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Thread: Terrain Following Radar

  1. Default Terrain Following Radar

    Guys & Gals (maybe),

    Does anybody know of a Terrain Following Radar that can be run by an autopilot for use in low level military flying ?

    I have searched and searched but not found anything that works, but sometimes a quick question can bring new options to light.

  2. Default

    IIRC, there is an heavily modified Alphasim F-111 which should offer a TFR. Look for F-111, HUD, TFR in the library.

    Paolo

  3. #3

    Default

    i don't know if that'll do what you're after, but here goes.


    Code:
    <Gauge Name="TFR" Version="1.0">
    
    	<Image Name="TFR_Background.bmp" Bright="Yes"/>
    
    	<Update>
    		(L:TFR, bool)
    		if{
    			(L:TFR Altitude Hold Var,feet) (A:GROUND ALTITUDE,feet) + (&gt;K:AP_ALT_VAR_SET_ENGLISH)
    			(A:AUTOPILOT ALTITUDE LOCK VAR,feet) (A:Plane Altitude,feet) - abs 50 &gt;
    			if{
    				(A:AUTOPILOT ALTITUDE LOCK VAR,feet) (A:Plane Altitude,feet) - 0 &gt;
    					if{ (L:TFR VERTICAL HOLD VAR,feet per minute) (&gt;K:AP_VS_VAR_SET_ENGLISH) }
    					els{ (L:TFR VERTICAL HOLD VAR,feet per minute) /-/ (&gt;K:AP_VS_VAR_SET_ENGLISH) }
    			}
    			(A:YOKE Y INDICATOR,percent) 5 &gt;
    			if{ (&gt;K:AP_ALT_HOLD_OFF) }
    			els{ (A:Autopilot altitude lock, bool) ! if{ (&gt;K:AP_ALT_HOLD_ON) } }
    		}
    	</Update>
    
    	<Element>
    	
    		<Element>
    			<Position X="16" Y="26"/>
    			<Text X="33" Y="16" Bright="Yes" Length="3" Font="Glass Gauge" Color="%((L:TFR, bool) if{ 'White' } els{ 'Orange' } )" Adjust="Center" VerticalAdjust="Bottom" Fixed="Yes" Multiline="No">
    				<String>TFR</String>
    			</Text>
    		</Element>
    
    		<Element>
    			<Position X="115" Y="14"/>
    			<Text X="44" Y="16" Bright="Yes" Length="4" Font="Glass Gauge" Color="Orange" Adjust="Center" VerticalAdjust="Bottom" Fixed="Yes" Multiline="No">
    				<String>%( (L:TFR Altitude Hold Var,feet) abs )%!04d!</String>
    			</Text>
    		</Element>
    
    
    		<Element>
    			<Position X="115" Y="38"/>
    			<Text X="44" Y="16" Bright="Yes" Length="4" Font="Glass Gauge" Color="Orange"  Adjust="Center" VerticalAdjust="Bottom" Fixed="Yes" Multiline="No">
    				<String>%( (L:TFR VERTICAL HOLD VAR,feet per minute) abs )%!04d!</String>
    			</Text>
    		</Element> 
    
    	</Element>
    
    
    	<Mouse>
    		<Area>
    			<Click/>
    
    			<Area Left="8" Top="12" Width="48" Height="42">
    				<Cursor Type="Hand"/>
    				<Click>(L:TFR, bool) ! (&gt;L:TFR, bool) </Click>
    			</Area>
    
    
    			<Area Left="173" Top="9" Width="48" Height="24">
    				<Area Width="24">
    					<Cursor Type="DownArrow"/>
    					<Click Repeat="Yes">
    						(L:TFR Altitude Hold Var,feet) d 0 &gt;
    						if{ 10 - (&gt;L:TFR Altitude Hold Var,feet) } 
    					</Click>
    				</Area>
    				<Area Left="24">
    					<Cursor Type="UpArrow"/>
    					<Click Repeat="Yes">
    						(L:TFR Altitude Hold Var,feet) d 9990 &lt;
    						if{ 10 + (&gt;L:TFR Altitude Hold Var,feet) } 
    					</Click>
    				</Area>
    			</Area>
    
    			<Area Left="173" Top="33" Width="48" Height="24">
    				<Area Width="24">
    					<Cursor Type="DownArrow"/>
    					<Click Repeat="Yes">
    						(L:TFR VERTICAL HOLD VAR,feet per minute) d 0 &gt;
    						if{ 100 - (&gt;L:TFR VERTICAL HOLD VAR,feet per minute) } 
    					</Click>
    				</Area>
    				<Area Left="24">
    					<Cursor Type="UpArrow"/>
    					<Click Repeat="Yes">
    						(L:TFR VERTICAL HOLD VAR,feet per minute) d 9990 &lt;
    						if{ 100 + (&gt;L:TFR VERTICAL HOLD VAR,feet per minute) } 
    					</Click>
    				</Area>
    			</Area>
    
    
    		</Area>
    	</Mouse>
    
    </Gauge>

    i would have attached the .cab, but the board software keeps telling me "invalid file", despite announcing "zip" being a valid file extention.

  4. Default

    Paolo, thanks for this, I'll install it and see if it works.

    Wyvern, is this the .cab from the F111 or something totally different ?

  5. #5

    Default

    it's a modification of a "terrain avoidance radar" gauge i wrote myself.

    originally, it only set the autopilot reference altitude higher when the terrain came up to the plane altitude.
    now it also sets it lower when the terrain falls away.
    there's two parameters, altitude offset and vertical speed to be applied when the difference gets too high.
    it doesn't look ahead though, it works with the terrain elevation under the aircraft.
    when activated, it also temporarily disables the AP when the yoke is pulled more than 5% to enable control should there be an obstacle that the gizmo can't handle.

  6. Default

    I have looked at the code of the TFR gauge (coming from the F-111): the idea is similar. The weak point is that a true TFR would scan the terrain elevation ahead of the aircraft to react accordingly, whereas this gauge looks at the elevation below the aircraft and does something.

    In the F-111 documentation, it is clearly stated that the TFR can't avoid to slam the aircraft into an hill or negotiate a valley in and out, unless the speed is low enough.

    I wonder whether it could help to introduce an "height history" into the gauge to predict better what to do (e.g. if the height is constantly reducing, pull up further and if the height is constantly increasing, pull down further), this should a concept similar to a basic PID controller system.

    Paolo

  7. #7

    Default

    that would only give you less altitude once the ridge comes up.

    the only way for this i do see is a C-gauge that can check the elevation grids of the actuall scenery and acts accordingly.

  8. Default

    Guys, you are starting to talk my language now. The idea is obviously to look at the terrain ahead to give the aircraft time to adjust for ground changes. I'm no programmer so have not a clue how this would be achieved. Ideally, the distance ahead of the aircraft to be looked at would be dependant on ground speed.

    Now, FS obviously knows where you are in the world as it is compiling relative things in the background. Is there a way to tap into this ? Or, is there a way to give FS a set route, so that FS knows the elevation for the whole flight and use this ?

    Clyde

  9. #9

    Default

    well, technicall you can program a GPS route with waypoint altitudes. the default GPS doesn't show that altitude, but it does show the required vertical speed in feet/second (don't ask me who came up with -that-).
    it shouldn't take much to actually program a gauge that reads the GPS altitude data and sets the autopilot. programming the route into the autopilot is another matter, as all the info you normally get is the elevation of facilities.
    on the other hand, that could be done with an offline-tool.

  10. #10

    Default

    Generally speaking, the easiest way would be to use SimConnect (FSX only unfortunately!) to create "probe objects" ahead of the a/c's position, read the terrain elevation directly under each "probe object", then destroy the "probe objects." This is of course a continuous loop...

    Taking the received data, one could then construct a fairly accurate "terrain map" ahead of the a/c, and use that to drive the terrain following algorithim.

    This is of course a very simplified explanation of the "bare bones" of such a system.
    Bill Leaming
    Gauge Programming - 3d Modeling Military Visualizations
    Flightsim.com Panels & Gauges Forum Moderator
    Flightsim Rig: Intel Core i7-2600K - 8GB DDR3 1333 - EVGA GTX770 4GB - Win7 64bit Home Premium
    Development Rig1: Intel Core i7-3770k - 16GB DDR3 - Dual Radeon HD7770 SLI 1GB - Win7 64bit Professional
    Development Rig2: Intel Core i7-860 - 8GB DDR3 Corsair - GeForce GTS240 1GB - Win7 64bit Home Premium
    NOTE: Unless explicitly stated in the post, everything written by my hand is MY opinion. I do NOT speak for any company, real or imagined...

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