Setting the Coordinate System

Owned by Kester Scandrett
21 Sept, 2023
3 min read

With the release of EEMS 12.0, it is possible to revise the coordinate system (CS) of working projects. This feature is useful when the projection of an imported project is not specified correctly, resulting in inaccurate visualization and spatial analysis of gridded data. To view and modify the currently applied coordinate system, go to Model in the main toolbar and select Project Settings option (Figure 1). The Project Settings window, which accommodates three sections General, Default Precisions and Coordinate Projection, appears as shown in Figure 2.

Figure 1: Project Settings option

Figure 2: Project Settings window

Click on the Coordinate Projection section, and the currently applied or selected coordinate system is immediately presented in the window. As noted in the Warning: EFDC+ supports only Universal Transverse Mercator (UTM) and Geographic Projections. Any changes made will alter the projection of the model grid permanently, thus affecting multiple modelling functionalities.

To change the CS, click the Change button in the Projection Settings form.

The pop-up Coordinate System form (Figure 3) comprises the Specify a spatial reference section, which provides different CS options, and the Spatial Reference Information section, which details information of the currently selected CS. There are five reference coordinate systems as below:

  • Geographic (Longitude/Latitude): Selecting this applies the World Geodetic System (WGS) 1984 to the project.
  • UTM, Northern Hemisphere: Selecting this applies the Universal Transverse Mercator (UTM) - Northern Hemisphere projection. A drop-down menu will be enabled for the specification of UTM Zone (from 1 to 60).
  • UTM, Southern Hemisphere: Selecting this applies the UTM – Southern Hemisphere projection. Similar to the UTM, Northern Hemisphere, users need to select an UTM Zone for this CS in the second drop-down menu.
  • User Defined: Besides the predefined WGS 1984 geographic coordinate system and UTM projection, users can define their own UTM projection or import/download any projection for the current layer. Choosing this option enables the Define, Import, and Download
    • Define button: Defines projection by configuring the map projection parameters (Figure 4). The parameters are characterized based on the UTM and WGS 84 systems.
    • Import button: Defines projection by importing a CS information from a *.prj file (Figure 5).
    • Download button: Defines projection by downloading CS information with an EPSG Code (Figure 6).
  • No Projection: Selecting this means no projection will be applied to the entire project.

With all CS options, the Export button is always enabled, allowing users to retrieve projection details and save them in a *.prj file.

Once the desired projection is selected, click OK to apply changes to the project.

Figure 3: Coordinate System settings

Figure 4 shows a dialog that allows defining a UTM projection with some specific parameters. The scale factor of 0.9996 is applied for the zone width of 6° of longitude, and the scale factor of 0.9999 is applied for the zone width of 3°. The central meridian indicates the central meridian longitude of the zone. The latitude of the original is usually taken as zero, and the false easting is usually taken as 500 000 meters. The false northing is taken the zero value for the Northern Hemisphere and is taken the value of 10 000 000 meters for the Southern Hemisphere.

Figure 4: Define coordinate system with projection parameters based on UTM and WGS 84


Figure 5: Define projection by importing a *.prj file

Figure 6 shows a dialog that allows users to download projection information from the Internet using an EPSG code. EPSG codes for different CSs can be found at https://epsg.io or https://spatialreference.org. The EPSG codes for the projection information for UTM zones have the form EPSG:326xx. For example, the EPSG code for UTM Zone 10 is EPSG:32610, so users can enter the value of 32610 into the search box to download its projection information.

Figure 6: Define projection using EPSG Code