Documentation | Help File | UI | 2D Mode | Menu | File | Coordinate Systems

Clicking on the File/Coordinate Systems menu item provides the means for setting the coordinate system for the Map area, i.e., the coordinate system in which all layers of an open map project are displayed. This menu item invokes the Coordinate System and Coordinate System Setup dialog boxes (pictured below) with settings to select or custom define the map area coordinate system. Changes to the map area coordinate system settings are instantaneously reflected on the map display.

Before considering the Coordinate System and Coordinate System Setup dialog boxes, it is important to understand that in many situations the software intelligently anticipates the coordinate system. In these situations, the user need not use the map area coordinate system settings, because the program:

• Automatically reads (if available) the coordinate system of each layer, looking for coordinate system information embedded natively in the layer and in external coordinate system files (PRJ, World, TAB registration, TRN file) associated to the layer. The program understands thousands of coordinate systems for all supported layer formats.
• Automatically applies the coordinate system of the first-opened layer as the map area coordinate system.
• Automatically reprojects the display of any layers (vector, image, grid) in other coordinate systems to the map area coordinate system. Layer reprojection is efficient and performed and on-the-fly.

The incidence of the Coordinate System and Coordinate System Setup dialog boxes opened from the File/Coordinate Systems menu relate only to the map area coordinate system. These same dialog boxes are also called by other functions elsewhere in the program that can require a coordinate system selection for another purpose:

• Export menu, to specify the export coordinate system (if different than the coordinate system of the source layer).
• New menu, to specify the coordinate system when creating a new (empty) vector layer (if different than the current map area coordinate system).
• Options dialog dialog box, to set the target coordinate for a layer rectification job (if different than the map area and the reference layer coordinate systems).
• Layer Layer Properties dialog box (under the Layer tab), to edit or apply coordinate system information for a layer.

For situations that do require the user to specify a coordinate system (for the map area or another purpose), there are two methods:

1. Select a predefined coordinate system from the thousands of predefined coordinate systems presented in the Coordinate System dialog box. The coordinate systems are organized into two drop-down lists: Projected systems reflecting linear units (meters, kilometers, miles, feet…) and Geographic systems reflecting angular units (degrees, radians, grads). Because the lists are long, a handy  search tool is built in. Type in the name of a coordinate system, or just a few letters of the name, and the coordinate system is quickly found. This method is easiest and recommended.
2. Manually (custom) define a coordinate system using the parameter settings presented in the Coordinate System Setup dialog box, which is invoked by clicking on one of the … buttons in the Coordinate system dialog box. The Coordinate System Setup dialog box provides settings to custom define a projected or geographic coordinate system, including 150+ projections, 900+ datums, linear and angular units, Easting, Northing, etc. (The built-in search tool also works for the projection and datum lists.) Manual coordinate system definition is more complicated and necessary only for unusual or advanced situations.

Coordinate System dialog box for selecting a predefined coordinate system.
Full description of this dialog box is available at Coordinate System.

The program must know the coordinate system of each layer to properly display the layer in the map area coordinate system, with correct scale, rotation, and distance representations. If a layer without a recognized coordinate system (because information is missing, incomplete, or the layer does not reflect a coordinate system) is opened, the program notifies that the layer is without a coordinate system and presents the option to rectify (rotate, scale, skew, warp, and georeference) the layer to a coordinate system. (Refer to the Rectify help topic for more on rectification.) In the rare case that a layer reflects a coordinate system that is known to the user, but the coordinate system information is incomplete or missing from the layer, an advanced user can edit the layer coordinate system information within the Layer Properties dialog box (with changes saved to the project file) - instead of using the rectifying tools to georeference the layer to a coordinate system.

To choose a predefined projected (reflecting linear units) coordinate system

1. Click on the File/Coordinate Systems menu item - this invokes the Coordinate System dialog box.
2. Within the Coordinate System dialog box, click on the Projected system option.
3. Pick the coordinate system from the Projected system list. (TIP: Use the built-in search tool by just entering in the field a few letters of the coordinate system name.)
4. Click on the OK button.

To choose a predefined geographic (reflecting angular units) coordinate system

1. Click on the File/Coordinate Systems menu item - this invokes the Coordinate System dialog box.
2. Within the Coordinate System dialog box, click on the Geographic system option.
3. Pick the coordinate system from the Geographic system list.  (TIP: Use the handy search tool to quickly find a coordinate system from the list. Just type in the field a few letters of the coordinate system name.)
4. Click on the OK button.

To custom define a projected coordinate system

1. Click on the File/Coordinate Systems menu item - this invokes the Coordinate System dialog box.
2. Within the Coordinate System dialog box, click on the Projected system option.
3. Click on the … button on the right hand side of the Projected system option - this invokes the Coordinate System Setup dialog box.
4. Within the Projection System tab of the Coordinate System Setup dialog box, define the coordinate system using the provided settings.
5. Click on the OK button.

To custom define a geographic coordinate system

1. Click on the File/Coordinate Systems menu item - this invokes the Coordinate System dialog box.
2. Within the Coordinate System dialog box, click on the Geographic system option.
3. Click on the … button on the right hand side of the Geographic system option - this invokes the Coordinate System Setup dialog box.
4. Within the Geographic System tab of the Coordinate System Setup dialog box, define the geographic system using the provided settings.
5. Click on the OK button.

To save a projected coordinate system to a file

1. Click on the File/Coordinate Systems menu item - this invokes the Coordinate System dialog box.
2. Within the Coordinate System dialog box, click on the Projected system option.
3. Click on the … button on the right hand side of the Projected system option - this invokes the Coordinate System Setup dialog box.
4. Within the WKT tab of the Coordinate System Setup dialog box, click on the Export button - this invokes the Save As dialog box.
5. Within the Save As dialog box, go to the drive on which you want to save the file.
6. Enter the folder in which you want to save the file.
7. Enter a name for the file in the File name field.
8. Click on the Save button - this brings back the Coordinate System Setup dialog box.
9. Within the Coordinate System Setup dialog box, click on the OK button - this brings back the Coordinate System dialog box.
10. Within the Coordinate System dialog box, click on the OK button.

To load a projected coordinate system from a file

1. Click on the File/Coordinate Systems menu item - this invokes the Coordinate System dialog box.
2. Within the Coordinate System dialog box, click on the Projected system option.
3. Click on the … button on the right hand side of the Projected system option - this invokes the Coordinate System Setup dialog box.
4. Within the WKT tab of the Coordinate System Setup dialog box, click on the Import button - this invokes the Open dialog box.
5. Within the Open dialog box go to the drive on which the file is stored.
6. Enter the directory which contains the file.
7. Double-click on the file - this brings back the Coordinate System Setup dialog box.
8. Within the Coordinate System Setup dialog box, click on the OK button - this brings back the Coordinate System dialog box.
9. Within the Coordinate System dialog box, click on the OK button.

To save a geographic coordinate system to a file

1. Click on the File/Coordinate Systems menu item - this invokes the Coordinate System dialog box.
2. Within the Coordinate System dialog box, click on the Geographic system option.
3. Click on the … button on the right hand side of the Geographic system option - this invokes the Coordinate System Setup dialog box.
4. Within the WKT tab of the Coordinate System Setup dialog box, click on the Export button - this invokes the Save As dialog box.
5. Within the Save As dialog box go to the drive on which you want to save the file.
6. Enter the folder in which you want to save the file.
7. Enter a name for the file in the File name field.
8. Click on the Save button - this brings back the Coordinate System Setup dialog box.
9. Within the Coordinate System Setup dialog box, click on the OK button - this brings back the Coordinate System dialog box.
10. Within the Coordinate System dialog box, click on the OK button.

To load a geographic coordinate system from a file

1. Click on the File/Coordinate Systems menu item - this invokes the Coordinate System dialog box.
2. Within the Coordinate System dialog box, click on the Geographic system option.
3. Click on the … button on the right hand side of the Geographic system option - this invokes the Coordinate System Setup dialog box.
4. Within the WKT tab of the Coordinate System Setup dialog box, click on the Import button - this invokes the Open dialog box.
5. Within the Open dialog box, go to the drive on which the file is stored.
6. Enter the directory which contains the file.
7. Double-click on the file - this brings back the Coordinate System dialog box.
8. Within the Coordinate System Setup dialog box, click on the OK button - this brings back the Coordinate System dialog box.
9. Within the Coordinate System dialog box, click on the OK button.

To turn off the map coordinate system

1. Click on the File/Coordinate Systems menu item - this invokes the Coordinate System dialog box.
2. Within the Coordinate System dialog box, click on the Turn off (unknown system) option.

• To convert and save a vector layer in a different coordinate system, use the Export feature.
• To georeference (rectifying if necessary) a vector or raster (image, grid) layer to a coordinate system, use the Rectify feature.
• To verify or change the coordinate system information for an individual vector layer, use the Layer/Layer Properties feature.

• TatukGIS coordinate system naming reflects OGC (OpenGIS) WKT definitions and EPSG codes.
• Projected coordinate systems are based on a map projection (Mercator, Mollweide, Robinson, Albers, Stereographic…) reflecting linear units (meters, kilometers, miles, feet…). Geographic coordinate systems are based on angular units (degrees, radians, or grads). The degrees based WGS84 coordinate system used for GPS is a good example of a geographic coordinate system.
• If the map coordinate system is turned off, each opened layer is displayed in its own coordinate system and any layers not in the same coordinate system will not be displayed correctly together in the same coordinate space.
• Though the TatukGIS on-the-fly reprojection performance is extremely efficient, best map rendering performance can be realized when all layers and the map area are in the same coordinate system, so that on-the-fly reprojection is not required. This eliminates the use of computational resources to perform reprojection calculations.