Banner PresencePLUS P4 COLOR Series - Manual (Page 186)

where A is the area, (x
c
, y
c
) are the coordinates of the centroid and (x
i
, y
i
) are the coordinates of pixel i. These values
represent the variance with respect to x, the variance with respect to y, and the covariance, respectively. The final
results can be calculated as follows.
The table below gives a more practical perspective on how to interpret these results. If the camera is configured to
convert pixels to other units, the major and minor axis lengths will be given in those units. The major axis angle is
always given in degrees.
Meaning of Major Axis
angle Meaning of Minor Axis
Length Meaning of Major Axis
Length Blob Shape
unstable equal to the major axis
length diameter of the circle circular, no holes
orientation of the ellipse width of the ellipse length of the ellipse elliptical, no holes
unstable equal to the major axis
length diameter of a circle that best
approximates the square square, no holes
orientation of the rectangle width of an ellipse that best
approximates the rectangle length of an ellipse that best
approximates the rectangle rectangular, no holes
orientation of the
shape-unstable if length and
with are nearly equal width of an ellipse that best
approximates the shape length of an ellipse that best
approximates the shape complicated shape, no holes
results vary depending on
exact shape-experiment on
your particular shape results vary depending on
exact shape-experiment on
your particular shape results vary depending on
exact shape-experiment on
your particular shape any shape with holes
Banner Engineering Corp. Minneapolis, MN USA 186
2/2010 PresencePLUS Software Tools