Computes the pick direction and starting point. This is code that translates
a screen coordinate into a vector in the FlightGear world (between the eye and
the on-screen coordinate.) Armed with this vector in FG world coordinates,
you could call a scenery intersection routine and lookup the lon/lat/elev of
the point in the world that was clicked on.
* in some cases more specific sg exception types were used in place
of the more generic one, e.g., sg_io_exception instead of sg_exception
when the context of the error was an IO error
* in some cases, the error message was made more specific
* minor style fix for exception rethrowing --- using throw; whenever
a re-throw is made; sometimes optimizing away the exception symbol name
in the catch handler at all
* more specific catch handlers added in some places -- e.g.,
an sg_io_exception caught ahead of sg_exception
Insert empty string as marker between FG_SCENERY path elements.
FG_SCENERY=A:B expands to [A/Terrain, A/Objects, "", B/Terrain, B/Objects, ""]
(assuming that both A/ and B/ have Terrain/ and Objects/ subdirs).
tileentry.cxx -- FGTileEntry::load():
Check all tile dirs in FG_SCENERY from left to right: add all objects
to the scenery until a terrain tile was found: In this case read the
rest of that group (i.e. the Objects/ twin dir) and then stop scanning.
Better structuring of log messages & fix warnings.
to pop themselves down while the simulator is paused.
The problem was with the "real time" queue in the event manager,
causing the third argument of Nasal's settimer() (a flag for "sim
time") to be ignored. Inverts the default sense of the argument, as
there are lots of uses of settimer() in the current code, almost none
of which want to use real time.
Note this fix introduces a header file incompatibility in SimGear --
be sure to update.
redraw(): redraw gui without distroying dialogs (fgcommand "gui-redaw"/Shift-F10)
This change makes sure that Nasal-generated and dynamic dialogs can be
re-opened correctly when cycling through themes.
there was the situation where four directories contained jst two files,
of which three directories were aircraft related, and one directory contained
test code from Curt that might be better of in SimGear anyhow.
This is just a patch to move a bunch of files to new locations. In case of
local changes to any of them you can do the following:
move replay.[ch]xx from src/Replay to src/Aircraft
move control.[ch]xx from src/Control to src/Aircraft
move ssgEntityArray.[ch]xx from src/Objects to simgear/screen
In addition it has been decided only to use .[ch]xx files in all directories
unless it's contained within an FDM specific directory, in which case the
author is free to do whatever (s)he wants.
In this repspect the following files have been renamed in src/Multiplayer:
tiny_xdr.[ch]pp has become tiny_xdr.[ch]xx
multiplaymgr.[ch]pp has become multiplaymgr.[ch]xx
* Use "const string&" rather than "string" in function calls when appropriate.
* Use "const Point3D&" instead of "Pint3D" in function calls when appropriate.
* Improved course calculation in calc_gc_course_dist()
* Safer thread handling code.
Vassilii Khachaturov:
Dont use "const Point3D&" for return types unless you're absolutely sure.
Erik Hofman:
* Use SGD_(2)PI(_[24]) as defined in simgear/constants.h rather than
calculating it by hand every time.
CygWin/gcc-3.4.4 updates.
I replaced my cygwin compiler with 3.4.4, did a make clean of plib, simgear,
and flightgear, then did a make install of all three. With the included changes,
everything builds fine, and runs fine.
I stumbled across two memory errors with two wrong const references to
std::string.
As I fixed that, I also moved aircraft_dir which is only used from UIUC into
UIUC. With that uiuc_aircraftdir.h is empty and can be removed.
I believe I have found the agl hud problems as well as the 'hole' in the
carrier's deck. I spent half the day to reproduce that problem, it did not
occure when you start on the carrier not does it occure with JSBSim and my
really often used testaircraft. So I really need to improove my helicopter
flying qualities.
I was under the impression that *all* FDM's call
FGInterface::updateGeo*Position(..)
so set the new position in the FDM interface. Therefore I had added at the
some code that updates the scenery elevation below the aircraft to *those*
functions.
Ok, not all FDM's do so :/
The attached patch factors out a function computing the scenery altitude at
the current FDM's position. This function is also used in those FDM's which
need to update this value themselves.
Also this patch restores the nearplane setting and uses the current views
altitude instead of the current aircrafts. I think that this should further
be changed to the eypoint's agl in the future.
The agl is again ok in YASim's hud.
Changes
=======
- acmodel.cxx :
we now have an optional new property (/sim/model/texture-path) that is used
as the first path in wich aircraft textures are searched. If textures are not
found there then the usual texture path or model path is used ;
This allows to replace only needed textures for liveries ;
- options.cxx :
added a new --livery=xxx option for the user pleasure ;
this will just set the /sim/model/texture-path property with /livery/xxxx
- od_gauge.cxx, og_gauge.hxx, cockpit.cxx, cockpit.hxx,
generic-instrumentation.xml :
added an helper class that contain a rendering context for glass instrument
or any other opengl drawn instrument ;
- wxradar.cxx, instrument_mgr.cxx, wxradar.hxx :
first experimentation of a weather radar ;
This adds a TACAN instrument to the inventory. Range and bearing are calculated
to the TACAN or VORTAC beacon selected by means of the Channel Selector in the E
quipment/Radio pull-down menu.
A TACAN beacon has also been added to the aircraft carrier Nimitz (channel #029Y
).
Attached is a patch to the airport data storage that I would like committed
after review if acceptable. Currently the storage of airports mapped by ID
is by locally created objects - about 12 Meg or so created on the stack if
I am not mistaken. I've changed this to creating the airports on the heap,
and storing pointers to them - see FGAirportList.add(...) in
src/Airports/simple.cxx. I believe that this is probably better practice,
and it's certainly cured some strange problems I was seeing when accessing
the airport data with some gps unit code. Changes resulting from this have
cascaded through a few files which access the data - 11 files are modified
in all. Melchior and Durk - you might want to test this and shout if there
are problems since the metar and traffic code are probably the biggest
users of the airport data. I've also added a fuzzy search function that
returns the next matching airport code in ASCII sequence in order to
support gps units that have autocompletion of partially entered codes.
More generally, the simple airport class seems to have grown a lot with the
fairly recent addition of the parking, runway preference and schedule time
code. It is no longer just an encapsulation of the global airport data
file, and has grown to 552 bytes in size when unpopulated (about 1/2 a K!).
My personal opinion is that we should look to just store the basic data in
apt.dat for all global airports in a simple airport class, plus globally
needed data (metar available?), and then have the traffic, AI and ATC
subsystems create more advanced airports for themselves as needed in the
area of interest. Once a significant number of airports worldwide have
ground networks and parking defined, it will be impractical and unnecessary
to store them all in memory. That's just a thought for the future though.
There was a patch from Manuel Masing a few months ago which cleaned up
SGLocation's way depending on input values. That means that with that patch
SGLocation does no longer have calls with unneeded input arguments.
I took his patch and integrated that into flightgear and made maximum use of
that changes.
Erik Hofman:
Remove some duplicate code that was moved to simgear/compiler.h
I have prepared a patch that:
- Introduces a FGTileMgr::scenery_available method which asks the tilemanager
if scenery for a given range around a lat/lon pair is already loaded and make
use of that method at some -9999 meter checks.
- Introduces a FGScenery::get_elevation_m method which queries the altitude at
a given position. In constrast to the groundcache functions this is the best
choice if you ask for one *single* altitude value. Make use of that thing in
AI/ATC classes and for the current views ground level. At the current views
part the groundcache is reused if possible.
- The computation of the 'current groundlevel' is no longer done on the
tilemanagers update since the required functions are now better seperated.
Alltogether it eliminates somehow redundant terrain level computations which
are now superseeded by that more finegrained functions and the existence of
the groundcache. Additionally it introduces an api to commonly required
functions which was very complex to do prevously.
I did some profiling of the code and found a few interessant things. Some corrections are obvious like the one in the multiplayer code, the fps is no more divided by 2 or 3 when another plane is on screen.
Other things like collision detection and computation of agl can not really be optimized. I changed a few things in hitlist.cxx but this only give a very low increase of fps. The groundcache eats a lot of cpu but I think that the real way to do it is to use a real collision system like OPCODE or something like that.
And I added an option to disable the recording of replay data. It takes more cpu than we can think.
Changes
=======
- panel.cxx :
moved the computation of the instruments diffuse color outside the texturelayer code
since this is constant during a frame, this is a big speedup for 2D panels ;
- hitlist.cxx :
changed the computation of the intersection between ray and triangle, optimized
the sphere culling by using a normalized direction vector. This can give a
35% speedup on the computation of elevation in some situations ;
- renderer.cxx, acmodel.cxx :
call ssgDrawAndCull with plane scene graph in external or internal view,
calling ssgDrawAndCull with the root scene graph was drawing other players plane
a second time in multiplayer mode ;
- mplayer.cxx :
removed the calls to ssgFlatten and ssgStripify because it was degenerating models,
causing a massive drop in frame rate ;
- replay.cxx :
added an option to disable the recording of the flight
- fgclouds.cxx :
changed the path of cloudlayer properties to match preferences.xml ;
set the altitude of clouds from scenarios to a more correct value if metar is not enabled ;
Changes
=======
- shadowvolume.cxx, renderer.cxx :
- reduced the polygon offset a bit to eliminate some artifact ;
- changed again the cleanup code for objects inside a tile because it could crash on rare occasion ;
- the culling of shadow casters has been rewritten to traverse the scene graph, it should be
a bit faster when there is a lot of objects ;
- the range selector was not correctly handled, sometimes the wrong LOD was casting shadows.
- added the option to display aircraft's transparent objects after the shadows, this will
reduce the problem of shadows being hidden by the transparent object (propeller disk,
rotor, etc). A side effect is that aircraft's transparent objects won't receive shadows
anymore. This is usually a good thing except when the aircraft use a 'transparent'
texture where it should not. A transparent texture in the plib context is a texture
with an alpha channel or a material with alpha <= 0.99.
- model.cxx, animation.cxx, shadowvolume.cxx :
- added an optional <condition> under the <noshadow> animation
- tower.cxx
- correct a rare bug where all occurences of the aircraft are not deleted from the
departure list causing a crash in FGTower::CheckDepartureList function.
I have traced that reset on carrier problem down to several problems. One of
them is the fact that on reset the carrier is updated while the aircraft is
not. That made the aircraft drop down an elevator sometimes. Depending on the
passed realtime while loading some parts of the scenery.
I have introduced the posibility to start directly on the carrier.
With that patch you will have a --carrrier=id argument where id can either be
the pennant number configured in the nimitz scenario or the carriers name
also configured in the carriers scenario.
Additionaly you can use --parkpos=id to select different positions on the
carrier. They are also configured in the scenario file.
That includes the switch of the whole FGInterface class to make use of the
groundcache.
That means that an aircraft no longer uses the current elevation value from
the scenery class. It rather has its own local cache of the aircrafts
environment which is setup in the common_init method of FGInterface and
updated either manually by calling
FGInterface::get_groundlevel_m(lat, lon, alt_m);
or implicitly by calling the above method in the
FGInterface::_updateGeo*Position(lat, lon, alt);
methods.
A call get_groundlevel_m rebuilds the groundcache if the request is outside
the range of the cache.
Note that for the real usage of the groundcache including the correct
information about the movement of objects and the velocity information, you
still need to set up the groundcache in the usual way like YASim and JSBSim
currently does.
If you use the native interface, you will get only static objects correctly.
But for FDM's only using one single ground level for a whole step this is IMO
sufficient.
The AIManager gets a way to return the location of a object which is placed
wrt an AI Object. At the moment it only honours AICarriers for that.
That method is a static one, which loads the scenario file for that reason and
throws it away afterwards. This looked like the aprioriate way, because the
AIManager is initialized much later in flightgears bootstrap, and I did not
find an easy way to reorder that for my needs. Since this additional load is
very small and does only happen if such a relative location is required, I
think that this is ok.
Note that moving on the carrier will only work correctly for JSBSim and YASim,
but you should now be able to start and move on every not itself moving
object with any FDM.
Changes
=======
New volumetric shadows for FlightGear.
There is now two new checkboxes in the rendering dialog to enable/disable shadows
for the user aircraft and for static scenery objects (ie those defined in the .stg files).
AI and random objects are not handled for the moment.
known bugs
==========
- ghost objects
Changes
=======
- correct the transparency probleme when old 3d clouds were enabled
(rendering context with an alpha channel)
- changed rain cone orientation, it can now be viewed from helicopter or chase
view (still not tower view)
- clouds are a bit more yellow/red at dawn/dusk
- weather data is now correctly propagated to the interpolator, this correct
visibility, wind, etc
- the 'metar' weather scenario now immedialty reuse the real metar data
- real metar no more overwrite custom weather scenario
This is another update for the cloud code, a lot of lines but this time I have started to add the doxygen doc.
Misc
====
- corrected a bug when RTT is not available, the current rendering context was
altered
- if RTT is not available then 3d clouds are not drawn at all
- impostors lighting is now recomputed when the sun changes position
- distant objects are no more seen in front of clouds
- blending of distant clouds is a bit better now
- litle optimization of code (uses a less cpu time)
- use layer wind speed and direction (no more hardcoded wind)
- fov is no more hardcoded
Changes
=======
- clouds (cu only) are dissipating/reforming (experimental)
- compute a turbulence factor that depends on surrounding clouds and type of
clouds (experimental)
- clouds shapes are defined in cloudlayers.xml
- type of clouds present in a layer is also defined in cloudlayers.xml
- cloud layers are generated from metar and other misc. data (in progress)
- added a rain effect around the viewer (enabled in the rendering dialog and
when the metar property says so)
- added a lightning effect (enabled in the rendering dialog) : cb clouds spawn
new lightnings
- added a dialog to select from different weather source : metar/property,
a 'fair weather' environment and a 'thunderstorm' environment.
/sim/startup/splash-progress)
- a string in /sim/startup/splash-title is displayed on top of the screen
and by default empty
- the splash image is scaled down if 512x512 is too big
- code cleanup
I have done a patch to eliminate the jitter of 3D-objects near the viewpoint
(for example 3D cockpit objects).
The problem is the roundoff accuracy of the float values used in the
scenegraph together with the transforms of the eyepoint relative to the
scenery center.
The solution will be to move the scenery center near the view point.
This way floats relative accuracy is enough to show a stable picture.
To get that right I have introduced a transform node for the scenegraph which
is responsible for that shift and uses double values as long as possible.
The scenery subsystem now has a list of all those transforms required to place
objects in the world and will tell all those transforms that the scenery
center has changed when the set_scenery_center() of the scenery subsystem is
called.
The problem was not solvable by SGModelPlacement and SGLocation, since not all
objects, especially the scenery, are placed using these classes.
The first approach was to have the scenery center exactly at the eyepoint.
This works well for the cockpit.
But then the ground jitters a bit below the aircraft. With our default views
you can't see that, but that F-18 has a camera view below the left engine
intake with the nose gear and the ground in its field of view, here I could
see that.
Having the scenery center constant will still have this roundoff problems, but
like it is now too, the roundoff error here is exactly the same in each
frame, so you will not notice any jitter.
The real solution is now to keep the scenery center constant as long as it is
in a ball of 30m radius around the view point. If the scenery center is
outside this ball, just put it at the view point.
As a sideeffect of now beeing able to switch the scenery center in the whole
scenegraph with one function call, I was able to remove a one half of a
problem when switching views, where the scenery center was far off for one or
two frames past switching from one view to the next. Also included is a fix
to the other half of this problem, where the view position was not yet copied
into a view when it is switched (at least under glut). This was responsible
for the 'Error: ...' messages of the cloud subsystem when views were
switched.
have a "property" mode as well as the original "binary" mode. The property mode
will allow the remote module to request any set of properties, and it will send
those properties each frame. The remote module can reply with a list of arbitrary
property name/value pairs to update on the FlightGear side.
This is a first stab, so it's not the cleanest, most well concieved code, but it
allows an external module (communicating via a pipe) to have a huge amount of
flexibility in the data in can access and update.
Make SDL window resizable; This exposes the same problem that many
GLUT users have: resizing up may cause a temporary switch to software
rendering if the card is low on memory. Resizing down again switches
back to HW rendering. (KSFO is texture intensive, but there are no
problems in LOWL, and elsewhere.) Less and less users will have the
problem as cards become better, and it's no reason not to allow
resizing altogether.
a safe undersleep() to conserve cpu. Essentially we undersleep our target by
just a bit (to avoid the chance of oversleeping.) Then we finish off the
remaining time slice with a busy-wait loop.
Norman Vine wrote :
> Frederic Bouvier writes:
>
>> Quoting Andy Ross:
>>> * Hopefully in a CPU-friendly way. I know that older versions of
>>> the NVidia drivers did this by spinning in a polling loop
>>> inside the driver. I'm not sure if this has been fixed or not.
>>>
>>> From my experience, the latest non-beta Windows NVidia driver seems to eat CPU
>>
>> even with sync to vblank enabled. The CPU usage is always 100%.
>
> Buried in the PPE sources is a 'hackish' but portable way to limit CPU usage if the desired framerate is met
>
> /*
> Frame Rate Limiter.
>
> This prevents any one 3D window from updating faster than
> about 60Hz. This saves a ton of CPU time on fast machines.
>
> ! I THINK I MUNGED THE VALUE FOR ulMilliSecondSleep() NHV !
> */
>
> static ulClock *ck = NULL ;
>
> if ( frame_rate_limiter )
> {
> if ( ck == NULL )
> {
> ck = new ulClock ;
> ck -> update () ;
> }
>
> int t_ms = (int) ( ck->getDeltaTime() * 1000.0 ) ; /* Convert to ms */
>
> if ( t_ms < 16 )
> ulMilliSecondSleep ( 16 - t_ms ) ;
> }
>
>
I implemented the method pointed out by Norman. It works great on windows and saves me a lot of CPU cycles. This way, I can get the same framerate in moderately populated areas and have CPU idle 50% of the time instead of wildly looping in the NVidia driver while waiting to sync on vblank.
It has been tested on Linux by Melchior. He saw the same gain in CPU cycles.
I have added a --aspect-ratio-multiplier=x.xx option to give some end user
control over the aspect ratio. (This may seem a little strange, but it's a
building block towards the capability of doing asymmetric view frustums in
FlightGear.)
ssgSetNearFar(). This by default creates a symmetric view frustum which is
typically what an application wants.
However, to get control of the view frustum in order to build support for
asymmetric view frustums, we need to wrap these calls with a bit of our own
logic.
This set of changes wraps all calls to ssgSetFOV() and ssgSetNearFar() with
FGRenderer methods.
I also standardized how the FGRenderer class is handled in globals.[ch]xx.
This led to some cascading changes in a variety of source files.
As I was working my way through the changes, I fixed a few warnings along
the way.
I just heard from John Wojnaroski that you and he are going to work on getting
a flightgear demo machine up for the linux expo thursday and Friday. John
indicated that he would very much like to get a CVS version with the new
traffic code up and running before the expo.
RE: --aircraft=ufo in system.fgfsrc is ignored
To change a 'feature', one that has been mentioned here many
times, and again recently, place the following code block
into fgInitFGAircraft.
In its favour, I would argue this means FG can be run without
a command line, provided FG_ROOT has been set in the
environment, and that seems to me, as it should be ... ;=))
Perhaps the only counter, is that system.fgfsrc is read twice,
but so are others, like .fgfsrc, for other (local) options ...
or system.fgfsrc should .nt. be used for 'aircraft' ?
The following patches to SimGear & FlightGear ...
- create an FGMetar abstraction layer, whose purpose is:
* provide defaults for unset values
* interpolate/randomize data (GREATER_THAN)
* derive additional values (time, age, snow cover)
* consider minimum identifier (CAVOK, mil. color codes)
- add rain/hail/snow/snowcover support on the METAR side
- add max age of METAR data handling (currently set to
- add support for an external METAR cache proxy server
- add CAVOK handling
- set missing year/month in regular METAR messages
- fix a small bug in metar.cxx (wrong return value)
explicit calls to shutdown_all() which was causing this to be called twice.
This could cause problems with some IO modules (such as attempting to close
an invalid file descriptor the second time.)
a single apt.dat.gz file which is in the native X-Plane format.
To do this I wrote a front end loader than builds the airport and runway
list. Some of the changes I needed to make had a cascading effect, so there
are minor naming changes scattered throughout the code.
I've finished the emigration of the radiostack, and I've also removed it
completely. It turned out that the comm radio is completely implemented in
the ATC subsystem. I've changed the affected ATC files to point
to /instrumentation/com, but I guess that the maintainer of the ATC code
should decide wether to make it configureable, and how.
I also had to change some files in Network and Main. The changes in network
should be obvious, but the changes in Main were a bit suspect. The files
included radiostack.hxx, but they weren't directly depending on
radiostack-hxx. They were depending on other files that were included by
radiostack.hxx. I got it to compile, but I'm not sure if I included the
correct directly depending file.
For the data directory I changed every occurrence of /radios/
with /instrumentation/ with this simple one-liner that I found on the net:
find -name '*.xml' -type f | xargs perl -pi -e
's/\/radios\//\/instrumentation\//g'
Instead of me sending all the files that got changed by this I suggest that
you execute the one-liner yourself. Of course I can not guarantee that this
will work perfectly, but I considered hand editing to be not an option (I'm
lazy). I don't want to test every aircraft to see if everything still works,
I think it's better to wait and see if anyone complaints about broken nav
radios/instruments.
Use a suggested exit method as described in the SDL_Quit man page. (fgOSExit() is still uncalled in both fg_os.cxx (glut) and fg_os_sdl.cxx, which makes these functions kind-of useless.) The other changes are fixes for gcc 3.3.4 warnings.
The caption should already be set when the window is opened. This is
important for some window managers. (KDE's kwin, for example, can store
special settings for certain windows, such as "no border" and "always
on top". KDE uses the window title to determine if a special rule is
to be applied. KDE will be made more tolerant, too.)
After applying the attached patches (based on latest CVS) you should
have a new option available within your version that should also
show up using fgfs --help, the syntax is:
fgfs --min-status={level} --show-aircraft
whereas "level" can be anything between
"alpha","beta","early-production" and "production"
Of course running something like
fgfs --min-status=alpha --show-aircraft
should not return any aircraft right now, as none of the
current aircraft definition files in your base-package is using the
required
<status></status>
tag - but you can easily give it a try by adding something like
<status>alpha</status>
The tag should be placed as a sub-tag within <sim> - so directly behind
the <description> tag would be just fine and straight-forward.
I've added two new debug log types for the instrumentation and systems. They
used to use the autopilot debug log, because I couldn't figure out how to
make new log types. Well, now I have figured it out. ;-)
Don't overwrite user settings from config files.
fgfs had in any case set bump-mapping to false, no matter if this
node did already exist (because it was defined in a config file).
This is a patch to make display list usage optional. They are on by default.
Use --prop:/sim/rendering/use-display-list=false to use immediate mode.
There is also a change in exception handling in main.cxx and bootstrap.cxx
erly known as trRenderFrame) is now declared as a NULL function pointer and ass
ignment of the proper function is now done in FlightGear (jpgRenderFrame=FGRend
erer::update).
a working state. I still see an anomoly when taking a screen shot from inside
a 3d cockpit, but external (chase/tower) views seem to work well. I also
added a property to control how many screen-res tiles are generated in the
output. Theoretically, you can now generate unlimited resolution screen shots,
or limited only by your disk space and patience.
Today I successfully generated a 20*1024 x 20*768 (20480x15360) resolution
screen shot. If you rendered that at 100 dpi it would cover a poster of
about 17 feet by 12.8 feet.
Good luck trying to display something that big or convert it to anything
useful on a typical PC. :-)
split). If SimGear is configured --with-jpeg-factory, then FlightGear
will fail to build unless this function is present.
FIXME: this is very messy architecturally -- find a better solution,
like passing this explicitly as a callback to the libJPEG class
(SimGear should not have a dependency on FlightGear).
Split up main.cxx into a program manegement part (which remains in
main.cxx) and a render part (the new renderer.?xx files). Also turn
the renderer into a small class of it's own. At this time not really
exctining because most of the stuff is still global, but it allows us
to slowly migrate some of the global definitions into the new class.
The FGRenderer class is now managed by globals, so to get the renderer
just call gloabals->get_renderer()
At some pijt it might be a good idea to also turn the remaining code in
main into a class of it's own. With a bit of luck we end up with a more
robust, and better maintainable code.
this was always only meant to be a test program for the metar lib, but now
that people are referring to it as a means to get metar reports, I think a
usage info is desirable. The list of test ids, on the other hand, isn't
necessary any more. This can still be handled by a Makefile or the commandline.
I'm all for keeping this tool in cvs, however. And also the not-used stuff
therein is a welcome source for how to use the SGMetar class.
A good elevation is critical for proper glide slope modeling. This patch
assigns the average field elevation to any ILS component that doesn't have
a valid elevation.
Also, for an ILS approach, use the GS transmitter elevation for glide slope
calculations rather than the localizer elevation, in some cases this can
make a big difference.
