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Distance Variable
Panayiotis Mousarris from United Kingdom  [20 posts]
12 years
Can anyone tell me what variable i should be using to estimate the distance to an object ?
John Christian from Norway  [25 posts] 12 years
You have to be more specific to describe what data you are using and which modules you are using. There is no "magic" distance calculation in it. You have to calculate this based on your image data somehow. For example you could estimate some distance based on the size of a blob if you know what the blob is, but it would not be very precise. You could use a laser or other rangefinder also to get some distance measurement.
Anonymous 12 years
If you also know that the object in on a planar (flat) floor you can loosely guage the distance by checking the Y coordinate of the object assuming the camera is pointed slightly down towards the floor. This is know as triangulation and can also be done with a laser light.

See YouTube for an example of someone using RR to do just that.

STeven.
Panayiotis Mousarris from United Kingdom  [20 posts] 12 years
Im tracking red square box blobs of fixed dimensions and using center of gravity module as my last filter. Till now i have been using the box size variable to estimate distance, until Steven told me that using the object size (ie. number of pixels) is more effiecient. I just can't figure out what variable I should be looking at. I guess it shoudl be located somewhere in the geometrical statistics module.
Anonymous 12 years
Panayiotis,

Add the Geometric_Statistics module. This will generate stats for the entire image. Then have a look at the AREA variable. That indicates the number of 'on' pixels in the image. This assumes that you have zeroed out the non-interesting parts of the image that you do not want to track. If you have multiple objects click on the Individual blobs radio button in the geometric stats module.

If your red square boxes are empty, i.e. they are just square lines use the FILL module with a 0 param to fill them in order to get a better AREA number.

STeven.

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