<< Click to Display Table of Contents >> Navigation:  Help Content > Interferometry Module > Displacement Modeling > Interferometry - Displacement Modeling - Forward Modeling

Purpose

 

This panel can be used to generate the surface displacement, geocoded or in slant range geometry, in a raster or vector format, generated by one or more input sources.

An example involving this panel can be found in the tutorial.

 

Technical Note

 

Forward modeling is used to generate the surface displacement due to any combination of geophysical sources, in a geocoded or slant range geometry, with output in a raster or vector format; the Forward Options folder allows to set the type of output.

For a raster format, the user must specify extent, resolution and coordinate system of the displacement maps; they can be manually specified or set equal to an image file already existing (several file formats are allowed). When a SARscape slant range image is used as reference, the output is generated in slant range, with line-of-sight displacement in radians, wrapped or unwrapped (for slant range output a DEM is mandatory). When multiple sources are supplied as input, the output raster will contain the cumulative effects of all the sources.

In the case of geocoded output, East, North and Up components of the displacement are produced in three different files; they can be then combined into a Line-of-Sight, and optionally wrapped, with the Project Raster to LOS panel.

For a vector format, a reference shapefile of points must be supplied and the forward calculation is performed for every point. It can be a generic shapefile of points, an InSAR dataset or a GPS dataset: : the cumulative displacement of all the sources and that of every single source are stored as different shapefile attributes. For InSAR, the east, north and vertical components are automatically projected into the line-of-sight, using the cosine directors stored in the shapefile attributes.

The INPUT Sources folder allows to create, recover and setup the sources used to model the geodetic data. Three sources are available: Elastic dislocation source, used to model the surface displacement induced by a uniform dislocation for a rectangular source in an elastic and homogeneous half-space [Okada, 1985]; Point pressure source, used to model the surface displacement induced by an expanding or compressing point-source [Mogi, 1958]. The "Edit..." button must be used to properly set the source(s); Nuclear explosion  (based on Mogi) to model the displacement induced by an underground nuclear explosion.

 

In this panel the use of the XML Project File is mandatory

 

INPUT Sources

 

ADD SOURCES

 New

         Elastic Dislocation (Okada): open the panel to set the parameters of an elastic dislocation/opening

         Point Pressure (Mogi): open the panel to set the parameters of a point volume source

         Nuclear Explosion (based on Mogi): open the panel to set the parameters of a point source calculated in kilotons

 Import

         From Shapefile: add a source from an InSAR or GPS shapefile

         From XML Project File…: retrieve a source from an existing XML Project File

EDIT SOURCES

 Edit parameters…: set the source properties through a source dependent panel

 Remove: remove the selected source(s) from the list

VIEW SOURCES

 Plot 2D: open a Graphic Viewer to see the source in a geocoded map; for a non-linear source, two items are drawn, corresponding to the minimum and maximum values.

 Plot 2D – Frontal View (fault only): open a Graphic Viewer to see the best fit sources in the fault coordinates (strike/dip)

Plot 3D:  open a  Graphic Viewer to see the best fit sources in 3D

EXPORT SOURCES

 Save to shapefile…: allow the user to save the sources in a shapefile

 

Options

 

Forward Model Output

Raster

Set the output in raster format.

DEM

A DEM file required only when a SARscape slant range file is set as reference raster or when at least one of the sources has the option “Compensate for topography”.

 

Set raster info...

Allow to set the output resolution, extent and Cartographic System. The raster extent can be also defined graphically around the source(s).

 

Reference raster...

Allow to get the raster parameters from an existing image, geocoded or in slant range geometry.

 

Output Unit

The measurement unit of the output raster image: m, cm, mm for geocoded images; Phase, Complex for slant range images.

 

Output File Root Name

Name of the output file root. According to the output type, a different suffix is appended

 

Vector

Set the output in vector (shapefile of points) format.

 

Reference shapefile

Allow to select a shapefile of points (see the Technical Notes)where the predicted displacement is calculated.

 

Output Unit

The measurement unit of the output data: m, cm, mm

 

 

XML Project File section

 

New...

Create a new XML Project File content into the panel.

 

Open...

Open the XML Project File content into the panel.

 

Save

Save the XML Project File content from the panel.

 

Save as...

Save the XML Project File content from the panel defining the project name.

 

Close

Close the XML Project File content from the panel.

 

Output(s)

 

forward_east

For geocoded raster output, the east component of the displacement

_forward_north

For geocoded raster output, the north component of the displacement

_forward_up

For geocoded raster output, the vertical component of the displacement 

_forward.shp

For vector output, the point vector shapefile with the modeled points stored as attributes

_sint

Line-of-sight, slant range raster file with Phase as output unit

_dint

Line-of-sight, slant range raster file with Complex as output unit

 

General Functions

 

Start        

Start of the processing.

 

Cancel        

The window will be closed.

 

Help        

Specific help document section.

 

Specific Function(s)

 

None.

 

References

 

None.