# Kitty’s measuring up

Did some simple testing to determine the camera angle, resolution and suitable dual laser dot separation.  Kitty was sat on a stool, looking up at the ceiling, and I was waving the laser around the ceiling watching the curses display.  The picture below is upside down!

```           U______________
∧      ^      ^
/|\   21cm     |
/ | \____V      |
/  |  \        205cm
/ α |   \         |
/    |    \        |
/     |     \       |
/______|______\______V
|<----170cm---->|```

U = camera position
Span of kitty laser dot detection = 170 x 170cm
Test height (camera to ceiling) = 205cm
Alpha = atan(170 / (2 x 205) = 22.5°

Camera height at takeoff = 21cm
∴Camera span at takeoff = 17.4 x 17.4cm
Image size = 32 x 32 pixel
∴Image resolution at takeoff = 0.5 x 0.5cm
Landing leg separation = 23cm

Based on the above, 2 dots spaced by 15cm would make a good laser leash

Image span at 1m hover = 82 x 82cm
Double dot separation viewed from 1m = 15cm / 82cm x 32 pixels ≅ 6 pixels

So minimum capture resolution of 32 x 32 pixels should be fine for 1m hover, but by 2m, the risk of merged dots is too high as they’ll only be 3 dots apart.

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