5 Calibrating Raster Images
65
Polynomial
5th degree
21
22
Polynomial
6th degree
28
29
Surface
Splines
3
not applicable
To choose a calibration method
Select a calibration method from the
Calibration method
list of the
Calibration
dialog
box.
Estimating Calibration Accuracy
Calibrating transforms the entire raster image by means of the calculated
transformation. All image points, not only those defined in calibration pairs,
generally move. Accuracy estimation allows for the expected displacement of every
raster point to be found for the calibration method chosen, without having to run the
calibration procedure.
For every calibration pair, estimating creates one more point called
estimated
. It
shows the position of a
measured point
after running the chosen calibration method.
Markers of such points are colored yellow. (The markers of real points are blue; the
markers of measured points are red. Change these default colors in the
Preferences Dialog Box). The program then calculates and displays the distances
between each estimated point and its appropriate real point. These distances define
calibration deviations for each pair.
WiseImage calculates the parameters of the chosen method so after
transformation, each
measured
point
is placed as close to its appropriate
real
point
as possible. WiseImage only uses
Control
and
Grid
calibration pairs for these
calculations.
To estimate the displacement of a certain image point after calibration, create a
calibration pair with the measured and real points that have coordinates of the
desired image point, and assign the
Check
type to this pair. The pair will not be
considered when defining transformation parameters, but the program will find the
estimated point for the pair and calculate deviation relative to its real point location.
To estimate the calibration accuracy
1.
Create the calibration pairs needed to eliminate the distortion of your image.
2.
Specify the locations of the measured point.
3.
If needed, then create Check pairs to decide on the arbitrary points’
movements.
4.
Select the required method from the Calibration method list.
Base the choice on recommendations given above in "Choosing Calibration
Method” on page 63. Note that WiseImage only allows the use of those
models applicable to the specified set of calibration pairs. Estimation cannot
be run if these requirements are not met.
5.
Press the
button in the Calibration dialog box.