## 3 LiCSAR Products: Current State and Future Trend
### LiCSAR Products File Structure  
Figure 8 shows the LiCSAR system file structure hierarchy and naming convention. The blue parts represent the current state and the gray areas show the capabilities that will be available in the future. Starting from the top level, the LiCSAR products are categorised into 175 folders that correspond to the 175 orbital tracks per orbital cycle (relative orbits) of the Sentinel-1 satellites. Currently, a special folder EQ contains geocoded outputs of the LiCSAR EIDP system categorised according to the USGS ComCat code for each earthquake (an updated dissemination platform is an ongoing process). Figure 7: LiCSAR tectonic priority frames (ascending and descending) over the Alpine–Himalayan Belt and the number of interferograms processed by LiCSAR over active volcanoes as of April 2020. Global Active Faults data are from [61]. The naming convention of frame identifiers (used also as folder names for frame-related data) has a structure: OOOP_AAAAA_BBBBBB, where OOO denotes the number of the relative orbit, P identifies the orbital pass--either descending (D) or ascending (A), AAAAA is a colatitude identifier, i.e., a complementary angle of the latitude of the frame centre (multiplied by 100), and BBBBBB identifies the number of included bursts (three pairs of digits corresponding to number of bursts in each of three Sentinel-1 IWS swaths). Inside the frame directory, the generated InSAR products are located in the interferograms subfolder. The name of each interferometric pair shows the date of acquisition epochs used for that pair. The basic interferometric products reside in each interferometric pair folder as:  
Figure 8: The file structure of the LiCSAR system products publicly available in COMET LiCS portal. **yyyymmdd_yyyymmdd.geo.cc.tif**: coherence image (GeoTIFF) of the interferometric pair. The values vary between 1 and 255, where 1 refers to the lowest coherence values and 255 indicates the highest values of coherence. It is in uint8 format with 0 as the 'no data' value;  
**yyyymmdd_yyyymmdd.geo.cc.png**: a gray-scale raster preview of the coherence image (white = maximal coherence). The preview is resized to 30% of the original GeoTIFF;  
**yyyymmdd_yyyymmdd.geo.diff_pha.tif**: wrapped-phase spatially filtered differential interferogram image (GeoTIFF). The values vary within the range of -\(\pi\) to \(\pi\) radians. The phase values pertain to the the satellite LOS, thus the signal can be interpreted as motion away from the satellite if the observed phase difference is positive. The phase values are saved in the file in a float32 precision with 0 as 'no data' value;  
**yyyymmdd_yyyymmdd.geo.diff_unfiltered_pha.tif**: wrapped-phase interferogram image (GeoTiFF). The only difference between this and the previous image is that the phases are not spatially filtered;  
**yyyymmdd_yyyymmdd.geo.diff.png**: a raster preview of the wrapped-phase interferogram (a colour fringe in the direction blue-green-yellow-orange-purple-blue would mean a change of 2\(\pi\) radians towards the satellite). The preview is resized to 30% of the original GeoTIFF;  
**yyyymmdd_yyyymmdd.geo.unw.tif**: unwrapped phase image in radians (GeoTIFF). Keeping the same rule as the wrapped phase images, the values are in the satellite LOS direction, i.e., positive values mean a range increase (i.e., motion away from from the satellite), while negative values mean a range decrease (i.e., motion towards the satellite) perhaps caused by uplift. The format of the file is float32 with zero values as 'no data' often related to pixels which are masked due to low coherence;  
**yyyymmdd_yyyymmdd.geo.unw.png**: a raster preview of the unwrapped interferogram, representing interferometric phase values after rewrapping to a scale of 6\(\pi\) per colour cycle (using the same convention for LOS direction as for the wrapped-phase interferogram preview).