View Full Version : Aircraft position calculation

9th Mar 2004, 09:23
Hi all,

I have a question here:

How do you calculate an aircraft current position (latitude, longitude, and altitude) based on:
- the aircraft last position (latitude, longitude, and altitude),
- the elapsed time (now - last position time),
- the aircraft speed (knot), and
- the aircraft direction (stated using angle from north)?

Thanks a lot.

10th Mar 2004, 16:25
It's easy! Just use an IRS :)

It's impossile to calculate altitude using that information unless it remains the same...

Calculating distance from a point is easy (distance = speed x time), but things get tricky very quickly when you want the answer as a Lat/Long. Actual distance (what you can actually work out) between degrees of longitude will vary with latitude... It's not impossible though!

11th Mar 2004, 02:24
1. Lay chart on knee

2. Find last two or 3 marked fixes.

3. Extrapolate OR use last known track made good OR use heading + reasonable drift allowance to give line of position

3. Note time.

4. Note last calculated groundspeed OR TAS + reasonable +/- wind adjustment.

5. Use 3. & 4. to calculated distance run.

6. Mark this DR distance along LoP.

7. Read lat. & long. from map.

8. Look at altimeter.


1. Press button on GPS to read current lat. & long.

2. Go "Huh????" :confused:

3. Press other buttons to change display to Bearing/Distance from waypoint.

4. Look at altimeter.

:} :} :}