The Bounds only coordinate system operation is used to create a coordinate system file for maps when only the minimum/maximum XY-coordinates of the map boundaries is known. This type of coordinate system should only be used when there is no need or no desire to use projections at all. Note, maps using a coordinate system boundary only, cannot be transformed into any other coordinate system.
A new Bounds only coordinate system can be created via ILWIS-Python editor or can be directly created using ILWIS 4 user interface/create toolbox tab.
The required Python syntax to create a Bonds only coordinate system are:
name of the output coordinate system = ilwis.CoordinateSystem("")
Then, the Python syntax for the above mentioned create operation looks like example below:
cosys = ilwis.CoordinateSystem("code=proj=utm +zone=37 +ellps=WGS84 +units=m +no_defs")
The coordinate system can also be created using GPES number as it described bellow. The GPES codes are listed in ILWIS create projected coordinate system but also you can find them online: https://epsg.io/
If you use the epsg website, make sure choosing the code that has the compatible projection and datum/ellipsoid with the rest of your data. Information related to project 4 definition and epsg codes can also be derived online from: http://spatialreference.org/. The Python syntax for using epsg code looks like example below:
cosys = ilwis.CoordinateSystem("code=epsg:32736")
Once the coordinate system is created you can assign the minimum/maximum of coordinates to it by creating an envelope; it is not required, but optional. However, in case you decided to set the boundary coordinates make sure that the boundary is within the range of the coordinates derived from the EPSG or project 4 codes. The following Python syntax can be used to create an envelope:
name of the output envelope = ilwis.Envelope(ilwis.Coordinate(min/max coordinate of lower left corner),ilwis.Coordinate(min/max coordinate of upper right corner).
You may also use min/max coordinate of upper right and lower left coordinates as well. The Python syntax for creating an envelope looks like example bellow:
env=ilwis.Envelope(ilwis.Coordinate(696275.4000, 9797373.3700),ilwis.Coordinate(813775.4000, 9885123.3700))
The next step is to assign the envelope to the already created coordinate system using the following Python syntax: