Altitude irregularities

[vdkeybus]

Hello everyone,

I have connected a dial type altimeter to FS. I'm achieving update rates from FS to the instrument of over 60 per second (it being the only instrument that gets updated). I noticed that the altitude is not changing smoothly on the instrument, but seems to 'jerk' a little. It looks as if the FS altitude is internally updated only 2 times per second and then filtered to get smooth values in the panel.

Has anyone seen this behaviour and is there a cure for it ?

I'm using FS2002, locked at 30 Hz frame rate. The FSUIPC memory location I read is 0x3324 (barometric altitude).

J.

[Pete Dowson]

It looks as if the FS altitude is internally updated only 2 times per second and then filtered to get smooth values in the panelI'm using FS2002, locked at 30 Hz frame rate. The FSUIPC memory location I read is 0x3324 (barometric altitude).

It isn't FS, it is the way FSUIPC obtains that value. It is read from PANELS.DLL using normal panel accesses. Since these are relatively slow (involving lots of nested procedure calls and, in this case, computations at the end of it too), they are done infrequently -- only twice per second, which is exactly what you are seeing.

This didn't particularly worry me because most of the values I have to read this way don't need faster updates in any case. This is obviously an exception when used directly for instrumentation -- in fact as far as I can see it is the only exception in that particular list.

Sorry about this. Evidently it hasn't been a problem before. This value was a late addition to the interface, and pretty much all users did it the "harder" way -- reading the aircraft altitude and correcting this for the difference between QNH and the Altimeter setting. Since the aircraft altitude value is a direct read from an FS-maintained location, not an artificial value from FSUIPC, it is much more responsive.

I will change the polling rate for this to match the frame rate. Just the one value so read shouldn't affect performance noticeably -- in everything I do in FSUIPC, zero measurable effect on performance has always been a prime goal.

This change will be in FSUIPC version 3.20, which I am planning to release this weekend.

Regards,

Pete

[vdkeybus]

Hi Pete,

I will change the polling rate for this to match the frame rate. Just the one value

I feel very much obliged. Thanks.

J.