Help Content > Interferometric Stacking > PS & E-PS > 5

Purpose

The PS and E-PS products are geocoded and the displacements can be displayed in two kind of format: Shape and/or Raster according to the flag selected from the parameters.

In order to obtain reliable displacement measurements, one or more Ground Control Points (e.g. coming from GPS or other ground measurements) - "Refinement GCP file" - can be entered as input to the processing. This information is used to optimize the displacement trend assessment. In case only 1 GCP is selected, the correction will consist of a mean velocity constant offset, which does not have any spatial variation; if more GCPs are selected, the correction will consist of the best fitting calculated from all GCPs. The Ground Control Points must be provided in cartographic co-ordinates.

Technical Note

Refer to the Interferometry module for details.

The output results consist of geocoded products, which correspond to the outputs of both the step 1 and the step 2. These are:

•Ref_GCP_geo, shape file corresponding to the Reference Points of the highest MuSigma values (i.e. those used for the phase offset removal) automatically selected during the step 1.

•super_reference_gcp_geo, shape file corresponding to the best Reference Point of the highest MuSigma values automatically selected during the step 1.

•SubAreas_geo, shape file corresponding to the sub areas estimated according to the "Area For Single Reference Point" parameter.

•mean_geo, SAR Intensity average image and associated header files (.sml, .hdr).

•Meta files (_meta), useful to load at once the displacement velocity, the residual height, the coherence images and the date-by-date displacements (the latter only when the "Geocoded Raster Products" flag is checked).

•Meta files (_meta), with the displacement projected along the maximum slope direction (_SD) and on the vertical plane (_VD) (only if the respective flags are checked).

•"work" subfolder, where intermediate processing results are stored.

•PS/E-PS map and related information (PS/EPS_thrCohe_Id.shp and .kml), where thrCohe is the coherence threshold and Id is the shape index.

•Maximum slope direction values (_ADF), with the associated header files (.sml, .hdr).

•Maximum slope inclination values (_IDF), with the associated header files (.sml, .hdr).

•Azimuth Line of Sight (_ALOS) with the associated header files (.sml, .hdr). Positive angles are measured clockwise from the North; negative angles are measured counterclockwise from the North.

•Incidence angle of the Line of Sight (_ILOS) with the associated header files (.sml, .hdr). The angle is measured between the Line Of Sight and the vertical on the ellipsoid (flat earth).

general products which are:

•_geo_vel+height_meta, which refers to the height and displacement velocity measurements in the output cartographic projection.

•_geo_otherinfo_meta, which refers to the power mean, the multitemporal coherence, the height measurement precision and the corrected height measurements in the output cartographic projection.

•_geo_disp_first_meta, which refers to the date by date displacements, measured in the output cartographic projection, without atmospheric correction.

•_geo_disp_meta, which refers to the date by date displacements, after the atmospheric correction, in the output cartographic projection.

It is possible to move the entire PS_processing folder in another disk location without causing any problem in the further steps.

A graphic, showing the extracted displacement information, can be created using the General Tools>Vector analyzer, if Make Geocoded Shape is flagged (default), or General Tools>Raster analyzer, if Make Geocoded Raster is flagged.

Input Files

Auxiliary file

Reference file generated as output of the "Connection Graph" step and possibly updated afterwards. This file is mandatory.

Optional Files

Refinement GCP file

Shape or .xml file related to the GCPs used to assess the final result. This file is optional.

DEM/Cartographic System

DEM File

Name of the Digital Elevation Model (DEM) file. This should be referred to the ellipsoid. This file is optional. In case it is omitted, the ellipsoidal height and the relevant cartographic reference system, must be entered.

Output Projection

In case that the Digital Elevation Model is not used, it is mandatory to define the Cartographic System.

The Reset icon allows to reset the coordinate system field.

To use the same coordinate system as of another dataset, click the From Dataset button and select the source dataset.

To apply the same Coordinate System of the current selected layer, click the From Current View button.

Reference Height

In case that Digital Elevation Model is not used, a constant ellipsoidal height must be provided. The default reference height is 0.

Parameters - Principal Parameters

Product Temporal Coherence Threshold

Pixels with temporal coherence values smaller than this threshold will be set to dummy (NaN) as Persistent Scatterers in the final products.

Generate KML

By setting this flag the Google Earth .kml of the resulting PS is/are created. and the Upper/Lower limit of KML scaling parameters are activated

Upper Limit KML Scaling

The maximum expected displacement rate (integer value of the velocity in mm/year) is set (This field is only active if the Generate KML flag is set to True).

Lower Limit KML Scaling

The minimum expected displacement rate (integer value of the velocity in mm/year) is set (This field is only active if the Generate KML flag is set to True).

Make Geocoded Shape

By setting this flag the slant range products are geocoded onto the Digital Elevation Model cartographic reference system and the ultimate PS products are generated in vector format. By default, this option is flagged.

The Geocoded product can be projected along both the maximum slope direction (_SD), on the vertical plane (_VD) or a custom direction. The proper flag below must be activated.

Make Geocoded Raster

By setting this flag the slant range products are geocoded onto the Digital Elevation Model cartographic reference system and the ultimate PS products are generated in raster format.

The Geocoded product can be projected along both the maximum slope direction (_SD), on the vertical plane (_VD) or a custom direction. The proper flag below must be activated.

Make Slant Shape

By setting this flag the slant range products are generated in vector format. By default, this option is set to false.

Note: the output shape will be created inside the second inversion folder.

Refinement Stacking

The user can choose between the following options:

•Stack Velocity Disp Refinement.

•Stack Residual Height Refinement.

•Stack All Products Refinement.

The refinement process will be applied to the Velocity, to the Height or to both layers according to the chosen option. The refinement GCP file must be uploaded.

Refinement Radius (m)

Maximum buffer radius for the association of Ground Control Point with respect of the slant range unwrapped phase closer valid pixel.

Refinement Displacement Poly Degree

Degree of the polynomial used to estimate the displacement ramp, which will be removed from the input displacements date by date during the Re-flattening operation. In case this value is higher that the number of input Ground Control Points, it will be automatically decreased. The default values of 3 means that a displacement ramp in range and azimuth direction plus a constant displacement offset will be corrected. In case only the displacement offset correction is needed, the polynomial degree will be set to 1.

Rebuild All

By setting this flag the whole geocoding process is started from scratch.

It is advisable to leave this flag unchecked in case of process interruption, so that the products already generated have not to be computed and stored again.

Vertical Displacement

By setting this flag the displacements and velocity products are projected on the vertical direction.

Slope Displacement

By setting this flag the displacements and velocity products are projected along the maximum slope.

Displacement Custom Direction

By setting this flag any vector can be specified, in terms of azimuth (Azimuth Angle, measured in degrees from the North - clockwise direction) and inclination (Inclination Angle, measured in degrees from the horizontal plane). The map showing the displacement values projected on the specified direction is generated among the output products.

X Dimension (m)

The grid size of the output data in Easting (X) must be defined; the default unit of measure is meters.

Note that - for the Geographic projection - if values higher than 0.2 are entered they will be considered as metric units and then automatically, and roughly, converted from meters to degrees; if values lower than 0.2 are entered they will be considered as degree and used as such without any conversion.

Y Dimension (m)

The grid size of the output data in Northing (Y) must be defined; the default unit of measure is meters.

Parameters - Cluster

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

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 - Geocoding

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

Parameters - Displacement Projection

Stand by.

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.

Geocode using Mu/Sigma Threshold

If set to FALSE, only the coherence is used to geocode.

If set to TRUE, The MuSigma threshold is used beside the Product Temporal Coherence Threshold.

Mu/Sigma Threshold

This field is active only if Geocode using Mu/Sigma Threshold is set to TRUE.

Pixels with Mu/Sigma values smaller than this threshold cannot be kept as Persistent Scatterers.

Water Mask (db)

Value in dB used as threshold to retrieve a water body mask from the average intensity image. All the points under this threshold will be removed from the output layers. Active if smaller than 0.

Generate KML

By setting this flag the Google Earth .kml of the resulting PS is/are created. and the Upper/Lower limit of KML scaling parameters are activated

Generate KML Time Series

By setting this flag the temporal displacement will be generated date by date in kml format.

Max Points in KML

Maximum number of points in a single kml file to be considered, the size of each file depends on this value.

Generate Shape Time Series

By setting this flag the temporal displacement will be generated date by date in shape format.

Max Points in Shape

Maximum number of points in a single shapefile file to be considered, the size of each file depends on this value.

Note: Every single file that composes the shape file (shx, shp, dbf, etc...), must be smaller than 2 GB, if the size exceeds 2 GB two or more layers will be created.

Refer Output List to Older

By setting this flag the older acquisition will be set to zero displacement. The Reference will be considered as zero displacement otherwise.

Geocoding with Topographic Correction

If set to TRUE: each PS is geocoded with his topographic correction height (DEM + topographic correction from 2nd inversion).

If set to FALSE: each PS is geocoded using only DEM height (for example, in case of an accurate DEM).

Compute Precision

By setting this flag the velocity precision and height precision will be generated.

Smooth time series

This field corrects the time series by lowering too high values and augmenting too low values using the sensor wavelength. The default value of this flag is FALSE.

Output Files

geocoding

Directory containing the following products:

• files allowing to load the specific processing results (_meta).

• The "geocoded_dir" subfolder, which contains all processing results, in cartographic co-ordinates, which are loaded by means of the meta files.

.shp

Shapefile of the PSs with the associated files (.shx, .dbf and Google Earth .kml). If the number of points is larger than the "Shape Max Nr of Points" defined in the Preferences Common several shapefiles are created. The file name is created as follows: *_EPS/_PS_XX_Y.shp where XX is the decimal part of "Product Coherence Threshold" (0.XX), Y is an incremental number in case of more than one shapefile and * is the output root name chosen in the connection graph step.

Field description of the generated shape file:

▪velocity: mean velocity of the displacement for each pixel [mm/y]

▪coherence: multitemporal coherence, it is a quality index for the best fitting of interferometric phase date by date

▪MuSigma: it is a quality index, it is the mean/standard deviation ratio, where mean corresponds to a temporal mean

▪shp nbr: it corresponds the the number of statistical homogeneous pixels

▪Scatterer: it defines if a point is a PS or a DS

▪Hprecision: estimate of the height measurement average precision [m]. It is computed considering the acquisition spatial baseline, considering the multitemporal coherence

▪Vprecision: estimate of the velocity measurement average precision [mm/year]. It is computed considering the acquisition temporal baseline considering the multitemporal coherence

▪Range: pixel coordinate

▪Azimuth: pixel coordinate

▪SubArea ID: ID of the SubArea

▪lon/lat: geographic coordinates

▪xpos/zpos: cartographic coordinates based on the DEM reference system

▪zpos: corrected elevation (ellipsoid elevation), DEM reference heigth + Hcorrectio

▪Z: corrected geoid height, zpos - Hgeoid

▪ALOS: Line of Sight Incidence angle on azimuth direction

▪ILOS: Line of Sight Incidence angle on vertical direction

▪Hcorrectio: correction with respect to the input Digital Elevation Model [m]

▪D_date: displacement acquisition date in millimeters.

_ALOS

Azimuth Line of Sight with the associated header files (.sml, .hdr). Positive angles are measured clockwise from the North; negative angles are measured counterclockwise from the North. This file is created only if Make Geocoded Raster is selected.

_ILOS

Incidence angle of the Line of Sight with the associated header files (.sml, .hdr). The angle is measured between the Line Of Sight and the vertical on the ellipsoid (flat earth). This file is created only if Make Geocoded Raster is selected.

EPS/PS_disp_geo_XX_meta

This meta file is created if "Make Geocoded Raster" is selected. It contains three file called *_EPS/_PS_XX_cc_geo, *_EPS/_PS_XX_vel_geo, *_EPS/_PS_XX_height_geo (for coherence, velocity and height residuals). * is the output root name chosen in the connection graph step, while XX is the decimal part of "Product Coherence Threshold" (0.XX). In the meta file the _EPS/_PS_ALOS and _EPS/_PS_ILOS are also included. *_IDdate_XX_disp_geo files, which are the displacement for single dates, are also include; the IDdate identifies each single date image.

Note: To visualize the displacement time series of the ps.shp layer in ArcGIS Pro, it is necessary to perform the following steps:

➢right click on the shape file and select Enable pop-ups

➢right click on the shape file and select Configure pop-ups

➢in Configure pop-ups table select Chart/in Chart option select the Line Chart

➢set only the fields related to displacement, so the one as "D_date.."

➢go back to the Configure pop-ups

➢click on one point

➢the time series plot will appear

ADF

Maximum slope direction values, with the associated header files (.sml, .hdr). This file is created only if Make Geocoded Raster is selected.

_IDF

Maximum slope inclination values, with the associated header files (.sml, .hdr). This file is created only if Make Geocoded Raster is selected.

_SD

Displacement values along the maximum slope direction, with the associated header files (.sml, .hdr). This file is created only if Make Geocoded Raster is selected.

_VD

Vertical displacement values, with the associated header files (.sml, .hdr). This file is created only if Make Geocoded Raster is selected.

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

Please Note: the annotations of the geocoded files are displayed in ENVI View according to Preferences Common.

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.

Interferometric Stacking - Persistent Scatterers - 5 - Geocoding

Interferometric Stacking - Persistent Scatterers - 5 - Geocoding