Documentation.

README.md

 # RegionChooser
 
-[RegionChooser](https://transfer.hft-stuttgart.de/gitlab/hft_gitlab/regionchooser) is a Java project. Its graphical interface allows to extract a specific region from [CityGML](https://www.ogc.org/standards/citygml) and save it as a smaller CityGML file.
+[RegionChooser](https://transfer.hft-stuttgart.de/gitlab/hft_gitlab/regionchooser) is a Java project. Its graphical interface allows to extract a specific region from multiple [CityGML](https://www.ogc.org/standards/citygml) files and save it as a smaller CityGML file.
 
 ![RegionChooserScreenshot](region_chooser_screenshot.png)
 
@@ -30,6 +30,52 @@ You first need to run SimStadt in order to select a [repository](https://simstad
 * `./RegionChooser.sh` in Linux
 * `./RegionChooser.command` in macOS
 
+### Select a region
+
+* Once a repository has been imported, a map should be shown with the convex hulls of the available CityGML files.
+* It is possible to define a polygon by clicking repeatedly on the map.
+* If an intersection is found with at least one CityGML file, a list of files will be shown on the right.
+* The selection might intersect multiple files. The user can select the desired files.
+* By clicking on `Download Region`, a new CityGML file will be created, by merging the intersections of the polygon with each selected CityGML file.
+
+### Get coordinates of polygon
+
+The coordinates of the currently drawn polygon can be exported to [WKT](https://en.wikipedia.org/wiki/Well-known_text_representation_of_geometry) by clicking on `Copy coordinates`. It can be useful for further processing, e.g. in a Python script.
+
+As an example:
+
+> POLYGON((9.176194 48.779168, 9.171473 48.775265, 9.176923 48.772890, 9.179842 48.774474, 9.181043 48.774134, 9.183103 48.775661, 9.182073 48.776962, 9.176194 48.779168))
+
+## Command-line
+
+RegionChooser can also be called from the command-line:
+
+```bash
+Launching RegionChooser CLI --help
+Usage: region_chooser [-hlV] [-e=31467] -o=output.gml -w=polygon.wkt -i=input.
+                      gml[,input.gml...] [-i=input.gml[,input.gml...]]...
+Extracts a region from one or more citygmls.
+  -i, --input=input.gml[,input.gml...]
+                            Citygml files to extract from
+  -o, --output=output.gml   Output file
+  -e, --epsg=31467          EPSG id for coordinate reference system.
+                            Will use the one from input.gml if unspecified.
+  -l, --local               Are WKT coordinates in local CRS?
+                            Coordinates are in WGS84 if unspecified.
+  -w, --wkt=polygon.wkt     File containing WKT polygon, or - for stdin
+  -h, --help                Show this help message and exit.
+  -V, --version             Print version information and exit.
+```
+
+As an example:
+
+```bash
+java -classpath "Desktop\SimStadt_0.10.0-SNAPSHOT_master_20221019_7d2546f\lib\*"
+     eu.simstadt.regionchooser.RegionChooserCLI
+	 --input Grombühl.proj\LoD2_32_566_5516_2_BY.gml,Grombühl.proj\LoD2_32_568_5516_2_BY.gml,Grombühl.proj\LoD2_32_570_5516_2_BY.gml
+	 --output Grombühl.proj\Grombühl.gml --wkt "POLYGON((9.920858224863567 49.807325539080495, 9.918540796274696 49.79447295986074, 9.992612680429975 49.79358644932381, 9.991926034922162 49.807325539080495, 9.920858224863567 49.807325539080495))"
+```
+
 ## Development
 
 In order to compile, test and install RegionChooser into your local Maven repository: