What is the right measurment of seating position of lounge chair??  

Which lounge chair?
Or are you just asking in general terms?

All depends
If you're the designer you should be figuring out which measurments work best for you. If you're asking about a specific chair those measurments vary. Some chairs are as low as 10" some as high as 18"

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I usually carry a tape measure wherever I go and measure anything that I like, there is no correct measurement. I think a lot of mid-lower end manufacturers have been getting things wrong for some time, I find almost all open framed 'danish' style armchairs or the hard moulded and upholstered polyurethane swivel chairs more comfortable than the padded boxes available now.
Many furniture manufactures supply cad files of their chairs.

also consider that comfort...
also consider that comfort is dependant on age. Many people find it hard to sit down on and get out of a very low chair, especially if there are no armrests. If You are young You might not find that for yourself.
I remember a photo of a designteam that constructed sort of a research-chair that had an adjustable seat-pad and back to determine the "right" angles and height. But if You are a designer I guess there's plenty of literature (with examples) on seating positions as well.

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it might seem obvious too but remember that with a lot of heavily foamed chairs the actual seating height could be as much as 3-6 inches lower when sat in, good point about age and generally you might want to consider obesity too, an office near my work has a row of Eames towers bases and theyre looking quite diminutive relative to the many larger people sitting in them.
One thing you could do is take a large piece of cardboard and trace the profile (if its a 2 dimensionally curved chair, like say an Aalto). The profile alone is not the design, you could save yourself a lot of work by standing on the shoulders of years of knowledge.

One is
far more likely to be able to specify the correct seating height and angles for a dining (so-called "side") chair, than for a lounge chair. Many different postures of semi-reclined seating are comfortable for the average human body; one aspect (as mentioned) is the ease or difficulty with which one can remove oneself from the chair. Chair arms are a decided advantage in this regard. . .

how about sprung loaded eject...
how about sprung loaded ejection seats? BOING!,

How about...
A Craftmatic adjustable?
It even comes with a free camera!

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now thats a machine for sitting in, though I expect Corbu would have rather sat on razor blades.
It might be an idea (depending on your design) to buy an old office chair with gas lift and back levers and all those doo-dahs, pull it apart and just use the mechanism as a testing device.