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Action
on Trend
The Data Trend Treatment controls
how WinPICS handles trends in
your input data sets. The Action on Trend
allows
you to grid the modelled trend, the residuals, or the raw input data. The
entry under Modelling Trend With
describes the model to be used.
Select the Action on Trend by
clicking on the down arrow for the appropriate pull down menu in the Data
Trend Treatment area the Gridding
dialog box. There are five options:
- Default
– Fits a 2D 1st-order polynomial
curve (y = a + bx) to the input data to create a trend
model. The trend is removed from the data, the residual is gridded
and the trend is restored. (You will achieve the same results by choosing
Grid residual/Restore trend and
selecting "2d 1st - order polynomial" to Model the Trend With.)
- Grid residual/
Restore trend –Fits one of five mathematical
models to the input data for trend treatment. (2D 1st-order, 2nd-order,
3rd-order polynomial, mean value of data, or no action.) Select the model
from the drop-down
menu. The trend is removed from the data, the residual is gridded and
the trend is restored.
- Grid raw input
– Grids the raw input data without any trend treatment.
- Grid residuals
only – Grids and outputs the residuals. This is useful to quickly
view the difference between the input data values and the modelled trend.
- Output trend
only – Outputs the modelled trend only.
The residual is the difference between the input data values and the
modelled trend values at the same (x,y) location. Residual values will
be different for each gridding method.
Residual analysis of gridding without a trend model can be achieved
by selecting Mean value of input data
under the
drop-down. Residuals will be calculated as the difference from a flat
plane.
What do you want to do?