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quantumleap

SPECI's and altitude changes

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I had been seeing some of the altitude changes which others had reported and decided to look into why it may happen. I think I may have identified something and would like others to comment if this is what they see. If it is true, maybe the developers can come up with a solution.Currently Gander International (CYQX) in Newfoundland and Labrador is socked in with frequent changes in the visbility requiring SPECI's to be posted.Prior to the last SPECI, this was the METAR:METAR CYQX 210100Z 35005KT 5/8SM -RA BR VV002 04/03 A2948 RMK FG8SLP988=AS2004.5 handles this very nicely and the altimeter on the ground read correctly for the aerodrome elevation (496 feet).23 minutes later along comes a SPECI, and AS2004.5 picks it up.SPECI CYQX 210123Z 36003KT 3/8SM -RA FG VV002 RMK FG8=Note that for whatever reason (and I've seen this in many cases), the SPECI does not include an updated altimeter setting. What AS2204.5 seems to do is no longer use the previous altimter setting value (29.48) and sets it to the standard value (29.92). This of course causes the altitude displayed on the ground to drop about 440 feet.Agreed that this is on the ground, but it may also explain changes at other altitudes when the nearest station does not report a correct altimeter setting and so AS2004.5 reverts to standard values. Am I on the right track here?


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Hi,Thanks for that!AS has never mended old data with new data strictly for METAR reports (it does this only when TAF processing is in place).If the new METAR report does not contain an altimeter setting we will default it to 29.92. That seems to be what is happening in your case. It certainly may explain why some are having baro inconsistencies. In the past I have rarely seen SPECI not include all information, but things change all the time with no real consistency between countries.I'll have to think this one through.. There is no easy way I can think of - we'll need new "missing information" handling routines. Will put it on the list!Thanks again..


Damian Clark
HiFi  Simulation Technologies

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>In the past I have rarely seen>SPECI not include all information, but things change all the>time with no real consistency between countries.It may be more frequent than you think. Also, sadly you may even find that there is sometimes no consistency between reports from the same reporting station themselves. For example I have seen sets of SPECI reports for the same reporting station where sometimes they will include the altimeter setting and sometimes not.As for methods for trying to work around this, at the time of update you have the current (old) METAR/SPECI altimter setting in use and could temporarily store this and simply compare it with the altimeter value from the new METAR/SPECI data. If the new data does not contain an altimeter value instead of setting it to 29.92 as you currently do, just keep the previous value.


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Hi,Well it is a bit more involved than that... But thanks for the suggestions! And thanks for reporting this.-Damian


Damian Clark
HiFi  Simulation Technologies

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Guest hlm65

Hi Damian,I read of this SPECIs problem, but (unfortunately !!!) this is not the case for baro inconsistencies in offline mode (that we are privately discussing) if a valid (=complete) METAR was present for the destination airport.But maybe (if feasible) a sub-routine in AS that reads (compares) baro settings between 2 cycles (that is, even offline, to be able to check consistencies between 2 cycles) and looks for missing datas could be very useful.

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Guest Vidar

HiI have recently experienced a lot of instances when the altimeter setting showed in the "Active Radar" weather-tracking for the arrival airport is not being updated to FS. Instead I only get the standard barometric setting 1013 MB in FS. This causes me to have a completely wrong altitude on approach, if I rely on the "Active Radar"-tracker.I couldn't figure out what was causing this troubles, and reading this post, I'm glad to see I'm not the only one with this problem.Hope this will be fixed, as for the moment this is the only issue I have whatsoever with ActiveSky2004.5. I haven't regretted buying this software for one second. You guys are amazing, and you have managed to finally make the weather in FS realistic.

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Guest hlm65

Hi Vidar,it's some 2 weeks I'm getting inconsistent destination wx.I get perfeclty simulated departure and enroute weather and winds aloft, but when I get to my destination, even if the ATIS is right on the METAR/TAF, I get different visibility/clouds/winds and baro settings.I privately had a sereies of e-mails with Damian, but he seems unable to reproduce this problem.I fly offline with destination wx force and TAF enabled, AS2004.5 B163 and new FSUIPC.I checked and re-checked settings and addons that could be casuing conflict, but to no avail.Merry Christmas

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