Derivation:

x1 = 309px
x2 = 128px
x1' = 15"
x2' = 0"

Z ~ Avg(35",39") = 37"

dx = x1 - x2 = 309px-128px = 181px
dx' = x1' - x2' = 15" - 0" = 15"

C = dx/dx' = 181px / 15" = 12px/inch

dx' = dx / C
dx' = dx / 12

This equation works only at Z = 37"
If we double the distance to 74"
Each pixel corresponds to more inches
dx' = 2 * dx / 12

So, for the general equation

dx' = (Z/37") * dx / 12


General equation

dx' = (Z/37") * dx / (12px/in)
dx' = Z * dx / (12*37)
dx' = Z * dx / 444

Validate Equation

dx' = Z * (x4-x3) / 444
dx' = 60 * (420-323) / 444
dx' = 60 * 97 / 444
dx' = 13"

dx' = x4'-x3' = 15"-0" = 15" ~ 13" Check

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Data Points:

World Coordinates

	Point 1
		Blue
		zDistance	0
		x		0
		y		0
	Point 2
		Black
		zDistance	0
		x		-15"
		y		0
	Point 3
		White
		zDistance	14"
		x		0
		y		0
	Point 4
		Red
		zDistance	14"
		x		-15"
		y		0
	Point 5
		Blue
		zDistance	0
		x		0
		y		-10"
	Point 6
		Blue
		zDistance	0
		x		-15"
		y		-10"


Screen Coordinates Cam 1 (RGB)

	Point 1
		Red		51
		Green		40
		Blue		72
		x		382px
		y		256px
	Point 2
		Red		5
		Green		0
		Blue		6
		x		274px
		y		233px
	Point 3
		Red		147
		Green		127
		Blue		120
		x		420px
		y		209px
	Point 4
		Red		34
		Green		0
		Blue		0
		x		323px
		y		201px	
	Point 5
		Red		0
		Green		1
		Blue		6
		x		384px
		y		334px
	Point 6
		Red		7
		Green		5
		Blue		16
		x		278px
		y		311px	


Screen Coordinates Cam 2 (Depth)

	Point 1
		zDistance	153-1.3*81=48"
		x		180px
		y		130px
	Point 2
		zDistance	153-1.3*77=53"
		x		120px
		y		120px
	Point 3
		zDistance	153-1.3*74=57"
		x		215px
		y		100px
	Point 4
		zDistance	153-1.3*69=63"
		x		155px
		y		095px	
	Point 5
		zDistance	153-1.3*78=52"
		x		180px
		y		180px
	Point 6
		zDistance	153-1.3*73=58"
		x		125px
		y		160px