Different Formulas to find targets' coordinates?

[DarkCrow]

In another thread Ramsay provided us with a formula to accurately calculate the coordinates of a target using the Viviane and NADIR:

 

UTM N

Cos (bearing + declination + map correction) * (range/10) + CurrentUTMNorth

 

UTM E

Sin (bearing + declination + map correction) * (range/10) + CurrentUTMEast

 

I have some ideas for some missions and want to do something a little different but don't have the math skills and understanding to figure out how to do it even with the power of google. So I figured this would be a good thread for those of you that know the formulas could share with us here. (Also I want a formula that can be done on a scientific calculator and not an App or program that does it for you. It's more fun!)

 

Here's a scenario: Target is a small shed, in a heavily defended city, that has a omnidirectional antenna broadcasting data in the Low Frequency range. You are able to pick this up and use your ADF to find the bearing to it but can not overfly the city to pinpoint it. (Basically a NDB.) You can mark your current coordinates using the NADIR. Use your Viviane and the formula above to calculate another point's coordinates a set distance perpendicular to your target. Fly to that location and find the heading to the antenna using your ADF. So what formula would I use with UTM coordinates to find the targets coordinates?

 

I have 2 sets of coordinates, the distance between those coordinates and the bearing to target from both sets of coordinates.

 

This could also be useful for calculating a targets coordinates outside of the laser ranger finder's 15000m range. If you can see the target you would still be able to use the Viviane's bearing.

 

 

 

 

 

 

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[DarkCrow]

I forgot the mission editor only allows you to transmit as low as 300 Khz, so Medium Frequency Range :)

 

 

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[Ramsay]

I have 2 sets of coordinates, the distance between those coordinates and the bearing to target from both sets of coordinates.

If you google "triangulation" you will find lots of stuff.

 

 

Note: the angles are exaggerated for clarity.

 

If the distance between the measuring points is small compared to the distance to the NDB/transmister, the distance to the transmitter can be approximated by the distance to the base line.

 

You now have the bearing and approximate distance to the radio transmiter to plug into your fomula

 

UTM N

Cos (bearing + declination + map correction) * (range/10) + CurrentUTMNorth

 

UTM E

Sin (bearing + declination + map correction) * (range/10) + CurrentUTMEast

[DarkCrow]

Thanks a bunch Ramsay. Going to play with this now. I think the may be a reason to use the Polar Coordinate Function of the NADIR. I can start at position "A" get the coordinates, use the viviane to get coordinates a set distance away ( This would be the center of my "Baseline". The point which I would find the distance to.) Then use the polar function to create the 3rd waypoint an equal distance away on the same heading. This would be point "B" where I get my other angle measurement. Time to test it out. Thanx again.

 

 

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[Ramsay]

I've been playing around with this but not really got consistent results (lots of error/variation).

 

I think, I like this formula best

 

distance to transmitter = base x tan (base angle to transmitter)

 

 

tan 84° = ~ 10

 

To estimate the distance to a ADF transmitter

• turn to put the transmitter at your 3 or 9 o'clock
  
• create a way point by copying present position
  
• note the bearing to the transmitter
  
• continue on the same 90° heading until the transmitter bearing changes 6°
  
• the distance to the transmitter = 10x the way point distance (+/- 15%)
  

[DarkCrow]

Took me a really long time to attempt the way I just did it because I was trying to learn it so I have only done it once. I was within 3 seconds North and 4 seconds west.

 

I created a waypoint then created another waypoint 5000m away. I then used the polar coordinate function to create a waypoint 10000m away on the same heading. I used the NADIR to show my precise heading. I tuned to the NDB so the ADF needle would point to it. I then used the Viviane in slaved mode to aim at the needle and give me precise heading. Subtracted the 2 headings to get my angle for that formula. I then flew to waypoint 3 and did the same. I now had my distance to waypoint 2. I flew to waypoint 2 and got my heading there for the original formula. I was looking for an invisible target because I just set the radio trigger on the bulls eye so I wasn't sure how close I was but my range to the target from waypoint 2 or "d" in the formula was only 2337 meters.

 

 

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[DarkCrow]

I'll give it a go the other way when I get some time again. Sure was fun and thanx fir the help.

 

 

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[DarkCrow]

I also should note that I did my test in Nevada. At the location I was at I had a 12.19 declination and the MGRS were aligned to true north so I didn't need map correction.

 

 

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[DarkCrow]

 

I made up this form to make it easier to plug in all the info I need. I don't have internet at my house right now but when I get to a location that has it I'll upload it just incase anybody would like it.

 

 

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[DarkCrow]

I've been having a lot of trouble getting the d = l sin a sin b / sin ( a + b ) to work since the first time I did it. I tried that other formula d = l * tan A and boy was that a lot easier. I did it within a range I could verify with the laser (roughly 13500m) and I was within 500 meters. I think it's really hard to get accurate enough angles without actually seeing the target though. Basically it can give you a general idea of the area to search but not to call in an artillery strike.

 

 

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[Ramsay]

Yeah, I've been using it as ADF recon tool, rather than any type of precision targeting.

 

I tested a couple of scenarios

• estimating NDB Ali from Batumui (180km @ 60° Magnetic) and after flying 330° M for 19 km (for a 6° deflection) was happy with a 190 km +/- 19 km estimate.
  
• estimating the distance to random downed pilot for CSAR, flying for 2 km the adf needle quickly deflected past 6°, so I knew the pilot was no further than 20 km max. (he was at 12 km).
  

I imagine ADF can be used to track enemy transmissions and ADF ranging is a means of estimating when to start using stealth and caution for target acquisition/recon or terrain masking to avoid SAM's.

 

I was thinking of the prominent aerials on the front of UK Gazelles when testing but I'm not 100% sure they're used for ADF.

[wolf5]

These antennas are used for homing