What are the Position objects x y z readout in?

[DoctorNo]

Project: I'm looking to create fire effect from dropping napalm. (teaser sample below)
I cannot figure out what the the values are in.
what is unitpos.x.z  and unitpos.x.x mean? is this the x value in accordance to x plane?
As far as the negative value ... should I just assume velocity and some others should just be absolute value?
What is the x, y, z values associated to? I assumed environment grid coords that we routinely convert lat, long to x,y.
Problem is it doesn't seem to change much when I change it's location so I'm not sure what it's correlated to.
What does get unit:getPosition() then?
So i have time t, position (x, y, z) ... where z is height, heading in -pi to pi radians?, pitch in angle for x.y
quadratic equation, y = -9.81x^2 + height

Edited August 28, 2022 by DoctorNo
Adding in more detail

[DoctorNo]

 

Here are my final equations that I'll try, just posting this in case someone wants to chime in that it should be different. I'll test it anyway.
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Napalm Bomb Impact Calculation: Math Complexity: Quadratic Function, Basic Algebra, Geometry
Main Problem:
Known:
drop_position x1, y1, z1, t1
drop_height = z1
drop_time = t1
drop_velocity x1, y1, z1

Desired: impact_position = x2, y2, z2
 

Final Calculated: (broken into x, y, z components)
x2 = x1pos + x1vel(t2-t1)
y2 = y1pos + y1vel(t2-t1)
z2 = (-9.81)(t2-t1)^2 + z1vel*(t2-t1) + z1

Note: -9.81 is gravity m/s^2 ... we need grid units...
- due to this, we need to conduct a true experiment with only 1 unknown variable ... gravity in grid units.
- let's setup an experiment, drop smallest bomb possible and accurately hit a target.
With this we will get drop event (x1, y1, z1) and additional hit event for the ground unit (x2, y2, z2).
- let's deal with wind and other factors later

Side Problem:
Known: Solve for g --> gravity in grid units
z2 = (g)t^2 + z1vel(t2-t1) + z1
g = ((z2 - z1) - z1vel(t2-t1)) / ((t2-t1)^2)
Now plug g back in to Final Calculated above and solve for x2, y2, z2
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