Mark Position - GEOCALC reciprocal runway ?

[COBS]

I made a "MARK POSITION" instrument that can be used to conduct ILS like
precision approach and landings at any location such as :-
roads , paddocks , ordinary small airfields , rivers , lakes and on oceans.

It saves ,
1. a precise Lat/Long spot (used as touchdown point of runway)
2. a heading value , 'mark heading' (used as runway centerline heading)
3. the ground elevation at that location

It calculates ,
1. bearing to mark position
2. distance to mark position
3. height above that surface
4. glideslope angle , from aircraft to mark position

The above provides ILS approach precision accuracy , but only in the
'mark heading' direction .
ie; only for one end of the runway .

What I now want to do is ,
1. provide a runway length setting arrangement , whereby the pilot enters a
number ( eg; 7,525' ) , pilot determines length required .
That's easy to do and set .
2. calculate other end runway heading , that's easy , its
'mark heading' plus or minus 180 degrees .

3. " generate a Lat/Long position for other end of runway "

4. create a Flip Flop switch to toggle the "MARK POSITION" to either end of the runway
at pilots discretion , thus enabling ILS precision approach at either end .
This switching is easy.

My problem is this one ,
3. " generate a Lat/Long position for other end of runway "

What I need is a GEOCALC format based on the following ,

Known elements are ,
1. MARK POSITION Lat/Long
2. Distance , it's the runway length ( eg; 7,525' )
3. Bearing , it's 'mark heading' plus or minus 180 degrees

Unknown element ,
1. Find/ calculate Lat/Long position for other end of runway

How do I do that GEOCALC ?

I would appreciate a GEOCALC example if possible .

Cheers
Karol

PS; following are links to previous threads on this instrument.
http://www.fsdeveloper.com/forum/threads/calculating-glideslope.430164/
and,
http://www.fsdeveloper.com/forum/threads/mark-position.430178/

 

[Roy Holmes]

http://www.movable-type.co.uk/scripts/latlong.html
This site has all the math you need to establish the position of the other end of the runway
Roy

 

[COBS]

Roy,

Thank you , I had a very brief quick look at it , will need to look more carefully.
It looks as if that will help with another project that I'm doing where the large distances involved need to
take in the shape of the Earth , in that project my projections over 700-800nm have been close but
not accurate , out by several nm and a couple of degrees , so thank you again.

Looking at the SDK for GEOCALCs , I came up with the following format.
I have yet to test it to see if it works .

           (L:Known Runway End Latitude, degrees) (>@c:GeoCalcLatitude1,degrees)
           (L:Known Runway End Longitude, degrees) (>@c:GeoCalcLongitude1,degrees)
             (L:BearingMarkPos,degrees) (>@c:GeoCalcBearing,degrees) 
             (L:Runway Length,nmiles)(>@c:GeoCalcDistance,nmiles)       
           (@c:GeoCalcExtrapolationLatitude,degrees) (>L:Un Known Runway End LATITUDE,degrees) 
           (@c:GeoCalcExtrapolationLongitude,degrees) (>L:Un Known Runway End LONGITUDE,degrees)

Note: the runway reciprocal +/- 180 degrees has to be applied separately and after the GEOCALC is done.

Cheers
Karol

 

[rpmc]

Hello Karol,

Why don't you take a look at this Guidebook, page 183

The GeoCalc variables that should be used are:

GeoCalcLatitude1
GeoCalcLongitude1
GeoCalcLength
GeoCalcAzimuth1
GeoCalcExtrapolationLatitude
GeoCalcExtrapolationLongitude

Your script will work if you use GeoCalcLength and GeoCalcAzimuth1 instead of GeoCalcDistance and GeoCalcBearing. Note that GeoCalcAzimuth1 must be in degrees TRUE.

Additionally, I imagine that most everyone has found this excellent reference, Ed Williams Aviation Formulary v1.46.

Bob

 

[COBS]

Hi Bob,

Thanks for the reminder , I had read the Geocalc Group section after I printed out the Guidebook ,
but had forgotten about it.
I'll need to re read and understand it better , that and the references provided by both Roy and yourself ,
I need that sort of info for a few things that I'm tackling .

Still trying render this instrument into a more pilot friendly affair , generally what I'm after is a
ILS style display with dynamic lateral and vertical bars with funtionality for any GS , it looks
as if it might need at least two displays , ILS and ADI , it's not for any particular purpose at the
moment ; exploring it's possibilities just appeals to me .

Cheers
Karol

 

[rpmc]

generally what I'm after is a
ILS style display with dynamic lateral and vertical bars with funtionality for any GS , it looks
as if it might need at least two displays , ILS and ADI , it's not for any particular purpose at the
moment ; exploring it's possibilities just appeals to me .

From my understanding of your Mark Position, it seems you're thinking of a sort of GPS LPV approach. Those are flown using standard HSI, CDI or equivalent glass cockpit displays for horizontal and vertical position information, so I'm wondering the need for an ADI? It's radio beacon-based. Actually, I suppose that's not what you were getting at.

Anyway, I'm sure you'll enjoy putting this together. Your concept gauges are imaginative and you're showing many things that can be done with an understanding of the gps module.

Regards,

Bob