Altitude setting

GeoffS

GeoffS

Member
I use the Nav guides display just showing air speed, wind speed, and altitude. Whichever altitude choice I make (AGL, ASL, ATL) it shows 11 metres when the model is on the runway when it should be zero (except for ASL, I suppose). When flying, the altitude changes OK but always 11 metres (35') too high.

Is there a calibration I'm missing somewhere?

Geoff
 
GeoffS said:
I use the Nav guides display just showing air speed, wind speed, and altitude. Whichever altitude choice I make (AGL, ASL, ATL) it shows 11 metres when the model is on the runway when it should be zero (except for ASL, I suppose). When flying, the altitude changes OK but always 11 metres (35') too high.
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What does your heads-up display show? ( keyboard 9 )

You might try "Restoring Defaults" ; however, I think its probably related to your having recently deleting Rf and installing Rf9.5.031 and having something interfering between the two installs. (maybe run it by HH service)

marcus
 
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The HU display is correct, ie showing 0 metres when the aircraft is on the runway. Setting the Nav Guide defaults doesn't affect the altitude error. Odd.

It's possible there is some interaction between the old and new installations but unlikely, I think. I cleared all the files both by performing a proper uninstall and deleting any remnants I found. I do have a file with a few extra aircraft files (not installed in RF but downloaded from the 'swap' area). I can't see that affecting altitude but strange things happen with s/w.

Geoff
 
The altitude error only seems to apply to AMA flying site 3. It's OK at Sods Farm (really? :) ), Eli Field and Carl Henson field (the few I've tried). It's not a serious problem but perhaps it's something to do with the coding for that site?

Geoff
 
GeoffS said:
Ah, so it's not only me
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Select the "AMA Flying Site 3" and then, under Environment, select "edit". In the objects list find the "AMA Site 3 Asphalt" and then in the "Properties," "Parameters," "Relative Position(m)"... you'll notice that the "Z" component is set to 11.821

Change that value to 0.221, and then exit|save... you will need to rename it "AMA Flying Site 3_2" ; the ASL AGL should now be zero "0" with the aircraft sitting on the runway. You'll notice your aircraft is lower too... by about 11 meters... its fairly dramatic.

This is not a solution... just wanted you to see where the number comes from. The Z component of the Asphalt is "off" because the rest of the field is "off" as well... this field isn't built very well, unfortunately. To make everything right you would have to go through all of the Z components, of all the objects relative to the asphalt, and set them correctly too... including the height of the pilot observer. I really don't think its worth the effort, but it might be a fun exercise.

PS for instance, the flight line chain-link fence barricades are "floating" in the air with the asphalt 11 meters lower. So, the flight line fences would need to be lowered as well; everything actually... like the grass surrounding the asphalt!


marcus
 
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I use an edited version of that site anyway because, as I've said elsewhere, I like to see the windsock adjacent to the runway so I can set a known wind direction more easily. OK I hit it occasionally but so what? :)

I don't think I'll bother editing the whole airfield unless there's a global Z edit, perhaps? But it is interesting to see where the error arises. Thanks for highlighting it. It seems strange no-one's noticed it before. My favourite manoeuvres are touch and goes and that site is great for that. I find the runways on other sites very narrow because the 3D is lacking.


Geoff
 
GeoffS said:
My favorite maneuvers are touch and goes and that site is great for that. I find the runways on other sites very narrow because the 3D is lacking.
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The best touch and go site is Evergreen... you stand right next to the Windsock, so you don't hit it.

Evergreen is paved forever, and is quite wide... also, wide open space; color and light are good, its great.

PS also, the photo-field is visually "clear" and crisp.

marcus
 
Thanks, I'll give it a try.

Unfortunately, we're losing our site in the UK. It's a former WW2 airfield that's slated to become a huge housing estate. We have lots of Tarmac as well as a sizeable grass area. We're moving somewhere lower, with less wind but all grass that will probably be soggy in winter. If the RF model sites are a fair representation of the reality I'm officially envious :)

Geoff
 
GeoffS said:
We're moving somewhere lower, with less wind but all grass that will probably be soggy in winter. If the RF model sites are a fair representation of the reality I'm officially envious
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Our home field is all closely mowed grass; often soggy, and usually unusable for models with small wheels, like the Apprentice STS, any of the EDF Jets, etc. The giant scale planes like my CarbonZ Cub SS 2.1m, or Turbo Timber 1.5m, have very large bush style wheels, so grass fields are fine; although, I did have the tail wheel of my Timber catch on a weedy thing and tear the wheel off! (easy repair)
I've been prompting our homies to build a runway, but they keep telling me it ain't gonna happen any time soon.

marcus
 
Well I'm currently building a semi-scale Li'l Cub which won the Valdez STOL competition recently from a free plan published in RCME mag, June 2019. It will have quite large wheels so it'll be well suited to our new site as well as casual flying from a local pasture near our house (sheep occupancy depending).

Incidentally, I tried adjusting Z at AMA Flying Site 3. Quite amusing effect - it made the model appear extra small for some reason. I won't persist with the change. RF is an entertaining program to play with in lockdown now I've at last got it to install properly

Geoff
 
GeoffS said:
Incidentally, I tried adjusting Z at AMA Flying Site 3. Quite amusing effect - it made the model appear extra small for some reason.
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The reason is that the observer (pilot, you) are still at the same Z, and the asphalt runway is now (11) meters 'down'. So, its like you are 11 meters in the air looking down at your very tiny model way down there... so, yeah, to fix that field we have to go through the entire layout and adjust everything (including the pilot observer) to be at ground level.

marcus
 
I've just noticed that this airfield is featured on the box for my s/w only version of RF. You'd have thought they'd make sure it was properly programmed if they feel it was worth advertising on the packaging.

Must admit I never thought about adjusting 'my' Z value but that's obviously the reason the model looked small. All good fun.

Geoff
 
In reality, this PhotoField is probably our best built and most accurate one yet! I can certainly understand the confusion above, however.

I'll explain.

PhotoFields are all located in a "world" that is a perfect flat plane. You never see that because visually it's covered up by the panorama. But the underlying terrain is entirely flat in all directions.

"Level" ground in the real world is anything but. There are pretty much always at least minor changes in elevation over larger distances. The amount of variation often ends up being quite surprising compared to what our eyes perceive. And it turns out that even small changes end up wreaking havoc with panoramic images. Also, aside from whatever elevation changes and unevenness may be present in the scene, the panoramic image itself is likely to have some bowl distortion, even if it is well made (and possibly other issues if it is not). When the model gets far enough away, it will either seem to penetrate the ground or be floating above it even though it is taxiing happily, or things will appear too large for their actual distance. All kinds of fun things can happen! ;)

In cases where the terrain elevation changes much at all, and/or when there are grass berms or other similar features, we compensate using invisible 3D objects to match that shape. Then the RC model generally interacts with the world as it should. It's quite similar to how we use invisible 3D objects matching the shape of other objects in the scene like tables or buildings so that you can collide with or even fly behind and under them.

In the past we have very carefully constructed those kinds of terrain objects by hand. It takes a lot of work. AMA Flying Site 3 is the first to use a new, vastly superior technique. We used a detailed drone scan of the site to capture every detail and then constructed 3D terrain objects from that data. It allows us to represent the site with far greater fidelity and nuance. There are numerous advantages, such as the ability to better account for the kinds of elevation changes I mentioned above and to keep things looking correct farther away from the camera.

(We have an unreleased test PhotoField of our local flying field created using this technology, and the way it reproduces the "bump" an airplane makes when transitioning from the slanted taxiway onto the more level runway is uncanny. It really tricks the brain into thinking you're there!)

The only problem is the one you encountered: when the aircraft is resting on an object that represents "terrain", the altitude displays do not take that into account. This results in reported altitude values that are quite inexplicable until you understand what's going on. (Incidentally, you can see the same issue but to a much lesser degree at LIARS Field, where the earlier, more rudimentary version of this technique had to be employed.)

I have filed a case in our bug-tracking system to look into the best way to compensate for that. Thanks for bringing it to our attention.
 
I look forward to your update. I use this field in preference to all the others (at least for now). Now I'm aware of the altitude issue, it isn't a problem. I was merely puzzled and wondered if there was a way of calibration I hadn't noticed. What I did notice was the little bump as I taxied from the grass to the Tarmac and vice versa which, as you say, is quite neat.

One thing I would like is a means of relating wind direction to the simulated terrain. I think just increasing wind strength (via 'Page Up') from the default starting position automatically increases it as a headwind but I'm not sure. I've had the Phoenix sim for several years and there's an option to show wind relative the aircraft's position which is handy. After all in what passes for real life I can feel the wind - when on my PC it's not so easy :)
 
I have created through trial and error a photofield of our local field, it will need some altitude tweaking for the distant surrounding field but that is usable for now. My problem is the proportion of the field to the airplane. The Valiant look about 3 X too large and the field to short. is there an adjustment for that or did I do something wrong in creating the panorama?
 
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