<< Click to Display Table of Contents >> Navigation:  Help Content > Interferometric Stacking > SBAS & E-SBAS > E-SBAS > Interferometric Stacking - SBAS - 5 - Geocoding

Purpose

 

The aim of this step is to generate geocoded products.

 

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. Pixels with a Precision (respectively "Height Precision Threshold" for the height related products and "Velocity Precision Threshold" for the displacement related products) higher than the specified thresholds, are masked out.

It is possible to move the entire SBAS_processing folder in another disk location without causing any problem in this step.

To analyze the results it is suggested to load the G_disp_geo_meta layer that contains different products, the full list is described in the output section of this page.

To get an overview of the displacement occurring in the area of interest, it is suggested load the G_SI_velocity_geo layer (contained within the G_disp_geo_meta layer), that corresponds to the second inversion mean displacement velocity expressed in mm/year in geographic region. Then the G_disp_geo_meta layer, allows to analyze the displacement time series of a single point; to do so it is necessary to use the Raster analyzer tool (while the G_disp_geo_meta layer is selected on the Layer Manager panel)

The output vector file (shape format) contains the following information:

•Displacement velocity measured in slant range direction (i.e. Line of Sight); this is related to the selected input model.

•Displacement measured on each date with respect to the oldest acquisition of the series.

•Total displacement integrated using the whole input temporal series (available only in the shape file).

•Coherence values. This is the multitemporal coherence which is proportional to the displacement trend fitting with the selected model.

•Pixel cartographic co-ordinates and height based on the Digital Elevation Model value corrected using the interferometric measurement

•Height correction with respect to the input Digital Elevation Model.

•Other ancillary information.

To analyze the displacement time series of a single point on the vector layer it is necessary to use the Vector analyzer tool.

It is worthwhile to mention that the output shape files can be too big for the visualization in the following cases:

•the number of points to represent in the output shape file is very large. In this case the "Shape Max Nr of Points" can be reduced.

•there are many acquisition dates (i.e. time series Input file list) and the time series related information are reported in the sha[e. In this case the "Generate Shape Time Series" flag can be de-selected.

When the real displacement direction is known for the whole scene, the resulting Line of Sight products can be reprojected along it obtaining the following file extensions:

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

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

•_SD, displacement values along the maximum slope direction, with the associated header files (.sml, .hdr).

•_UD, displacement values in the direction specified as azimuth and inclination degrees (i.e. custom direction), with the associated header files (.sml, .hdr).

•_VD, vertical displacement values, with the associated header files (.sml, .hdr).

 

To obtain the vertical and east-west component of the motion, it is necessary to process both ascending and descending geometry. The tools available to run the decomposition process are:

 

•Meta Combination, for raster products

•Shape Combination, for vector products.

 

It is warmly suggested to generate a displacement decomposition instead the re projection using ascending and descending configuration and the dedicated SARscape tool.

 

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.

 

Shape Mask File

The user can create a shapefile (.shp) that contains the area to discard, this shapefile must be geocoded (with the same carto-system of the reference DEM). The subsequent step will take this shape into account to remove the pixel inside the mask area from the geocoding step. This file is optional.

DEM/Cartographic System

 

Digital Elevation Model file

Name of the Digital Elevation Model 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, the following parameters are compulsory to define the Cartographic System:

 

State

Definition of the country or general projection systems.

 

Projection

Definition of the projection system of the selected State. In case that a general projection system is selected in State, the Projection is automatically set.

 

Ellipsoid

Definition of the ellipsoid. This is chosen according to the selected State and Projection.

 

Hemisphere

Definition of the hemisphere. This is chosen according to the selected State and Projection.

 

Zone

Definition of the zone. This is chosen according to the selected State and Projection.

 

Datum Shift Parameters

Definition of the datum shift parameters. These are chosen according to the selected State and Projection.

 

Reference Height

In case that the Digital Elevation Model is not used, a constant ellipsoidal height must be provided. Default Reference Height is 0.

 

Cartographic Parameters

The reference parameters for some projection systems (e.g. Stereographic, Polar Stereographic, Gnomonic, Mercator, Miller, Albers, etc.) can be set.

 

Principal Parameters

 

Rebuild All

This flag refers to all 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.

Height Precision Threshold

Upper threshold of the height measurement average precision values (refer to the Phase to Height conversion for more details). This must be provided in meters. This threshold is used together with the Velocity Precision Threshold and the Product Temporal Coherence Threshold for the masking process.

Velocity Precision Threshold

Upper threshold of the velocity measurement average precision values (refer to the Phase to Height conversion for more details). This must be provided in millimeter/year. This threshold is used together with the Height Precision Threshold and the Product Temporal Coherence 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.

Water Mask (dB)

Vale 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.

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.

Shape Max Number of Points

If values other than -1 are entered, the output shape file is split in several parts (each marked by a progressive numbering -_1; _2; etc.); each part of the shape contains a portion of the total number of points, which corresponds to the value entered. It is suggested not to exceed 200000 points to avoid visualization problems.

Generate Shape Time Series

By setting this flag the output shape file/s, with the displacement temporal evolution, are generated.

Generate Shape Counter Series

By setting this flag the output shape file/s, with the valid interferogram counter for each acquisition date, are generated. When the counter is zero, the correspondent acquisition date has been temporally interpolated. Higher the counter higher is the reliability of the corresponding estimated displacement measure.

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.

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.

Mean Window Size

The mean filtering of the output height raster image is carried out. The window filter size must be specified. If zero is entered, the mean filtering is not applied. This filter is applied after the execution of the interpolation steps.

Interpolation Window Size

The dummy values in the output raster file are interpolated. The interpolated value is the average of the valid values in a window of the size specified. If zero is entered, the interpolation is not applied; it is suggested to avoid setting this value to zero (refer to the Phase Unwrapping).

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.

 

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 - Displacement Projection

 

It brings to the  geocoding section of the Phase To Displacement Conversion and Geocoding 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(s)

 

Geocoding folder

Directory containing the following products:

•Due to the large number of output products meta (_meta). and series (.series).files are generated. They enable to load at once all relevant output products:

•The “raster” sub-folder with the products in raster version.

•The “vector” sub-folder with the products in shape version.

Generated meta and series files:

•G_model_geo_meta, which refers to the height, velocity plus ancillary layers, according to the choosen model during the first inversion, in the output cartographic projection.

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

•G_disp_geo_meta,  which refers to the height and displacement velocity measurements (plus ancillary layers) in the output cartographic projection, with atmospheric correction.

•G_interf_counter_geo_meta, which refers to valid measure counter for each acquisition.

The output results in “raster” folder consist of:

•displacement related products which are:

oG_FI_velocity_geo, corresponding to the first inversion mean displacement velocity [mm/year]. This raster is the result when G_SI_velocity_geo is not present.

oG_FI_acceleration_geo, corresponding to the first inversion mean displacement acceleration [mm/ year2]. This raster is the result when G_SI_acceleration_geo is not present

oG_FI_delta_acceleration_geo, corresponding to the first inversion mean displacement acceleration variation [mm/ year3]. This raster is the result when G_SI_delta_acceleration_geo is not present

oG_SI_velocity_geo, corresponding to the second inversion mean displacement velocity [mm/year].

oG_SI_acceleration_geo, corresponding to the second inversion mean displacement acceleration [mm/ year2].

oG_SI_delta_acceleration_geo, corresponding to the second inversion mean displacement acceleration variation [mm/ year3].

oG_SI_term_0_geo, corresponding to the zero-degree term of the second inversion polynomial [mm].

oG_SI_term_1_geo, corresponding to the first-degree term of the second inversion polynomial [mm/year].

oG_SI_term_2_geo, corresponding to the second-degree term of the second inversion polynomial [mm/year2].

oG_SI_term_3_geo, corresponding to the third-degree term of the second inversion polynomial [mm/year3].

oG_FI_V_precision_geo, corresponding to the velocity measurement average precision [mm/year] (refer to the Phase to Displacement conversion for more details).

oG_SI_DDDDDDD_X_disp_geo, corresponding to the date specific displacement [mm] measured with respect to the first acquisition date, to which a null displacement is assigned. Where DDDDDDDD is the acquisition date and X the incremental date ID.

oG_SI_DDDDDDD_X_disp_first_geo, corresponding to the date specific displacement [mm] measured with respect to the first acquisition date, to which a null displacement is assigned, without atmospheric removal. Where DDDDDDDD is the acquisition date and X the incremental date ID.

•general products which are:

oG_FI_H_correction_geo, corresponding to the first inversion correction [m] with respect to the input Digital Elevation Model. This raster is the result when G_SI_H_corretion_geo is not present.

oG_SI_H_correction_geo, corresponding to the second inversion correction [m] with respect to the input Digital Elevation Model.

oG_FI_H_precision_geo, corresponding to the height measurement average precision [m] (refer to the Phase to Displacement conversion for more details).

oG_FI_DEM, corresponding to the first inversion corrected Digital Elevation Model [m]. This raster is the result when G_SI_DEM is not present.

oG_SI_DEM, corresponding to the second inversion corrected Digital Elevation Model [m].

oG_SI_RMSE_mm_geo, which is a measure of the fitting quality geocoded. It is the RMSE [mm]. The higher this value the worse the fitting and inversion quality.

oG_SI_ DDDDDDD_X_interf_counter_geo, corresponding to the valid measures counter per each date.

oG_SI_interf_perc_geo, valid interferogram percentage.

oG_SI_image_perc_geo, valid acquisitions percentage (covered by at least one valid measure).

oG_SI_disc_counter_geo, disconnection counter (SBAS disconnected blocks disconnection counter).

oG_ALOS_geo, Azimuth Line of Sight. Positive angles are measured clockwise from the North; negative angles are measured counterclockwise from the North.

oG_ILOS_geo, Incidence angle of the Line of Sight. The angle is measured between the Line Of Sight and the vertical on the ellipsoid (flat earth).

The output results in “vector” folder consist of:

•G_vVdV_hHdH_cCdC_X.shp where VdV is the precision velocity threshold, HdH the height precision threshold, CdC the temporal coherence threshold and X the shape part id. Shapefile of the SBAS 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 Persistent Scatterers Parameters several shapefiles are created.  

work_geocoding folder

Directory used to store intermediate processing results.

Note: some outputs are created only if the respective flag is checked. Details specific to the Units of Measure and Nomenclature of the output products can be found in the Data Format section.

 

 

inversion

Directory containing the following products:

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

•The geocoded_model sub-folder with the products (final model) from SBAS inversion in cartographic co-ordinates.

•The geocoded_disp sub-folder with the products (displacements) from SBAS inversion in cartographic co-ordinates.

•The vector sub-folder with the shape files.

 

Naming convention for shape vector is _vVV_hHH_cC.C_X.shp where VV is the precision velocity threshold, HH the height precision threshold, C.C the temporal coherence threshold and X the shape part id.

 

work_inversion

Directory used to store intermediate processing results.

 

_ADF

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

 

_IDF

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

 

_SD

Displacement values along the maximum slope direction, with the associated header files (.sml, .hdr).

 

_UD

Displacement values in the direction specified as azimuth and inclination degrees (i.e. custom direction), with the associated header files (.sml, .hdr).

 

_VD

Vertical displacement values, with the associated header files (.sml, .hdr).

 

_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.

 

_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).

 

.shp

Shapefile of the SBAS 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 Persistent Scatterers Parameters several shapefiles are created. The file name is created as follows: SI_XX*_Y.shp where XX is the threshold for precision high, precision vel and coherence", 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 [mm/y]

▪RMSEmm: root mean square error of the final displacement model (derived from the displacement time series) [mm]

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

▪meanpwr: temporal average power

▪DEM: corrected ellipsoidal elevation [m]

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

▪Hprecision: estimate of the height measurement average precision [m]. It is computed considering the acquisitions spatial baseline distribution and the spatial coherence

▪Vprecision: estimate of the velocity measurement average precision [mm/year]. It is computed considering the acquisitions temporal baseline distribution and the spatial coherence

▪D_date: displacement acquisition date [mm]

▪imageperc: percentage of valid acquisitions (linked by in at least one valid interferogram)

▪interfperc: percentage of valid ingested interferograms (corresponding to SBAS inversion equations)

▪disccounte: number of time series disconnections (corresponding to the number of interpolated interruptions in the time series)

▪normL1: sum of absolute displacement time series values

▪ALOS: Line of Sight Incidence angle on Azimuth direction

▪ILOS:  Line of Sight Incidence angle on vertical direction

▪xpos:  cartographic coordinate based on the DEM reference system: x coordinate

▪ypos:  cartographic coordinate based on the DEM reference system: y coordinate

▪zpos:  cartographic coordinate based on the DEM reference system: ellipsoidal elevation [m]

 

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

 

 

Note: some outputs are created only if the respective flag is checked. 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.

 

Close        

The window will be closed.

 

Help

Specific help document section.

 

 

Specific Function(s)

 

None.        

 

References

 

None.