Messages

Hi riju,
I'm interested if you succeed in vector map for flying. I was trying to create one with GPSBabel but finaly I found out there will be so many information with lot of overlayed airspaces (TMA, TSA, CTR ...) and locus have no ability to filter(turn on/off) layers and also navigation to point stored in .map is not possible (as far as I know) .So I end up with POI for airports and OpenAir files for airspaces (loaded/filtered through map item manager).  Also missing (or not found so far - i'm relatively new user) functionality to search for points in POI (or in .map when offline) I can only select them from map

@menion: would be possible in map item manager to let user to select more files and then confirm (at the moment after selection dialog closes immediately - it's not so comfort when you have 15 openair files)

just quick tested in my flat and seems fine, change in 1 milibar ~ change of 10 meters (approx), when weather get's better will check with airplane devices.

if anyone want calibrate (pressure based) you can use http://www.aviador.es/Airports/Nearby/ search any airport near you and in METAR (meteo report) find Qxxxx where xxxx is pressure at sea level e.g. Prague LKPR -  METAR LKPR 052130Z 26021KT 9999 BKN042 03/M02 Q0988 NOSIG= pressure is 988 hPa

Maybe another idea but not so important: mainly for hiking - to display height even when no gps fix available, can be good for someone in canyon or dense area. But for aviation it's not necessary as we shouldn't have any obstacle nearby ;-)

Big thanks, I'm also GIS developer and haven't seen anybody to react so fast on user requests ;-)

[3 values with 1 user input, 1 measured and 1 computed values]

Hi, I would like to post my opinion in this topic

Basically you have two options when using gps with barometric values,
1. automatic calibration (like garmin mentioned above)
2. manual - you have manully enter pressure at sea level or altitude

To get ideas you can check SportyPal software where it is already implemented. But I prefer manual setting where recalibration takes effect only when user wants. In hiking it is not changed too often as area and period where pressure changes are not too big. But in aviation terms, there are changes more common

Basically there are 3 values with 1 user input, 1 measured and 1 computed values
1. local pressure (measured value taken by sensor) (QFE in aviation terminology)
2. pressure at sea level (QNH)
3. altitude
(either 2. or 3. serve as an input the other one is then calculated)

In hiking most common approach is to set 3. as input then you are able to compute QNH (2) and then every change in pressure correspond to offset change in altitude. (e.g. suunto watches are using this method, altitude is taken from known points/landmarks etc)

In aviation most common approach is to set 2. as input then you are able to compute present altitude and then changes in pressure correspond to offset change in altitude ( QNH value is available in weather METAR messages for every airport or by tower when flying to different area - woudl be usefull to change during flight/track easily. Btw. flying above so called "transition altitude" (often 8000ft) requires all planes/glider to set QNH to 1013 - in aviation, pressure altitude ALWAYS takes precendence over GPS altitude, so manual setting would be welcome.

calculations can be taken from this page as resource http://www.hochwarth.com/misc/AviationCalculator.html (first part regarding QNH/QFE) or if exact equation is necessary let me know, but it is inside JavaScript on that page