Help Content > Interferometric Stacking > SBAS & E-SBAS > E-SBAS > 4

Purpose

The E-SBAS 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 the step 3. 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.

•ESBAS map and related information (ESBAS_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 E-SBAS_processing folder in another disk location without causing any problem in the further steps.

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

Either a previously created Ground Control Point file (.xml) is loaded (Load GCP File) or the interface to create a new Ground Control Point file is automatically loaded (Create GCP File, refer to the "Tools>Generate Ground Control Point" for details). This file is used for manual refinement. This file is optional.

DEM/Cartographic System

DEM File

Digital Elevation Model (DEM) file name. This should be referred to the ellipsoid. In case a list of input files is entered, the DEM must cover the whole imaged area. This file is optional.

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.

Principal Parameters

Product Temporal Coherence Threshold

Pixels with coherence values smaller than this threshold will be considered as DS, pixels with coherence values higher than this threshold will be classified as PS.

Generate KML

By setting this flag the Google Earth .kml of the resulting ESBAS 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 Raster

By setting this flag the output raster file/s are generated.

Make Geocoded Shape

By setting this flag the output shape file/s are generated.

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 inversion folder.

Rebuild All

This flag refers to all E-SBAS process. By setting the flag the whole process is performed from scratch (if not incremental mode is active). 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.

Geoid Type

EGM96

Earth Gravitational Model 96.

EGM2008

Earth Gravitational Model 2008.

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 Residual Phase Poly Degree

Degree of the polynomial used to estimate the phase ramp, which will be removed from the input unwrapped phase 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 phase ramp in range and azimuth direction plus a constant phase offset will be corrected. In case only the phase offset correction is needed, the polynomial degree will be set to 1.

Vertical Displacement

By setting this flag the displacements and velocity products are projected on the vertical direction. Do not use the reprojection if the real displacement direction is unknown.

Slope Displacement

By setting this flag the displacements and velocity products are projected along the maximum slope. Do not use the reprojection if the real displacement direction is unknown or when the reference DEM resolution is poor with respect to the process results.

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. Do not use the reprojection if the real displacement direction is unknown.

Azimuth Angle

Custom Direction Azimuth Angle measured in degrees from the North - clockwise direction.

Inclination Angle

Custom Direction Inclination Angle measured in degrees from the horizontal plane.

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.

Process_str

This parameter does not have any impact on the processing chain.

Product Temporal Coherence Threshold

Lower threshold of the temporal coherence measurement values. This threshold is used together with the Height Precision Threshold and the Velocity Precision Threshold for the masking process..

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.

Product Temporal Coherence Threshold

Lower threshold of the temporal coherence measurement values. This threshold is used together with the Height Precision Threshold and the Velocity Precision Threshold for the masking process.

Product Temporal Coherence Threshold

Lower threshold of the temporal coherence measurement values. This threshold is used together with the Height Precision Threshold and the Velocity Precision Threshold for the masking process.

Generate KML

By setting this flag the Google Earth .kml of the resulting E-SBAS 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).

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 KML Time Series

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

Make Geocoded Shape

By setting this flag the slant range products are geocoded onto the Digital Elevation Model cartographic reference system and the ultimate E-SBAS 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 E-SBAS 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.

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 E-SBAS pixel is geocoded with his topographic correction height (DEM + topographic correction from 2nd inversion).

If set to FALSE: each E-SBAS pixel 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.

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.

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.

E-SBAS Resampling Method

By setting the relevant flag, the interpolation method is specified.

Nearest Neighbour

Bilinear Interpolation

3rd Order Cubic Convolution

4th Order Cubic Convolution

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.

Date String prefix in dbf file

The prefix 'D' or 'D_' can be specified for the date in the dbf file.

Geoid Type

If the Geoidal DEM is selected the Geoid Type among the EGM96 , EGM2008 or user defined model can be selected.

geoid_file_name

This field allows the user to use a previously imported Geoid (the Geoid import tool is named User Geoids Management). The estimated height values will be referred to the selected Geoid.

Output Files

geocoding

Directory containing the following products:

• 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 E-SBAS pixels with the associated files (.shx, .dbf and Google Earth .kml). If the number of points is larger than the ''Max Points in Shape" field value several shapefiles are created. The file name is created as follows: *_ESBAS_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

▪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 + Hcorrection

▪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.

ESBAS_disp_geo_XX_meta

This meta file is created if "Make Geocoded Raster" is selected. It contains three file called *_ESBAS_XX_cc_geo, *_ESBAS_XX_vel_geo, *_ESBAS_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 ESBAS_ALOS and ESBAS_ILOS are also included. *_IDdate_XX_disp_geo files, which are the dispacement for single dates, are also include; the IDdate identifies each single date image.

The other raster geocoded files (_vel_geo, _height_geo, _cc_geo et...) are saved under the path _ESBAS_processing\work\work_geocoding.

Note: To visualize the displacement time series of the esbas.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 - SBAS & E-SBAS - E-SBAS - Geocoding

Interferometric Stacking - SBAS & E-SBAS - E-SBAS - Geocoding