Help Content > Import Data > Other Format > GPS

Purpose

It allows performing a filter on the temporal series and/or an under-sampling of the collected measurements.

The input data must have been previously imported.

Technical Note

This tool allows to perform two types of filtering:

•Low pass - it produces a smoothed temporal series.

•Linear Fit - it converts the input temporal series into point positions and related displacement velocities.

Additionally the number of measurements can be reduced (i.e. under-sampled) by keeping only those corresponding to the acquisition dates in the "Optional Input Files". This under-sampling is activated by entering at least one SAR image in slant range geometry in the "Optional Input Files". Images must be coregistered in case more than one image is inserted in the ''Optional Input Files'' panel.

The output data consist of an xml (SARscape GCP standard format) file. Moreover a kml (geographic LAT/LONG co-ordinates) and a shape file are generated.

If the "Optional Input Files" is entered (this is required when the under-sampling must be performed), the shape file is generated also in the slant range geometry of the first input and the points falling outside the imaged area are automatically removed. It must be outlined that the shape and kml files are only for visualization purpose.

The shape file is intended to be visualized by means of the Time Series analyzer; what is shown it is the measurement history (referred to the earliest measurement) along the vertical component; if the "LOS Time Series" flag is checked, the measurement history is displayed along the satellite line of sight (viewing geometry of the first file in the "Input file list"). In case only the Linear fit is selected, the output shape does not contain the temporal series to be visualized, the mean velocity value is retrieved from a linear fit of the displacement time series. It is a unique value of velocity averaged on the whole time series. If only the Low pass filtering is selected, it can happen that the input number of measurements are too many (more than 2000) for the shape to be visualized or for the output to fit in a single shape; is such case the use of an "Input file list" allows to under-sample the input series and to properly visualize the measurements in a single output shape file.

The output GPS shape files are used for visualisation purposes only and will not be used by any tool in SARscape. The names and the number of fields that characterize the attribute file (.dbf) of this shape file are created to be imported or used in the Modeling Tool. The time-series in the shape files show the absolute height value as default and the relative height respect to the first date, in case of re-projection in Line of Sight.

TIP:

•The low pass filter needs to be applied if the GPS time series shows a noisy pattern.

•The linear fit can be applied whenever the trend of the GPS time series is close to a linear trend. Doing so one will refine the results by removing only a constant value from the final output. The linear fit should be set to false if the GPS time series shows a non-linear trend, such as a sinusoidal one, and the user wants to transpose this trend onto the InSAR results. Furthermore the Linear Fit must be set to true when applying the GPS refinement in a DInSAR processing, as a single velocity value is required.

Input Files

Input file

Previously imported GPS series (.xml). This file is mandatory.

Optional Input files

Reference SAR images (_slc, _pwr), which are used for the under-sampling. This file list is optional.

Parameters - Principal Parameters

Low Pass Filter Size

Number of days to perform the smoothing. By entering the value 0, the filter is not executed.

Linear Fit

By setting this flag the linear fit filter is performed.

LOS Time Series

By setting this flag the time series of the shape files (.shp) is referred to the first input line of sight.

Parameters - Global

It brings to the general section of the Preferences parameters. Any modified value will be used and stored for further processing sessions.

Parameters - Other Parameters

It brings to the general section of the Preferences parameters. Any modified value will be used and stored for further processing sessions.

Output Files

Output file

Output file name of the processed data. This file is mandatory.

.xml

Xml file containing the processed data.

_slant.shp

Shape file (plus .dbf and .shx) containing the measurement history in the first input slant range geometry. This file is generated only if the "Input file list" is entered.

_geo.shp

Shape file (plus .dbf and .shx) containing the geocoded measurement history.

.kml

ASCII file containing the GPS points location in geographic co-ordinates. Double clicking on this file will automatically position the boundaries of the scene into the Google Earth environment.

Details specific to the Units of Measure and Nomenclature of the output products can be found in the Data Format section.

General Functions

Exec

The processing step is executed.

Store Batch

The processing step is stored in the batch list. The Batch Browser button allows to load the batch processing list.

The window will be closed.

Help

Specific help document section.

Specific Function(s)

None.

General Tools - GPS - GPS Filtering Undersampling

General Tools - GPS - GPS Filtering Undersampling