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D-ECHO Caribbean scenery edit?

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Re: D-ECHO Caribbean scenery edit?

Postby wkitty42 » Sat Jul 06, 2019 3:35 pm

D-ECHO wrote in Sat Jul 06, 2019 1:49 pm:Yes, genapts850 uses the --max-slope parameter with --max-slope=0 being a completely flat airport and --max-slope=1 being an airport that *can*, if the hgt data demands it, have slopes up to 45° (100%=1). At least that is how I understand it. This occurs within the airport boundaries, as BecOzIcan mentioned, with genapts producing a cliff at the boundaries if the normal terrain elevation does not equal the airport element's elevation there

if one really wants to see how --max-slope works, generate the area around XBEL in hawaii... the now un-used runway there is pretty steep... it rises going from inland to the ocean... the current load in FG chops the hill and places the runway in a canyon that doesn't exist in RL...
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Re: D-ECHO Caribbean scenery edit?

Postby SurferTim » Sat Jul 06, 2019 3:44 pm

The QGIS editor is a level above where I am right now. I can access the 16 bit elevation in meters of each individual 90 meter "square" of real estate.

My question is: Is it worth it to be able to edit the hgt files with a Python script designed pretty much for Flightgear? Or am I reinventing the wheel?

@wkitty42: I experience the same thing here with TFFS in the stock scenery. It is in a ravine that shouldn't be there.
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Re: D-ECHO Caribbean scenery edit?

Postby SurferTim » Sun Jul 07, 2019 12:55 pm

I used your scenery again today. I like it except some of the runways, especially St Barth.

The way I see it, there are three choices.
1) leave it like it is, which is not correct. Not enough cliff, too much runway gradient.
2) lie to the scenery compiler.
3) "bulldoze" the airport property in the hgt file with an external app.

Before I put a lot of effort into #3, may I suggest we try #2. You say you use the --max-slope parameter, so maybe cut that value in half.

What you should be looking for is a 42 to 45 foot difference between the rwy12 threshold and the rwy30 threshold. See if it is possible to adjust --max-slope to get that.

Then adjust the airport elevation to get the rwy30 threshold at somewhere around 3 to 6 feet. That should put the rwy12 threshold at about 48 feet.

If that doesn't work, I'll continue to work on the "bulldozer" app.
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Re: D-ECHO Caribbean scenery edit?

Postby D-ECHO » Sun Jul 07, 2019 2:13 pm

According to http://dc-ansp.org/eAIS/SUP/AIRAC%20AIP ... 0Chart.pdf the runway ends (not thresholds) have an elevation difference of 138-111=27ft with a distance of 1317ft meaning a slope of 27/1317=0.021. I will try how it looks like when I put this into genapts as "max slope". Please note though that changing the airport elevation in WED has AFAIK absolutely no effect on the generated airport's elevation, it only affects the tower view.
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Re: D-ECHO Caribbean scenery edit?

Postby SurferTim » Sun Jul 07, 2019 2:27 pm

That is interesting. So if you change the --max-slope, where will it put the cliffs? What elevation does it use as the base line? How is that elevation determined?

Edit: SkyVector shows TFFJ elevation as 48 feet on rwy10 and 4 feet on rwy28.
https://skyvector.com/airport/TFFJ/St-B ... my-Airport

Edit2: My bad. I thought we were discussing St Batrth (TFFJ).
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Re: D-ECHO Caribbean scenery edit?

Postby D-ECHO » Sun Jul 07, 2019 3:01 pm

IIRC, the elevation is determined based on some kind of median elevation of the airport area from the .hgt file
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Re: D-ECHO Caribbean scenery edit?

Postby D-ECHO » Sun Jul 07, 2019 3:03 pm

Using the slope determined above I get elevations of about 31m to 33m (pushed for tests)
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Re: D-ECHO Caribbean scenery edit?

Postby SurferTim » Sun Jul 07, 2019 3:05 pm

D-ECHO wrote in Sun Jul 07, 2019 3:03 pm:Using the slope determined above I get elevations of about 31m to 33m (pushed for tests)

Where? If at Saba, it is ok for now. I was discussing St Barth TFFJ.
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Re: D-ECHO Caribbean scenery edit?

Postby D-ECHO » Sun Jul 07, 2019 3:13 pm

ups okay. TFFJ is quite a different beast as I also tried to make the "step" in front of the threshold as small as possible (no step in real life).
Here we have 48-4=44ft difference over a length of 2119ft so a slope of 44/2119=0.021 for the runway. This leads to a step like this:
Image
I'd leave it up to the pilots to decide: is this acceptable or too much?
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Re: D-ECHO Caribbean scenery edit?

Postby SurferTim » Sun Jul 07, 2019 3:17 pm

Not too much. I think not enough. Have you seen St Barth? There are a bunch of YouTube videos of the airport there.

The threshold elevation on that end of the runway should be 48 feet (15 meters).
On the other (bay) end, the threshold should be 4 feet (1 meter).
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Re: D-ECHO Caribbean scenery edit?

Postby D-ECHO » Sun Jul 07, 2019 3:20 pm

As told, I can not set the elevation manually, the threshold is at ~21m instead of ~15m now. Also note that I am talking about the *step* not the *slope*. In a perfect world (and in the real world), there is a rather even slope from the street down to the threshold, but as the tools are as they are, we will always have at first a too shallow slope and afterwards a rather hard cut, or as I called it, step.
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Re: D-ECHO Caribbean scenery edit?

Postby SurferTim » Sun Jul 07, 2019 3:26 pm

Take it down to 48 feet (15 meters). If there is a "step" and a "slope", so be it. Let's see it. I might be able to patch the step into the slope.

How does it look on the other end? Around 4 feet? 1 meter?
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Re: D-ECHO Caribbean scenery edit?

Postby D-ECHO » Sun Jul 07, 2019 3:29 pm

SurferTim wrote in Sun Jul 07, 2019 3:26 pm:Take it down to 48 feet (15 meters).

This is not possible. There is no way to manually set the elevation without changing the .hgt or .bgt files. The slope is now correct as is, everything else would have to be by manually editing the input or output data.
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Re: D-ECHO Caribbean scenery edit?

Postby D-ECHO » Sun Jul 07, 2019 3:30 pm

Around 10m vs 1m at the other end
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Re: D-ECHO Caribbean scenery edit?

Postby SurferTim » Sun Jul 07, 2019 3:35 pm

D-ECHO wrote in Sun Jul 07, 2019 3:30 pm:Around 10m vs 1m at the other end

Not good. :(

How is it not possible to adjust the median elevation of an airport? In the stock scenery, the runway at Les Saintes TFFS is in a ravine cut through a hill. How did they do that?

Edit: I guess this means "bulldozer" if the elevation and the slope cannot be adjusted sufficiently.
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