Auto QNH

We’ve already explained that there is a heck of a lot of new features in the recently released version of SeeYou Mobile version 6. We’d like to introduce some of them more closely in separate blog posts and this is the first one in the series.

Auto QNH is one of my favorites.

AutoQNHIt’s very simple to explain and equally effective. SeeYou Mobile will correct the current standard pressure altitude to the current altitude above sea level and calculate the current QNH pressure with that data.

So simple?

Yes. There are a few ways how to do that too and a few fallbacks if one method fails. Here’s what we will typically try to do:

1. Determine if there is an airfield nearby (takeoff in the paragliding version). We will use that altitude as the source for the QNH calculation.

2. Should an airport not be available close by we will use the ground elevation from the current location and use that.

3. If we determine that the ground is not level enough we will then fall back to a solution which is not scientific (at all) but still better than doing nothing. We will average the GPS altitude for a long time and then apply that altitude as the source for the QNH correction.

When is Auto QNH available?

It is available by default in the Oudie IGC and Oudie 3 which both have a very reliable and accurate pressure sensor already installed. On an Oudie 2 (and 1) where only GPS altitude is available internally you need some input from pressure sensors to be able to use Auto QNH. You get that if you connect your Oudie to an IGC approved flight recorder or vario such as Flarm, LXNAV V7, Nano, Colibri, CAI 302, Borgelt vario etc etc. The list is long and these are only the most popular solutions out there.