freakydiver 0 #1 February 2, 2005 I got my new Neptune - question though. Its just sitting on my desk at home and from time to time I look at the Alti listed for MSL and MAN does it vary. This scares me. It varies quite a bit from day to day. Am I supossed to trust this alti when in freefall or canopy mode???? Has anyone else noticed this??? -- (N.DG) "If all else fails – at least try and look under control." -- Quote Share this post Link to post Share on other sites
ianmdrennan 2 #2 February 2, 2005 barometric pressure varies all the time. The important thing is that the Alti is zero'd (which it does after landing) before each jump. Blues, IanPerformance Designs Factory Team Quote Share this post Link to post Share on other sites
freakydiver 0 #3 February 2, 2005 I'm just wondering though - I've watched the MSL sit here and vary up to 40 feet in a few seconds. What is to prevent that from happening in the air?? Or after it zeros on the ground per se??? -- (N.DG) "If all else fails – at least try and look under control." -- Quote Share this post Link to post Share on other sites
ianmdrennan 2 #4 February 2, 2005 I think you'd have to contact alti-2 for any answers like that. Assuming your pressure sensor is functioning correctly, bear in mind that what you're seeing will happen on ANY altimeter. It's just more noticable when you can see increments of 10 feet Drop alti-2 an email, I'm sure they can address any concerns you may have. Blues, IanPerformance Designs Factory Team Quote Share this post Link to post Share on other sites
freakydiver 0 #5 February 2, 2005 Ok - reading the manual - it says: "The 'MSL' value is actually "QNE" or "Pressure Alti" which means that the value will change with barometric pressure. It is normal for the MSL reading to vary as much as +-300 feet." Makes sense - just like you said Ian. My question I guess to the makers of this alti - what does freefall alti and canopy alti work from then if this +-300 foot QNE MSL alti can vary as much as it can......... -- (N.DG) "If all else fails – at least try and look under control." -- Quote Share this post Link to post Share on other sites
ianmdrennan 2 #6 February 2, 2005 Quotewhat does freefall alti and canopy alti work from then if this +-300 foot QNE MSL alti can vary as much as it can......... I believe same as a regular alti. Zero based off of takeoff setting, but I'm guessing cause I don't know the inner workings of it's software. Alti-2 have always been very good about responding to Q's. Drop them an email (Lara), I'm sure they'll be happy to address any questions you may have. Blues, IanPerformance Designs Factory Team Quote Share this post Link to post Share on other sites
pilotdave 0 #7 February 2, 2005 That's +/- 300 feet variation from day to day, not second to second. They're saying that at a typical location, the barametric pressure will typically vary that much. With an analog altimeter, you've gotta zero it every day. It might be off by as much as +/- 300 feet from the last time it was zeroed. A 300 foot shift in pressure altitude during the day would be a good sign of some nasty weather about to hit. I don't know why they chose to display "MSL." The number is not particularly useful, unless you want to compute density altitude. And it shouldn't really be labeled MSL since it's really pressure altitude, a completely different thing. If you think yours is varying too much, you might want to go into demo mode and see whats happening in all the different modes... aircraft, freefall, and canopy mode. It should not say that you're doing a 2000 fpm climb when sitting on the ground. But it will occasionally show "very slow climb" when it senses a pressure change. Dave Quote Share this post Link to post Share on other sites
freakydiver 0 #8 February 2, 2005 I've seen it vary 20-40 feet in the matter of seconds. More than once. Maybe this is normal - you wouldn't "see" that type of change on an analog altimeter - the needle would barely move... -- (N.DG) "If all else fails – at least try and look under control." -- Quote Share this post Link to post Share on other sites
BIGUN 1,483 #9 February 2, 2005 Quotewhen Neptune is in ground mode it is acting like a barometer and giving you an approximate value of MSL which will vary with barometric pressure, on any given day it may vary by 300'. As soon as Neptune senses a takeoff, it will lock in the last MSL reading which ensures that the AGL (above ground level) indication is accurate. http://www.alti-2.com/Neptune_Owners_Pages/Altitude_Displays.htmNobody has time to listen; because they're desperately chasing the need of being heard. Quote Share this post Link to post Share on other sites
EDYDO 0 #10 February 2, 2005 I contacted Alti-2 about that same thing over a year ago. Essentially what has been said in this thread is correct. Although the label is MSL, that is not what it is, so trying to read it as "feet" will make no sense at all. I was told it was a pressure reading and they decided to make it available just in case anybody cares. In my opinion, it has mostly caused confusion. I quit looking at it. LOVE MY NEPTUNE Ed Quote Share this post Link to post Share on other sites
freakydiver 0 #11 February 2, 2005 This is the key: "As soon as Neptune senses a takeoff, it will lock in the last MSL reading which ensures that the AGL (above ground level) indication is accurate." Bottom line is use your eyes above all other methods for reading alti - I always have and always will... -- (N.DG) "If all else fails – at least try and look under control." -- Quote Share this post Link to post Share on other sites
CygnusX-1 43 #12 February 2, 2005 Quoteso trying to read it as "feet" will make no sense at all. I wondered about that. When jumping at DeLand, I've noticed that the MSL would read something like -300. I don't really know but if I truely was -300 feet MSL here in Florida, I would probably be under water. Although, I think I would be concerned if I saw the reading change by 40 within a couple of minutes. Quote Share this post Link to post Share on other sites
EDYDO 0 #13 February 2, 2005 Quote The Neptune should be cool tho!!! Cool it is!!! I have been amazed at the accuracy of this altimeter. I occasionally glance at it when low, just because it is so amazing. If it says 20 feet, it is!!! I have watched in amazement during climbout when another Neptune is in sight and the 100 foot increments click off on both at the exact same instant all the way to altitude. I have no idea how they can be that consistent!!!??? Ed Quote Share this post Link to post Share on other sites
diablopilot 2 #14 February 3, 2005 QuoteI've watched the MSL sit here and vary up to 40 feet in a few seconds. if 40 feet makes a difference in freefall you f-ed up along time ago......---------------------------------------------- You're not as good as you think you are. Seriously. Quote Share this post Link to post Share on other sites
indyz 1 #15 February 3, 2005 QuoteI've seen it vary 20-40 feet in the matter of seconds. More than once. Maybe this is normal - you wouldn't "see" that type of change on an analog altimeter - the needle would barely move... Sudden indoor pressure changes aren't unusual. It could be happening as a result of a door opening/closing, a forced-air heating system coming on, or wind or stack effect. Quote Share this post Link to post Share on other sites
Tonto 1 #16 February 3, 2005 QuoteA 300 foot shift in pressure altitude during the day would be a good sign of some nasty weather about to hit. Or some good weather about to arrive.. tIt's the year of the Pig. Quote Share this post Link to post Share on other sites
pilotdave 0 #17 February 3, 2005 The glass is half empty damnit! Dave Quote Share this post Link to post Share on other sites
freakydiver 0 #18 February 3, 2005 lmao - im going to mess around with opening and closing doors to see what happens... -- (N.DG) "If all else fails – at least try and look under control." -- Quote Share this post Link to post Share on other sites
freakydiver 0 #19 February 3, 2005 LOL That's what I've been thinking this whole time... I haven't had an alti in quite awhile so it will be weird anyhow I tell all new skydivers - use your EYES as your primary alti, I think its the best skill I ever learned - its saved my ass many a time... -- (N.DG) "If all else fails – at least try and look under control." -- Quote Share this post Link to post Share on other sites
kelpdiver 2 #20 February 3, 2005 QuoteLOL That's what I've been thinking this whole time... I haven't had an alti in quite awhile so it will be weird anyhow I tell all new skydivers - use your EYES as your primary alti, I think its the best skill I ever learned - its saved my ass many a time... sure, but are your eyes accurate to 40ft? Quote Share this post Link to post Share on other sites
freakydiver 0 #21 February 3, 2005 Mine are I do believe... But what I meant was, for newer jumpers to use their eyes as "freefall" altimeters. You don't really have to pay attention to low altitude all that much unless you are swooping. -- (N.DG) "If all else fails – at least try and look under control." -- Quote Share this post Link to post Share on other sites
kelpdiver 2 #22 February 3, 2005 QuoteMine are I do believe... But what I meant was, for newer jumpers to use their eyes as "freefall" altimeters. You don't really have to pay attention to low altitude all that much unless you are swooping. I do agree with you fully on this. I'd like to be better at it before I take advantage of the great new prices for Dytters. But short of a malfunction, the neptune is more accurate than you are in freefall, and stays that way even going to a new DZ. Under canopy I'd imagine an experienced person could be as accurate. Quote Share this post Link to post Share on other sites
