Waypoint is off by 2 miles?

[truebrit]

I made a quick mission to practice dumb bombs starting in the air about 30 miles out, but the target waypoint I set in the mission editor is about 2 miles south of what the HSI tells me in mission. I've never noticed this before(been a few months since I played).

What am I doing wrong?

I'll attach the .miz file.

 

F-4E Dumb Bomb Practice Argentina.miz

[Raven (Elysian Angel)]

INS drift? Isn't there an options somewhere that lets you simulate how long you've been in the air already when you spawn in, and thus the accumulated INS drift up until that point?
I don't usually air spawn so I don't know for sure  

[QuiGon]

6 hours ago, truebrit said:

I made a quick mission to practice dumb bombs starting in the air about 30 miles out, but the target waypoint I set in the mission editor is about 2 miles south of what the HSI tells me in mission. I've never noticed this before(been a few months since I played).

What am I doing wrong?

I'll attach the .miz file.

 

F-4E Dumb Bomb Practice Argentina.miz 14.73 kB · 1 download

Depending on how long you've been airborne when seeing this difference, it might just be the usual INS drift of the Phantom's nav system as it is not equipped with GPS to correct the drift.

Unfortunately I can't check your mission as it requires user mods that I don't have (P8, TU214).

[Zabuzard]

Yeah. Also cant view it unfortunately.

The Phantom, if aligned fully, has a general drift characteristic of 3nm CEP/h. Not sure how long you have been flying already when you reached that point or if you perhaps pulled some hard turns and Gs which would increase the drift etc, but its very possible that this is just within limits and normal behavior.

Also sth you might want to check are your sliders for Aircraft Condition and Wear/Tear in the Mission Editor.

Make sure that every flight plan includes NAV FIX points.

[Pillowcat]

Isn't it just coordinates discretization error, as minimal operated by phantoms INS value is 1 arcminute, which is up to ~2nm?

[QuiGon]

Just now, Pillowcat said:

Isn't it just coordinates discretization error, as minimal operated by phantoms INS value is 1 arcminute, which is up to ~2nm?

Maybe. Hard to tell without being able to watch the track file.

[Pillowcat]

1 hour ago, Pillowcat said:

up to ~2nm

OMG. up to ~2km of course, or exactly 1nm by definition, my bad lul

from .miz file:
start point
["y"] = -593983.73314055, ["x"] = 48946.089089157
target
["y"] = -703031.43400357, ["x"] = 25813.042834565
["ETA"] = 212.63347472276,
so ~60nm, ~4min, and "["Quality"] = 100" seems to mean good aircraft condition

[Zabuzard]

OMG. up to ~2km of course, or exactly 1nm by definition, my bad lul
from .miz file:
start point
["y"] = -593983.73314055, ["x"] = 48946.089089157
target
["y"] = -703031.43400357, ["x"] = 25813.042834565
["ETA"] = 212.63347472276,
so ~60nm, ~4min, and "["Quality"] = 100" seems to mean good aircraft condition

A 1nm deviation after 4min of flight, potentially with some maneuvring, seems generally uncommon but still within limits.

Is it sth that happens again if you retry the mission?

[Sickdog]

I've become interested in this thread because I'm trying to employ a level bombing technique from altitude (10,000 feet) (and maybe a subject for another thread entirely), and I'm testing out my method by flying over a NAV computer waypoint as precisely as possible to drop my bombs a pre-calculated distance from target (using the bombing table). The trouble I'm having is my NAV computer is not flying me directly over my waypoint. I understand INS drift is most likely the cause, but surprised to see with my technique how inaccurate it is. 

My technique:

-Caucasus Map, flown out of Anapa airbase.
-ME: 100% Aircraft condition
-ME: 0% Wear and Tear
-ME: Reference Aircraft box Check Marked (should be a perfect airplane)
-Hot Start on the ramp
-Fine INS alignment before making waypoints with F-10 Map Markers
-Use a NAV Fix prior to overflying my waypoints for bombing
-No major maneuvering (G's) to cause excess drift on the INS
-Overflying my waypoints within 4-5 minutes of my NAV Fix. 

The results have shown me consistently to the right of my Waypoint by less than a mile, but enough to make me miss my target by 2000-3000' feet laterally. And when repeating this procedure with another NAV fix, run after run, it's been the same error. I'll continue to test and report back... I'd add a track but my mission is complicated with multiple scripts that are loaded externally from the MIZ, so not easy to share. But would love to hear comments on my expectations/techniques. Perhaps this is just the best it can do, but I find it odd if it's going to drift that badly that the error is in the same direction each time. I might be missing something here?