InSAR dataset

InSAR dataset, in the modeling module, is a dataset of points stored in a shapefile (of the type Point or PointZ), with the following attributes:

•East - A numeric field with the east coordinates (UTM or Lat/Lon);

•North - A numeric field with the north coordinates (UTM or Lat/Lon);

•Elev - A numeric field with the elevation above the sea level, in meters; if a DEM is not supplied, values must be set to 0;

•Observed - A numeric field with the displacement sampled from the raster image; it has the same measurement unit of the raster image;

•Coef_east - A numeric field with the East cosine director of the Line-Of-Sight;

•Coef_north - A numeric field with the North cosine director of the Line-Of-Sight;

•Coef_up -A numeric field with the Up cosine director of the Line-Of-Sight;

•Sigma - A numeric field with the standard deviation of the InSAR points, in meters.

An InSAR dataset can be obtained through the Image Subsampling panel, with the sampling areas created with Sampling Areas panel, and raster files from an interferometric processing, (it can be created with any GIS software: when a shapefile is formatted according to the above attributes, it is automatically recognized as "InSAR dataset"). After running Non-Linear Inversion, Linear Inversion and Forward Modeling, other attributes are appended, with the processing results.

The cosine directors of the Line-Of-Sight can be used to combine the displacement in East, North and Up direction into the ground-satellite direction, through a linear combination:

DisplLOS = DisplEASTx Coef_east + DisplNORTH x Coef_north + DisplUP x Coef_up

where DisplLOS, DisplEAST, DisplNORTH and DisplUP are the displacement in the Line-Of-Sight, East, North and Up directions that can be obtained with Forward Modeling.

Further fields can be present in the InSAR dataset, according to the processing step.

After Non-Linear Inversion and Linear Inversion:

•N x [source_name] - Displacement, or velocity, due to each source [source_name] set for the inversion;

•Orbital - Displacement, or velocity, due to a constant offset or an orbital contribution (linear or quadratic surface);

•Modeled - Modeled displacement, or velocity, in the LOS direction, due to all sources and possible orbital contribution;

•Modeled_ea - Displacement, or velocity, in the east direction;

•Modeled_no - Displacement, or velocity, in the north direction;

•Modeled_up - Displacement, or velocity, in the up direction;

•Residual - Difference between Observed and the Modeled fields.

The measurement unit of the fields is coherent with the input data, i.e. is the same of East_obs, North_obs, etc...

There is no limit to the number of sources set in the inversion and an equivalent number of fields will be present in the output shapefile. Only one field Orbital is present, related to the specific InSAR dataset.

The original input shapefile is never changed; the processing creates a copy with the "_nonlinear" or "_linear" suffix, with the original attributes fields and the new ones added.

After Forward Modeling:

•N x [source_name] - Displacement, or velocity, due each source [source_name] set in Forward Modeling;

•Residual - Difference between the Observed and the Modeled fields;

•Modeled - Modeled displacement, or velocity, in the LOS direction, due to all sources;

•Forward_ea - Displacement, or velocity, in the east direction;

•Forward_no - Displacement, or velocity, in the north direction;

•Forward_up - Displacement, or velocity, in the up direction;

The measurement unit of the displacement is coherent with the source model, i.e. is in meters (meters/year in the case of velocity).

The original input shapefile is never changed: during the processing a copy with the suffix "_forward" is created with all the original shapefile fields and the new ones added.

Note: Forward Modeling can also carried out over a generic shapefile of points (geocoded); in this case only the Modeled_ea, Modeled_no and Modeled_up fields will be created.