What does "override upper altitude" checkbox do?

[bvl]

Hi there,

yesterday i went flying in Lihue, Hawaiian Islands.

When i was on the runway, visibility was around 5nm.

Then i took off, and around 500-1000 feet above ground, the visibility suddenly changed to at least 30-40nm. So, looking back to the airport, i saw the airport clear as if the visibility on the ground would be very high.

This is especially irritating when approaching: Clear view onto the runway, and when descending into a low-visibility layer, the visibility suddenly decreases and i cannot see the runway anymore.

I use the "visibility smoothing" feature, but this does not really cure the problem that i can SEE the airport from high above, but CANNOT SEE the terminal building 50 meters in front of me when i am on the ground.

Is there any solution? Is ist a fs2004 bug? Is it my fault (wrong configuration?).

Another thing that could have something to do with it: What does the "override upper altitude" checkbox and the corresponding value do exactly? And what if i set this value to 0? And what if i set this value higher than 0?

Thanks in advance

Bodo

[Pete Dowson]

When i was on the runway, visibility was around 5nm.

Then i took off, and around 500-1000 feet above ground, the visibility suddenly changed to at least 30-40nm. So, looking back to the airport, i saw the airport clear as if the visibility on the ground would be very high.

I don't know what weather you are using. The default FS2004 visibility layer isn't very deep, and when you fly above it you normally will get the default "unlimited" value. In FS2004 they did add a sort of thin cloud graphic to the top of the visibility layer, but I think that can look odd too. Some of the replacement cloud textures available change that or even may remove it.

This is especially irritating when approaching: Clear view onto the runway, and when descending into a low-visibility layer, the visibility suddenly decreases and i cannot see the runway anymore.

I use the "visibility smoothing" feature, but this does not really cure the problem that i can SEE the airport from high above, but CANNOT SEE the terminal building 50 meters in front of me when i am on the ground.

But is should fix the sudden changes. It certainly does here.

Is there any solution?

Turn on the FSUIPC graduated visibility option. Use that in conjunction with the FSUIPC visibility maxima and the smoothing.

Another thing that could have something to do with it: What does the "override upper altitude" checkbox and the corresponding value do exactly? And what if i set this value to 0? And what if i set this value higher than 0?

It does nothing at all unless you are getting weather inserted from an external weather program, or you are forcing Global weather only at intervals in FS and have the FSUIPC technical option enabled to make FSUIPC fiddle with FS global weather. In those cases it overwrites the upper altitude set for the surface visibility layer with the value you put there. You might do that to set a higher value than the one being set by the weather program. I can't see why you'd ever want it lower, but you might if a weather program set fog up to 30000 feet! :)

Your best bet is to enable all three options marked *** on the FSUIPC visibility page.

Regards,

Pete

[bvl]

Hi,

thanks for the quick reply. I already have all three options (graduate visibility, visibility maxima and override upper altitude) activated. I am using fs9 downloaded weather.

The visibility layer is NOT visible from above and therefore microsoft build a thin cloud (visible from above) to the top of the visibility layer to make the problem less severe. But i will NOT see the fog until i am in the visibility layer. I will ONLY see this thin cloud.

Did i understand this correctly?

[Pete Dowson]

The visibility layer is NOT visible from above and therefore microsoft build a thin cloud (visible from above) to the top of the visibility layer to make the problem less severe. But i will NOT see the fog until i am in the visibility layer. I will ONLY see this thin cloud.

Did I understand this correctly?

Well, yes, sort of -- but the "thin cloud" is supposed to look like the mist/fog covering the ground. Many folks don't like the effect at all, so I'm surprised you appear to not even see it. Replacement cloud textures may affect it.

The graduating visibility that FSUIPC can apply should keep you in a diminishing fog in any case as you ascend. Perhaps you have one of the altitudes set wrong for that? Set the lower altitude to 0 to have it starting at the top of the FS layer.

Pete

[bvl]

Yes, i have replacement textures, and i can indeed see this thin cloud layer you talked about. It's there, but it's very transparent.

The graduate visibility features low altitude is set to 0 and going up to max visibility of 70 miles in 25000 feet.

But the graduation does not begin with the visibility in the fog layer, it begins with the visibility i set as the max. visibility values.

Let's assume the fog layer is from 0 to 2000 ft AGL, with a visibility of 1 mile. and let's further assume that the sky is cloudy and the max visibility in cloudy conditions is set to 20 miles. The max graduated visibility is, lets say 40 miles in 22000 feet (for easier calculation) Then i get the following:

ALTITUDE | VISIBILITY | CAN SEE GROUND CLEARLY

-------------+-----------------+-----------------------------------

100ft 2 nm no, only in heavy fog

1900ft 2 nm no, only in heavy fog

2100ft 20 nm yes nearly (thin nearly transparent cloud)

12000ft 30 nm yes nearly (thin nearly transparent cloud)

22000ft 40 nm yes nearly (thin nearly transparent cloud)

So the cloud layer seems to be too thin or it is indeed a problem of the cloud texture. I will try the original textures again and see...

Thanks for your time

Bodo

[Pete Dowson]

Yes, i have replacement textures, and i can indeed see this thin cloud layer you talked about. It's there, but it's very transparent.

Yes, I think it is supposed to be. It doesn't appear to depend on the actual surface visibility, which is not good. It does change a bit when the cloud textures are replaced, but whether for the better or worse I can't really say.

I ignore it by flying the aircraft and looking where I'm going, not where I've been! :)

But the graduation does not begin with the visibility in the fog layer, it begins with the visibility i set as the max. visibility values.

Let's assume the fog layer is from 0 to 2000 ft AGL, with a visibility of 1 mile. and let's further assume that the sky is cloudy and the max visibility in cloudy conditions is set to 20 miles. The max graduated visibility is, lets say 40 miles in 22000 feet (for easier calculation) Then i get the following:

ALTITUDE | VISIBILITY | CAN SEE GROUND CLEARLY

-------------+-----------------+-----------------------------------

100ft 2 nm no, only in heavy fog

1900ft 2 nm no, only in heavy fog

2100ft 20 nm yes nearly (thin nearly transparent cloud)

That's correct for FSUIPC because it should be smoothing the change between the 2 nm and the 20 nm. Try setting the rate of change of the smoothing to be a lot slower. You need to adjust things till you are happy. Try setting a lower maximum too. With the FS upper fog altitude being so low (2000 feet), lower limits suit things better, at least in Europe. In some parts of the world this wouldn't be so good.

But on the transparency issue, you are right. Not only with fog, but clouds generally, Folks complain that even with lots of cloud you can see through them when above. And overcasts aren't!

I actually get annoyed by seeing runways (only) as black bars straight through poor visibility and clouds, but I'm not sure whether this is only for my add-on airports or defaults. Maybe the add-ons (UK2000) are not defined in a way which allows them to disappear behind clouds. I've not seen any one else mention this phenomenon.

FS2000 was, in my opinion, the best version so far for good visibility effects. The clouds weren't as good as in FS2004, but the visibility issues were all sorted. FS2002 was a complete disaster in that area, and FS2004 has recovered somewhat -- looking quite good sometimes -- but there's still some way to go.

Regards,

Pete

[ronzie]

This type of discussion is very frequent especially on the Active Sky forum at

http://forums.avsim.com/dcboard.php?az=&forum=171

What the programmers there do for FS9 is to have two close cloud layers generated to give a denser appearance from above. They are still working on it in AS2004.

Also, be sure your 3D cloud density is set to max and see if that helps if you can withstand the FPS load.

[bvl]

Hi,

good idea with this 2 cloud layers. Could this possibly be achieved with an addition to the code of fsuipc? Of course, fsuipc is not a weather generation tool and there could be implementation problems, but i like the idea!

[Pete Dowson]

good idea with this 2 cloud layers. Could this possibly be achieved with an addition to the code of fsuipc? Of course, fsuipc is not a weather generation tool and there could be implementation problems, but i like the idea!

It's done (optionally) already by ActiveSky. But it does tend to hit frame rates rather hard.

Pete

[bvl]

But it does tend to hit frame rates rather hard.

Ok, i like the visibility rendition of fs2004 very much just as it is ;-)