MODELING TASK DESCRIPTION
In order to place maps, shapefiles or any other data correctly in FEFLOW, FEFLOW offers the option to set the map projection at the beginning of the model construction. The map projection functionality of FEFLOW defines an overall model coordinate system, but at the same time allows to display all imported maps - whether they have the same or different coordinate systems - to their precise location. Depending on whether a model is built manually from scratch or from imported maps, the workflow to select the correct map projections is a bit different. Both ways are explained in the following article.
SOLUTION
Option #1 - Building a model from scratch
FEFLOW offers both local and global coordinate systems. Global coordinates represent for example absolute UTM coordinates whereas local coordinates are measured from a used-defined coordinate system origin, typically the lower left corner of a model domain.
In the domain definition dialogue starting a new FEFLOW model, the user first defines the local coordinate system - Fig. 1 (left image). While the extent is of secondary priority, it is essential to define the model coordinate system, which is the reference for all map projections later on during model construction. Only with a valid model coordinate system, the online maps are available in the Maps panel. The next step is to define the global coordinates origin to set the environment for the model domain - Fig. 1 (right image). It is good practice to use a pair of coordinates southwest of the planned model domain. These coordinates should be entered in correct UTM numbers.
Fig. 1 – FEFLOW domain definition dialogue indicating the selection of the the model coordinate system (left image) and the definition of the global coordinate origin (right image).
Once the model coordinate system and global coordinate origin is set, a model domain can be delineated using the FEFLOW polygon tool. All geometrical and parameter data generated during model construction adopts the model coordinate system and can be exported in the same projection. Imported datasets (e.g. K field, initial mass concentration, etc.) must contain the projection type. Shapefiles, for example, usually have an associated .prj file holding this information. Please note that for any tabular data files like .dat, .csv, .trp or similar ASCII formatted data, the UTM coordinates must align with the model coordinate system.
The model coordinate system can be changed later on from the menu /Edit/Map Projection/Select Map Projection.. Be aware that editing the reference coordinate system will most likely displace your already added maps from the Maps panel. Individual maps or datasets cannot be re-projected later on.
Option #2 - Importing maps to construct a model
When importing map files to define a model domain or to assign data to the model, FEFLOW requires the projection information of each map file to correctly localize the data. Shapefiles or other georeferenced data formats include the projection information. Again, FEFLOW requires one unique coordinate system for the model itself. When importing the first map file, FEFLOW automatically picks the associated coordinate system. The user can adopt this coordinate system or select a different one from the list - Fig. 2. Please note that only projected coordinate systems are available.
Fig. 2 – FEFLOW dialogue importing geometric data files and selecting a suitable coordinate system from the Map Projections list.
Any additional map files with different projections can be imported at any stage to the modeling project as long as the files are georeferenced. Such map files include data or parameter files, background raster maps or structural data (.dxf/.dwg files). Non-referenced files won't be displayed correctly and must be placed in a pre-processing step in any third-party GIS software. For a smooth workflow we recommend to always use the same coordinate system for all map files.
FURTHER INFORMATION & USEFUL LINKS
Manuals and Guidelines
FEFLOW 10.0 Documentation - Maps Panel
FEFLOW 10.0 Documentation - Working with Maps
FEFLOW 10.0 Documentation - Coordinates and Georeferencing