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Purpose

 

It is intended to represent the fields of a shape (dbf) file, with different colors.

 

It is typically adopted for the Persistent Scatterers or the SBAS shape results.

 

Technical Note

 

The graphic representation can be created as follows:

1.Open a geocoded file in the ENVI view.

2.Open, from "File/Open Vector File" (ENVI main menu command bar)/ shape file; this must have been generated with the same areal extent and geographic projection of the geocoded image (point 1).

3.Launch the "Time Series Vector Analyzer" program, select the relevant .shp file and load it in the same display of the geocoded raster file.

4.By clicking the "Multicolor" button, in the "Vector Analyzer" interface, you are prompted to specify the attribute to display. It is possible to modify the display parameters such as the Min/Max displacement values for the color scaling.

5.Locate the mouse and click the left button; then push the "Plot Time Series" button ("Vector Analyzer" panel) in order to display the relevant graph.

 

Plot information dedicated to interpolation option

Once the Set Temporal Interpolation Code In Time Series is set to True in geocoding results (Other Parameters), the interpolation options can be displayed.

A pop-up is displayed which suggest to set the ENVI Preferences is displayed if the have never been set before. File/Preferences/Plots/Symbol has to be set. By default the interpolation symbol is displayed in red.

TS Vector Analyzer/Plot Time Series is now active using interpolation information.

By clicking Option/Show Interpolated Values, the interpolation properties are activated.

The red point shows the the temporal interpolated values. If all the points are displayed in red, all the corresponding dates have been spatially interpolated.

The intepolation method includes refinement and atmosphere estimate contributions. Please, make sure the reference point used in the refinement is not affected by noise, otherwise an unexpected behaviour is shown.

 

Specific behaviors when a Reference Point is selected.

 

 

The selection of a Reference point influence the behavior of the output result.

With reference to the figure above where:

 

Figure a) shows the point differential average velocities when two different reference points are selected.

b) Original relative result time series (left) and absolute time series (right) once the reference point selection allows the re-flattening process. The noisy pick on the reference point time series (in green) shows the noise propagation in the velocity computation of the red point, once the reflattening is performed.

c) Original relative result time series (left) and absolute time series (right) the reference point selection allows the re-flattening process. The noise which characterizes the blue point used as reference point in this figure shows random picks on the reference point time series. The noise propagation in the velocity computation of the orange point, once the reflattening is performed, shows the corresponding propagated random behavior on the orange time series.

 

 

Please note: In case of large datasets, such as results of a PS processing, the results is split into several shape files. Right click on the correct shape file on the layer manager on the left side of ENVI and then select "active layer" before plot the data with the Time Series Analyzer".