Board index FlightGear Development Scenery

LIRN / Naples: Has ILS Z Rwy 06 incorrect 6° vs 3° offset?

Questions and discussion about enhancing and populating the FlightGear world.

LIRN / Naples: Has ILS Z Rwy 06 incorrect 6° vs 3° offset?

Postby ThomasV » Sat Dec 29, 2018 11:23 pm

Flightgear (and probably X-Plane) appears to have a runway 06 ILS set at 49° (for a 55° runway), resulting in approach offset that seems much greater than in reality.

In real life in 2007, LIRN's Rwy 06 ILS (NPC at 110.15 MHz) had a 3° offset at 53° (magnetic) whereas the 06 runway was at 56° (magnetic) in a region which had a 2°E magnetic variation in 2007 (J*pp*s*n LIRN chart).

In Flightgear, I notice that runway 06 is shown on FG's map at 55° corresponding, I suppose, to the 58.03° true heading provided in TerraSync/Airports/L/I/R/LIRN.threshold.xml
Notice that in Debug/environment/magnetic-variation-deg = 3.4168 (which is probably correct although the 40,000 km3 of magma below Naples confer a magnetic anomaly to Naples, helping make it a very attractive city to visit in real life :) ).

Flightgear's Naples NPC ILS is listed in Navaids/nav.dat.gz with 52.736° which, I suppose after subtracting the magnetic variation, provides the 49° value indicated on the map. The offset from runway 06, instead of being 3° is 6°.

Where does the 52.736° value come from? I have the impression that someone entered an magnetic heading (close to 53°) into the Navaid database instead of entering a true heading that should be about 58.03° (runway 06 true headng) minus 3° = 55.03°.

What do you think?
ThomasV
 
Posts: 2
Joined: Sun Dec 23, 2018 1:16 pm

Re: LIRN / Naples: Has ILS Z Rwy 06 incorrect 6° vs 3° offse

Postby FlyingGriffin » Mon Dec 31, 2018 2:37 pm

Hi there!
By simply taking a look at the map while flying on Capodichino airport (Naples airport) it is clear the ILS heading is wrong and evidently off from runway center line. This certainly needs to be fixed.
FlyingGriffin
 
Posts: 42
Joined: Tue Dec 25, 2018 7:04 pm
Location: Perugia, Italy
Callsign: IK0TOJ
Version: 2018.3.1
OS: Linux Fedora FC29

Re: LIRN / Naples: Has ILS Z Rwy 06 incorrect 6° vs 3° offse

Postby ThomasV » Sat Jan 05, 2019 12:30 pm

Thanks, FlyingGriffin, for your comment.
I posted a bug report to https://gateway.x-plane.com/bug/XSG-6756

Here's how to temporarily fix it in Flightgear (until the next update):
1) Take your plane to Naples, Italy. For example, Location: LIRN.
2) Exit Flightgear
3) In your user directory (in Linux: /home/username/.fgfs), delete navdata_2018_3.cache
4) Edit /usr/share/games/flightgear/Navaids/nav.dat.gz
cd /usr/share/games/flightgear/Navaids/
sudo gunzip nav.dat.gz
sudo gedit nav.dat
find LIRN and replace 52.736 NPC LIRN 06
with 55.030 NPC LIRN 06
sudo gzip nav.dat
5) Edit /home/username/.fgfs/TerraSync/Airports/L/I/R/LIRN.ils.xml
replace <hdg-deg>52.74</hdg-deg>
with <hdg-deg>55.03</hdg-deg>
6) Restart Flightgear
7) Verify on map.
Open the map (ctrl-j). Click on the [X] Data box at upper left. Slide map towards the right and verify that the ILS radial indicates:
NPC
LIRN 06 ILS-cat-I
052 - 110.15MHz
ThomasV
 
Posts: 2
Joined: Sun Dec 23, 2018 1:16 pm

Re: LIRN / Naples: Has ILS Z Rwy 06 incorrect 6° vs 3° offse

Postby wkitty42 » Sat Jan 05, 2019 1:41 pm

ThomasV wrote in Sat Jan 05, 2019 12:30 pm:3) In your user directory (in Linux: /home/username/.fgfs), delete navdata_2018_3.cache

you should not have to do this step... FG will automatically rebuild this file at startup when it detects the data it contains is not up to date with the data in the .dat files... it should easily detect these changes you made...

it is possible, too, though, that these changes can be done as overrides and no editing of the original files is needed... i'm not sure... what i speak of is in your local additional/custom scenery path, you can create a directory NavData... in there the directory "apt"... inside NavData/apt/ you put small files with your modified airport definition... they will override the entries in the default apt.dat... but i see this change is in nav.dat... i don't know if these would be read from a "nav" directory like the "apt" one... if it doesn't at this time, it should be fairly easy to add since this type of correction/addition is what it is intended for...

EDIT: i've just asked about this on the dev mailing list ;)
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
User avatar
wkitty42
 
Posts: 4949
Joined: Fri Feb 20, 2015 3:46 pm
Location: central NC, USA
Callsign: wk42
Version: git next
OS: Kubuntu 14.04.5

Re: LIRN / Naples: Has ILS Z Rwy 06 incorrect 6° vs 3° offse

Postby wkitty42 » Mon Jan 07, 2019 9:09 pm

i got a response back form the mailing list and yes, my statement above is correct... we should not be editing the default *.dat.gz files and we can fix/override some of them as i described... i have just tested this and it appears to work as desired...

Code: Select all
    0.00 [INFO]:general    FlightGear:  Version 2018.4.0
    0.00 [INFO]:general    FlightGear:  Build Type Dev
    0.00 [INFO]:general    Built with GNU C++ version 4.8
    0.00 [INFO]:general    Jenkins number/ID 0:none
    0.11 [WARN]:gui        Failed to load default (en) translations
    0.14 [INFO]:navaid     NavCache at:Path "/home/myuser/.fgfs/navdata_2018_4.cache"
    0.15 [INFO]:navaid     NavCache read-only flags is:0
    0.15 [WARN]:navaid     NavCache: rebuild required because '/home/myuser/flightgear-dev/fgdata-ng/Navaids/nav.dat.gz' (in cache) != '/home/myuser/myflightgear/mySceneryOverrides/NavData/nav/LIRN.dat' (on disk)
    0.15 [INFO]:navaid     NavCache: main cache rebuild required
    0.26 [INFO]:navaid     NavCache at:Path "/home/myuser/.fgfs/navdata_2018_4.cache"
    0.26 [INFO]:navaid     NavCache read-only flags is:0
    0.26 [INFO]:navaid     will create tables
    4.64 [INFO]:general    Loading apt.dat file: '/home/myuser/myflightgear/mySceneryOverrides/NavData/apt/5B2.dat'
    4.64 [INFO]:general    apt.dat format version (/home/myuser/myflightgear/mySceneryOverrides/NavData/apt/5B2.dat): 1000
    4.64 [INFO]:general    Loading apt.dat file: '/home/myuser/myflightgear/mySceneryOverrides/NavData/apt/CCC5.dat'
    4.64 [INFO]:general    apt.dat format version (/home/myuser/myflightgear/mySceneryOverrides/NavData/apt/CCC5.dat): 1000
    4.64 [INFO]:general    Loading apt.dat file: '/home/myuser/myflightgear/mySceneryOverrides/NavData/apt/ZBAA.dat'
    4.64 [INFO]:general    apt.dat format version (/home/myuser/myflightgear/mySceneryOverrides/NavData/apt/ZBAA.dat): 1000
    4.65 [INFO]:general    Loading apt.dat file: '/home/myuser/flightgear-dev/fgdata-ng/Airports/apt.dat.gz'
    4.65 [INFO]:general    apt.dat format version (/home/myuser/flightgear-dev/fgdata-ng/Airports/apt.dat.gz): 1000
    5.09 [INFO]:general    /home/myuser/flightgear-dev/fgdata-ng/Airports/apt.dat.gz:387533: skipping airport ZBAA (already defined earlier)
    5.68 [INFO]:general    /home/myuser/flightgear-dev/fgdata-ng/Airports/apt.dat.gz:926125: skipping airport CCC5 (already defined earlier)
    6.83 [INFO]:general    /home/myuser/flightgear-dev/fgdata-ng/Airports/apt.dat.gz:1961600: skipping airport 5B2 (already defined earlier)
    7.41 [INFO]:navaid     apt.dat files load took: 2769
   20.17 [INFO]:general    Loaded data for 34074 airports
   20.17 [INFO]:navaid     processing airports took:12761
   20.21 [INFO]:general    Loading fix.dat file: '/home/myuser/flightgear-dev/fgdata-ng/Navaids/fix.dat.gz'
[...]
   26.08 [INFO]:navaid     fix.dat files load took: 5868
   26.08 [INFO]:general    Loading nav.dat file: '/home/myuser/myflightgear/mySceneryOverrides/NavData/nav/LIRN.dat'
   26.08 [INFO]:general    Loading nav.dat file: '/home/myuser/flightgear-dev/fgdata-ng/Navaids/nav.dat.gz'
[...]
   28.47 [INFO]:navaid     /home/myuser/flightgear-dev/fgdata-ng/Navaids/nav.dat.gz:13004: skipping navaid 'LIRN 06 ILS-cat-I' (already defined nearby)
[...]
   31.17 [INFO]:navaid     nav.dat files load took: 5085
   31.77 [INFO]:navaid     stage 1 commit took:597
   62.43 [INFO]:navaid     poi.dat load took:30225
   64.01 [INFO]:navaid     POI commit took:1576
   70.29 [INFO]:navaid     awy.dat load took:6280
   71.52 [INFO]:navaid     final commit took:1231
   71.52 [INFO]:navaid     cache rebuild took:71302msec



my NavData/nav/LIRN.dat file contains these lines...
Code: Select all

810 Version - data cycle 2013.10, build 20131334, metadata NavXP810.  Copyright (c) 2013, Robin A. Peel (robin@x-plane.com).   This data is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.  This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.  You should have received a copy of the GNU General Public License along with this program ("AptNavGNULicence.txt"); if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.

4  40.88688900  014.28988900    294 11015  18      52.736 NPC  LIRN 06  ILS-cat-I



i just copied the whole first line from the nav.dat.gz file and pasted it in so it would properly conform to the nav.dat format... then i put in the one line that needed to be changed and off we went :)
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
User avatar
wkitty42
 
Posts: 4949
Joined: Fri Feb 20, 2015 3:46 pm
Location: central NC, USA
Callsign: wk42
Version: git next
OS: Kubuntu 14.04.5


Return to Scenery

Who is online

Users browsing this forum: No registered users and 3 guests