|
Phanatic posted:That's loving great. Barometric pressure at the exact same altitude (say, PHL), has varied from 30.06" to 29.36" over the past two days. That's a variance of 23.7 hPa, or almost 200 meters of altitude. The precision of the sensor is different from the accuracy of the measurement. The reported change was in barometric pressure, not in altitude.
|
#
?
Feb 16, 2017 05:32
|
|
|
|
| # ? May 17, 2024 17:12 |
|
|
drat, i guess i need to stop using my iphone as the sole sensor to record this mission critical altitude data
|
|
#
?
Feb 16, 2017 05:42
|
|
|
Keiya posted:The reported change was in barometric pressure, not in altitude. Yes, exactly. The regular changes in barometric pressure at *constant altitude* are considerably greater than the change in barometric pressure that results from a 3' altitude change. Using a barometer to tell you your altitude and expecting more than reasonably rough idea is unrealistic even if the sensor spec says it's accurate to .12 hPa. There's a reason that RADALT is a thing and it's not that barometers can give you a really accurate altitude reading.
|
|
#
?
Feb 16, 2017 05:59
|
|
|
Phanatic posted:That's loving great. Barometric pressure at the exact same altitude (say, PHL), has varied from 30.06" to 29.36" over the past two days. That's a variance of 23.7 hPa, or almost 200 meters of altitude. The precision of the sensor is different from the accuracy of the measurement. I mean, this is all true, but the sensor will read a different pressure at your head than at the ground, regardless of what ambient pressure is, and will register the same difference in pressure altitude thus.
|
|
#
?
Feb 16, 2017 06:02
|
|
|
The device never claimed to be an accurate altimeter. It claimed to be an accurate barometer, and it is. The variations in pressure could be due to any combination of altitude, temperature, wind, or your furnace, but that’s not the device’s problem. It’s like complaining that a metre stick doesn’t measure the length of a red‐hot bar of iron accurately because when the iron cools down, it has shrunk by a few millimetres.
|
|
#
?
Feb 16, 2017 06:10
|
|
|
Phanatic posted:Yes, exactly. The regular changes in barometric pressure at *constant altitude* are considerably greater than the change in barometric pressure that results from a 3' altitude change. Using a barometer to tell you your altitude and expecting more than reasonably rough idea is unrealistic even if the sensor spec says it's accurate to .12 hPa. There's a reason that RADALT is a thing and it's not that barometers can give you a really accurate altitude reading. If it consistently shows about the same difference when you hold it at head height and by your feet you can reasonably conclude that that difference comes from the altitude factor though. It's not like anyone here said we should replace radar altimeters with barometers, just that yeah, you CAN detect the pressure difference over a couple meters height if you want to.
|
|
#
?
Feb 16, 2017 06:36
|
|
|
 
|
|
#
?
Feb 16, 2017 06:57
|
|
|
Keiya posted:If it consistently shows about the same difference when you hold it at head height and by your feet you can reasonably conclude that that difference comes from the altitude factor though. It's not like anyone here said we should replace radar altimeters with barometers, just that yeah, you CAN detect the pressure difference over a couple meters height if you want to. I just tested it again with my phone five times, allowing five seconds in each position for the reading to stabilize, and here are the results CEILING (hPa) 1012.3 1012.3 1012.2 1012.3 1012.2 FLOOR (hPa) 1012.1 1012.1 1012.1 1012.1 1012.0 someone who gives a poo poo is free to perform statistics and determine the error rate and explain why my phone actually isn't able to measure the pressure change between the floor and the ceiling because it is 1985 and it sure doesn't seem possible to put a barometer that accurate in something that tiny! Phanatic posted:Yes, exactly. The regular changes in barometric pressure at *constant altitude* are considerably greater than the change in barometric pressure that results from a 3' altitude change. Using a barometer to tell you your altitude and expecting more than reasonably rough idea is unrealistic even if the sensor spec says it's accurate to .12 hPa. There's a reason that RADALT is a thing and it's not that barometers can give you a really accurate altitude reading. Yes no loving poo poo. Airplane pilots have been aware of this for a hundred years and every barometric altimeter includes a calibration wheel that the pilot uses to dial in the instrument so that the indicated pressure altitude is a reasonable representation of the true altitude above sea level. The pressure changes, but slowly enough that the barometric altimeter remains a useful instrument that usually only needs to be calibrated once at the beginning of the flight. Sagebrush fucked around with this message at 07:17 on Feb 16, 2017 |
|
#
?
Feb 16, 2017 07:11
|
|
|
current sea level pressure (20 minutes ago) in San Francisco: 1015.9 hPa phone reported pressure: 1011.9 hPa estimated altitude where 30' = 1 hPa: 120 feet GPS-reported altitude: 75 feet difference: 45 feet, ~1.5hPa so even the absolute value is pretty loving close, well under 1% accuracy across the expected range (from the ocean to let's say the top of Mt. Whitney, where the air pressure is roughly half that at sea level) and the relative accuracy is far better than that
|
|
#
?
Feb 16, 2017 07:23
|
|
|
|
|
#
?
Feb 16, 2017 07:26
|
|
|
Which one of you is the fishmech alt account?
|
|
#
?
Feb 16, 2017 07:58
|
|
|
I can't even tell if you guys are arguing or not because none of that poo poo makes sense, or matters.
|
|
#
?
Feb 16, 2017 08:30
|
|
|
Grem posted:I can't even tell if you guys are arguing or not because none of that poo poo makes sense, or matters. Don't feel too pressured about it.
|
|
#
?
Feb 16, 2017 08:45
|
|
|
Usually if it's not three ladders zip tied together I can't see what's wrong with these things until someone explains it. This one I See what's wrong with it.
|
|
#
?
Feb 16, 2017 09:23
|
|
|
Krinkle posted:Usually if it's not three ladders zip tied together I can't see what's wrong with these things until someone explains it. I do not see what's wrong with it, and would like to. I should say, I don't know what function that's even serving, much less how it's serving it dangerously.
|
|
#
?
Feb 16, 2017 10:17
|
|
|
ArgumentatumE.C.T. posted:I do not see what's wrong with it, and would like to. I should say, I don't know what function that's even serving, much less how it's serving it dangerously. The pipe goes through the U then the bolts hold the U and consequentially, the pipe, in place. Instead the pipe is held in place by two tiny nuts. Much like my posts.
|
|
#
?
Feb 16, 2017 10:27
|
|
|
It's not like pressure is going to kill you or anything. https://www.youtube.com/watch?v=9TbocZ42XJg
|
|
#
?
Feb 16, 2017 11:31
|
|
|
Turtlicious posted:The pipe goes through the U then the bolts hold the U and consequentially, the pipe, in place. Or there would be a plate on the other side of the pipe that the nuts would hold secure. But for that installation reversing the U would be better.
|
|
#
?
Feb 16, 2017 11:39
|
|
|
Turtlicious posted:The pipe goes through the U then the bolts hold the U and consequentially, the pipe, in place. I sometimes do stuff like that when I'm mocking things up to just hold things approximately correct while I take measurements/angles/tack plates approximately into place for future IPCRESS to sort out/grind off plates past IPCRESS tacked in the wrong place. So I'm hopeful that this isn't the finished product. Using a gas bottle as a stool isn't a great plan even when you aren't doing hot work. At least he's not welding the rim, I guess?
|
|
#
?
Feb 16, 2017 12:56
|
|
|
IPCRESS posted:I sometimes do stuff like that when I'm mocking things up to just hold things approximately correct while I take measurements/angles/tack plates approximately into place for future IPCRESS to sort out/grind off plates past IPCRESS tacked in the wrong place. So I'm hopeful that this isn't the finished product. The holes through the I-beam are too close together, too. Even it it is flipped around, that's not going to seat properly.
|
|
#
?
Feb 16, 2017 13:51
|
|
|
BlankIsBeautiful posted:The holes through the I-beam are too close together, too. Even it it is flipped around, that's not going to seat properly. Maybe that's why it's on backwards to begin with.
|
|
#
?
Feb 17, 2017 02:25
|
|
|
Turtlicious posted:The pipe goes through the U then the bolts hold the U and consequentially, the pipe, in place. It's held in place with barometric pressure, which means if it moves 15 feet below sea level it won't work. That's what that derail was about, right?
|
|
#
?
Feb 17, 2017 02:50
|
|
|
Sagebrush posted:Yes no loving poo poo. Airplane pilots have been aware of this for a hundred years and every barometric altimeter includes a calibration wheel that the pilot uses to dial in the instrument so that the indicated pressure altitude is a reasonable representation of the true altitude above sea level. The pressure changes, but slowly enough that the barometric altimeter remains a useful instrument that usually only needs to be calibrated once at the beginning of the flight. Flying above FL180 with an altimeter accurate to mean sea level is OSHA as gently caress. shame on an IGA fucked around with this message at 03:02 on Feb 17, 2017 |
|
#
?
Feb 17, 2017 03:00
|
|
|
Nut chat reminds me of the Hyatt Regency walkway collapse The original design for the walkway suspension sucked rear end. It would have required the suspended rods to be threaded for half their length, and nuts to be screwed on to the rods this full distance - meaning minor nicks or scratches on when installing the rods could render them unable to be threaded in place. So a minor change was made: instead of continuous rods, the rods stopped at the upper walkway and a new set then carried the lower. However, this alteration meant that the nuts supporting the upper level were also bearing the weight of the lower level. When the walkway was crowded for a function, the nuts simply pulled straight through the beams and the walkways dropped to the atrium floor, killing 114 people. The resulting investigation determined that even the original design would have only supported 60% of the required load.
|
|
#
?
Feb 17, 2017 03:20
|
|
|
Half assed, indoor, pedestrian suspension bridge. Always a good idea. Would this bullshit have worked if there were extra layers of plate where the rods passed through, or if there were more rods? Or is it just a stupid rear end design that was destined to fail.
|
|
#
?
Feb 17, 2017 03:54
|
|
|
Bloody Hedgehog posted:I mean, yeah, the problem with americas crumbling infrastructure isn't for lack if it being inspected. All of it gets inspected to hell and back, it just that once the reports are turned in, the beancounters go "Sorry, no money.", and poo poo is left to rot. Counterpoint: Seattle is spending billions to dig a tunnel through downtown so they can remove the above-ground viaduct in case "the big one" hits.
|
|
#
?
Feb 17, 2017 04:08
|
|
|
Is a tunnel really better than an above-ground viaduct in a giant earthquake?
|
|
#
?
Feb 17, 2017 04:08
|
|
|
That the original designs where also lackluster is news to me, and yes the threading idea was purely form over function and the on-site redesign was warranted. But the basic idea is sound; instead of screwing things on you could have just used strong clamps, welding, or whatnot. Assuming the suspending pipe was securely fastened to the ceiling, that is.
|
|
#
?
Feb 17, 2017 04:09
|
|
|
wdarkk posted:Is a tunnel really better than an above-ground viaduct in a giant earthquake? Yeah, it'll fill with water which will put out all the car fires.
|
|
#
?
Feb 17, 2017 04:09
|
|
|
wdarkk posted:Is a tunnel really better than an above-ground viaduct in a giant earthquake? The viaduct would fall over onto thousands of people. A tunnel would not.
|
|
#
?
Feb 17, 2017 04:13
|
|
|
HEY NONG MAN posted:The viaduct would fall over onto thousands of people. A tunnel would not. Ok that is a difference.
|
|
#
?
Feb 17, 2017 04:22
|
|
|
Saves on burial costs too.
|
|
#
?
Feb 17, 2017 04:30
|
|
|
Vanagoon posted:Half assed, indoor, pedestrian suspension bridge. Always a good idea. I saw this in a documentary and they said larger washers under each nut could have solved the whole problem.
|
|
#
?
Feb 17, 2017 04:34
|
|
|
ArgumentatumE.C.T. posted:I saw this in a documentary and they said larger washers under each nut could have solved the whole problem. They should have built the whole bridge out of the washer material.
|
|
#
?
Feb 17, 2017 04:35
|
|
|
HEY NONG MAN posted:The viaduct would fall over onto thousands of people. A tunnel would not. See also: 1989 Loma Prieta earthquake, Cypress Viaduct collapse https://en.wikipedia.org/wiki/1989_Loma_Prieta_earthquake#Oakland_and_Interstate_880.2FCypress_Viaduct E: from that same wiki article: quote:The BART rail system, which hauled commuters between the East Bay and San Francisco via the Transbay Tube, was virtually undamaged and only closed for post-earthquake inspection. Subway good, elevated highway bad. FuturePastNow fucked around with this message at 05:07 on Feb 17, 2017 |
|
#
?
Feb 17, 2017 04:57
|
|
|
Whoops.quote:Carbon monoxide poisoning is suspected as the cause of death for three family members found dead at the bottom of a concrete water tank in the Southern Tablelands of NSW.
|
|
#
?
Feb 17, 2017 06:20
|
|
|
I grew up across the street from a guy who was pressure washing his pool while standing in it. Somehow the pressure washer fell in and he got electrocuted killing him instantly. His oldest son jumped in after him thinking he had a heart attack and was killed as well. My family and theirs were pretty close but after that poo poo happened the wife and the 2 younger sons moved. It's just hosed up to know they were rushing to help out of instinct and lost their lives for it. Dudes bad decision not only cost him but his 18 year old son as well.
|
|
#
?
Feb 17, 2017 08:55
|
|
|
Oversize.
|
|
#
?
Feb 17, 2017 10:08
|
|
|
Thats not a nice thing to say about Peter Tippett
|
|
#
?
Feb 17, 2017 10:09
|
|
|
|
| # ? May 17, 2024 17:12 |
|
|
Say Nothing posted:Oversize. haha yeah, drive anywhere in central queensland and your dodging those loving things all the time.
|
|
#
?
Feb 17, 2017 10:30
|
|
