Altitude and Vertical Velocity Unit Scaling

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Scotflieger
Airman
Posts: 11
Joined: 23 Dec 2015, 17:07
Location: Buckie, Scotland, UK

Altitude and Vertical Velocity Unit Scaling

Post by Scotflieger »

I am the support developer for the core LINDA freeware for simply defining joystick buttons definitions. I have found an interesting issue with the FSUIPC4 offsets for Autopilot Altitude (07D4) and Vertical Velocity (07F2) with A2A aircraft add ons in FSX and P3D. I have checked with Pete Dowson regarding the definitions for both simulators.

The offsets are:
07D4 4 bytes Autopilot altitude value, as metres*65536
07F2 2 bytes Autopilot vertical speed value, as ft/min

​The altitude is quoted as being in metres and the vertical speed in ft/min.

​I have found through detailed tests that the conversion of Altitude from metres to feet is required only if the A2A A182 or C172 aircraft are used or when using P3D (alt = round(0x07D4 * 3.2808399 / 65536)). The reverse applies to the Vertical Speed. If not A2A or P3D, VS= round(0x07F2 / 3.2808399).

In all other cases (FSX and non-A2A), the offsets are defined as AP Alt in feet and AP VS in metres/sec. This is opposite from the FSUIPC4 Status of IPC Offsets for FSX document.

Can A2A confirm which units are used for C172, A182 and other A2A add ons?

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some1 - A2A
A2A Lieutenant Colonel
Posts: 1828
Joined: 03 Aug 2008, 11:56

Re: Altitude and Vertical Velocity Unit Scaling

Post by some1 - A2A »

Hello,

we don't use FSUIPC and offsets, we use simconnect and FSX(P3D) simulation variables directly.
I've no idea why you see different results on two simulators, the code is the same on both platforms and it operates on Imperial units. Maybe the regional settings are different between the simulators on your PC?
Michael Krawczyk

Scotflieger
Airman
Posts: 11
Joined: 23 Dec 2015, 17:07
Location: Buckie, Scotland, UK

Re: Altitude and Vertical Velocity Unit Scaling

Post by Scotflieger »

Thank you for the prompt response. The use of imperial is the key point and the answer I was looking for. The PC regional settings has no impact on the flight simulators.

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