Calculating Glideslope

[COBS]

I am trying to calculate the current glideslope angle in degrees to a
known ground position .

Horizontal distance is.

(L:DistanceMarkPos,nmiles) 6076 *

Vertical distance is,

(A:Indicated Altitude, feet) (L:MarkGROUND ALTITUDE, feet) -

I tried the following without success ,

%((A:Indicated Altitude, feet) (L:MarkGROUND ALTITUDE, feet) - (L:DistanceMarkPos,nmiles) 6076 * / tg  * pi 180 /) %!03d!%

Any assistance would be appreciated .

Cheers
Karol

 

[rcbarend]

Hi Karol,

At the end of the formula, both the function (tg) and calculation order is wrong ..

Should read : ..... atg 180 pi / *)

Or even simpler .... atg rddg)

( so use arc tangens function to calculate the angle; rddg converts an angle in radians into degrees )

Cheers, Rob

 

[COBS]

Hi Rob

Thank you.
It now works beautifully , I used the following ,

%GS %((A:Indicated Altitude, feet) (L:MarkGROUND ALTITUDE, feet) - (L:DistanceMarkPos,nmiles) 6076 * / atg rddg ) %!5.2f!%

I created an instrument for my panel , then realised that it had other potent capabilities.

So I just had a little fun with it ,
with the above line of code I can now conduct precision approach
and landings anywhere even in zero visability conditions .
That includes isolated paddocks , lakes , rivers , roads , and the fun one is on hardened rooftops
on top of 500' office blocks.
I have precision , bearing to heading , bearing to touchdown spot . distance to go in feet , height above applicable surface in feet ,
and now the current approach glideslope angle .

Cheers
Karol

 

[COBS]

An interesting aspect that results from the above glideslope readout is that I can be
at say 35,000' and 90nm from my defined spot.
I then turn till the heading = bearing , then push the nose down till the
glideslope value remains constant , then maintain that value I will descend
to the target spot , rather neat !

Cheers
Karol

 

[rpmc]

An interesting aspect that results from the above glideslope readout is that I can be
at say 35,000' and 90nm from my defined spot.
I then turn till the heading = bearing , then push the nose down till the
glideslope value remains constant , then maintain that value I will descend
to the target spot , rather neat !

Yep, very neat. Except for that hill before the airport . Presumably, your target spot is some sort of enroute or approach fix. CFIT.

Your stuff is always very cool to follow.

Bob

 

[COBS]

Hi Bob ,

Thank you .
Hills .. what hills ? , in a cloud you see no hills , therefore no angst ; .

I created a simple instrument to emulate a real world military feature , and that works nicely.

But .... I have to admit the above is much more fun .
I'll be putting it in my Choppers , seaplanes , and cropduster/firefighter aircraft.

I will in a new thread post the code for this function , it's only a Demo unit ,
it's display format could be bettered to make it more pilot friendly.
Others might find it useful .

Cheers
Karol

 

[rpmc]

Hills .. what hills ? , in a cloud you see no hills , therefore no angst ; .

hahaha. CFIT. R.I.P.

 

[COBS]

Presumably, your target spot is some sort of enroute or approach fix.

No , I create my own spots on the fly anywhere that I desire , while it has it's limits ,
it's much more flexible .
The same applies to any specific hardened rooftop that you might choose .

It kind of has a tape measure , so you can determine the length of a paddock or stretch of a river
to establish if it long enough to land/take off from , and additionally you can go off any distance
then come back later and find your obscure spot and align with your saved landing heading and land
at the exact spot.

Cheers
Karol