2Gvc.4102 however given that GPS can *potentially* reduce an error, by up to 1000 ft it should be seriously considered. I wonder if the resistance to change is mainly due to the high average age of the gliding fraternity? Paul You seem to have missed the frequently stated point that the difference is not an error. An error free measurement of pressure altitude will not be equal to an error free gps (geometric) altitude except under rare conditions. No I did not. You are correct, I have incorrectly used the word error if one considers it's meaning in a relation to the output of the measuring device, however that was not my intention. Recognition of this fact may have something to do with age, but the real issues are recognizing what is to be measured, Height above ground I would have thought. If I understand the preceding discussion correctly, pressure altitude was used because there were no other viable options, not because it was a good measure of height above ground. why it is being measured, To either establish benchmark, or to fulfill some requirements. For each of these I would rather know the actual distance above ground, not a measure that depends on prevailing meteorological conditions. Unless, of course, you consider Martin's observation, that the effort to climb to a particular pressure altitude takes about the same effort regardless of the geometric altitude and also assuming that it is the effort that is important, rather then the actual height above ground. and then determining whether it is reasonable to change to measuring something else. Thank you for your observation. Paul |
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