How to create dem file for a seies of islands using dem.py?

[A1b8]

Hi all,
When I used dem.py to generate dem file for islands, it doesn't work well. I find the code defines some non-existent DEM zip files, and these areas are located only over the sea, which has led to the DEM being unable to stitch normally.
Of course, I can generate dem using other softwares (e.g., arcgis). But I don't know how to edit the *vrt and *.xml files.

If someone could help me solve this problem, I would be extremely grateful.

[LiangcaiQiu]

First, I hope I understand your question correctly. I suggest you run 'dem.py --help' to view the configurable parameters, then you will find there is a '-f (--filling)' option ( -f, --filling: Flag to instruct to fill missing Dems with null values (default null value -32768. Use -v or --filling_value option to change it)), which can help you fill in the area without dem data.
Here is an example:

dem.py -a stitch -b 21 23 119 126 -r -s 1 -c -f

You can try it, the program can run normally and stitch out the dem data of the target area. I hope it helps, and I wish you all the best

[user@xxxx InSAR_Dir]$ dem.py --help
usage: dem.py [-h] [-a ACTION] [-c] [-m META] [-s SOURCE] [-f] [-v FILLINGVALUE] [-b BBOX [BBOX ...]] [-p PAIRS [PAIRS ...]] [-k] [-r] [-l] [-d DIR]
              [-o OUTPUT] [-n UNAME] [-w PASSWORD] [-t TYPE] [-x] [-u URL]

options:
  -h, --help            show this help message and exit
  -a ACTION, --action ACTION
                        Possible actions: stitch or download (default: stitch).
  -c, --correct         Apply correction EGM96 -> WGS84 (default: False). The output metadata is in xml format only
  -m META, --meta META  What type of metadata file is created. Possible values: xml or rsc (default: xml)
  -s SOURCE, --source SOURCE
                        Dem SRTM source. Possible values 1 or 3 (default: 1)
  -f, --filling         Flag to instruct to fill missing Dems with null values (default null value -32768. Use -v or --filling_value option to change it)
  -v FILLINGVALUE, --filling_value FILLINGVALUE
                        Value used to fill missing Dems (default: -32768)
  -b BBOX [BBOX ...], --bbox BBOX [BBOX ...]
                        Defines the spatial region in the format south north west east. The values should be integers from (-90,90) for latitudes and (0,360)
                        or (-180,180) for longitudes.
  -p PAIRS [PAIRS ...], --pairs PAIRS [PAIRS ...]
                        Set of latitude and longitude pairs for which --action = download is performed. The values should be integers from (-90,90) for
                        latitudes and (0,360) or (-180,180) for longitudes
  -k, --keep            If the option is present then the single files used for stitching are kept. If -l or --local is specified than the flag is
                        automatically set (default: False)
  -r, --report          If the option is present then failed and succeeded downloads are printed (default: False)
  -l, --local           If the option is present then use the files that are in the location specified by --dir. If not present --dir indicates the directory
                        where the files are downloaded (default: False)
  -d DIR, --dir DIR     If used in conjunction with --local it specifies the location where the DEMs are located otherwise it specifies the directory where
                        the DEMs are downloaded and the stitched DEM is generated (default: ./)
  -o OUTPUT, --output OUTPUT
                        Name of the output file to be created in --dir. If not provided the system generates one based on the bbox extremes
  -n UNAME, --uname UNAME
                        User name if using a server that requires authentication
  -w PASSWORD, --password PASSWORD
                        Password if using a server that requires authentication
  -t TYPE, --type TYPE  Use version 3 or version 2 SRTM, or nasadem
  -x, --noextras        Use this flag if the filenames do not have extra part
  -u URL, --url URL     If --type=version2 then this is part of the url where the DEM files are located. The actual location must bethe one specified by --url
                        plus /srtm/version2_1/SRTM(1,3).If --type=version3 then it represents the full path url