# FLATSIM: The ForM@Ter LArge-Scale Multi-Temporal Sentinel-1 InterferoMetry Service
## 4 Description of Products
### Time-Series Package  
This package corresponds to products generated at the time series inversion step (see Section 2.7). Map products are given in 8 (or 16) looks, in radar geometry and in ground geometry. Table 2 summarizes the time series products.  
* **DTs: time-series** This product is a data cube that contains the cumulated total phase delay images at each acquisition with respect to the first date. In practice, the reference is set to the origin of a linear fit through the time series for each pixel. This representation avoids for the APS of the first image to appear in negative on all other dates. Note, however, that it is not ideal in case of strongly non-linear deformation. The time series may be incomplete for some pixels and for some dates, and values are then replaced by NaN. We choose to deliver the total phase delay, that includes both residual atmospheric phase screens and displacement signals, without any attempt by us to separate both contributions. This allows the user to perform its own separation, possibly guided by his knowledge of the expected deformation signal properties. The geotiff file includes as many bands as time steps. The unit is in radians along LOS, positive away from satellite. Each band is named by the acquisition date. The associated preview file displays the cumulated displacement at the last time step.
* **MV-LOS: LOS velocity*
* The mean LOS velocity is given in a geotiff product with two bands:
* Band 1 is the mean velocity in rad/yr, positive away from satellite;
* Band 2 is a shaded view of the topography, with an illumination simulated to match the radar backscatter amplitude.
* **Net: Quality assessment product*
* This geotiff product gives various indicators of the quality of the time series inversion, provided in radar and in ground geometry.
* Band 1: RMS misclosure of the interferogram network for each pixel, in rad;  
\begin{table}
\begin{tabular}{l l} \hline \hline
**File Type** & **Description** \\ \hline DTs & Time series of total LOS phase delay (data cube) \\ MV-LOS & Mean LOS Velocity \\ Net & Auxiliary maps for the assessment of the time series quality \\ Stk-In & List of the interferograms file names \\ \hline \hline \end{tabular}
\end{table}
Table 2: Main timeseries products.  
* Band 2: Number of interferograms used in the time series inversion for each pixel;
* Band 3: Number of images used in the time series inversion for each pixel;
* Band 4: Proxy for the temporal coherence, computed as the norm of the average of all successive interferometric triplets (between 0 and 1);
* Band 5: Proxy for a possible bias in the timeseries, computed as the argument of the average of all successive interferometric triplets (in rad).
* **Stk-In: interferogram list product** It gives information on the timeseries, as for example the list of dates and interferograms used as input to the time serie inversion and the reference image that was selected.
* **Additional tt files** The \"RMSinterferro.txt\" and \"RMSdate.txt\" files, together with their png previews, are very useful to check possible problems on interferograms or on acquisitions. They provide the RMS interferometric network misclosure averaged either by interferogram or by date. For example, the RMS value for some interferograms will be large in case of uncorrected unwrapping errors. Specific errors associated with one image, for example in case of snow, strong atmospheric or ionospheric perturbations, or bad azimuth frequency modulation corrections, can also be detected.  
The zipped time-series package is about 6.7 Gb for 25 processed consecutive bursts (450 km long segment) and 100 processed images. The package size will increase linearly with the number of processed bursts and images. The data cube has a larger size in ground geometry (6.1 Gb, pixel spacing of 0.00111 degree) than in radar geometry (4.1 G, resolution of about 120 m).