Selecting the Co-ordinate System

InfoWorks ICM has a default coordinate system that is used for all new networks (excepted when no map control is specified). The co-ordinates entered for network objects are assumed to relate to this system unless you specify otherwise.

Note: Automatic system allocation does not apply to databases without a map control (map control is set in the Options dialog). If you want to use web mapping services on such GeoPlans, it is necessary to select an online map projection system.

To change the coordinate system for an existing network:

1. Select Set coordinate system from the GeoPlan menu. The Select Coordinate System dialog or the Projected Coordinate System dialog, depending on the map control being used, is displayed.
2. Select the coordinate system to be used:
   • For ArcGIS Engine and ArcGIS Desktop map controls - click Browse and select a Projected Coordinate System from the standard Windows File Open dialog.
   • For a MapXtreme map control, InfoWorks ICM is supplied with a number of nationally-recognised coordinate systems from which you can select the required system:
     • Click to display the Choose Coordinate System dialog.
     • Select the desired projection system.
       Note: Although the coordinate system list for a MapXtreme map control includes 'Longitude and Latitude' options, these are geographic not projected coordinate systems and therefore should not be selected for use in InfoWorks ICM
     • Click OK. The Choose Coordinate System dialog closes and the name of the selected coordinate system is displayed in the Projection box.
   • For the ArcGIS Maps map control, there are a number of projected coordinate systems from which you can select the required system:
     • Click to display the Choose Coordinate System dialog.
     • Select the desired projection system.
       Note: The Choose Coordinate System dialog only lists projected coordinate systems that are compatible with the ArcGIS Maps map control.
     • Click OK. The Choose Coordinate System dialog closes and the name of the selected coordinate system is displayed in the Projection box.
3. If you choose Non-Earth coordinates, enter your projection system bounds. (These fields are greyed out for all other coordinate systems.) The maximum values for X and Y must be greater than the minimum values, and all values must be greater than zero.
4. If you want the selected system to become the default for all new networks, click Default and confirm that the coordinate system is to be used in future.
5. Click OK to apply the new coordinate system.

After changing the coordinate system, the coordinate values that have been entered for any existing network objects will remain the same, so the position of these objects on the background map will change to reflect the new system. You may then need to move existing network objects.

Tip: Note that you can change the coordinate system as soon as you have created a network, before adding any objects.

Using the Coordinate System for 2D Raster Export

When exporting 2D results to raster (TIFF), InfoWorks ICM uses the Alternative Coordinate System to determine the spatial reference of the exported image. The raster’s position, extent and pixel size are therefore controlled by the units and definition of the selected coordinate system.

If the Alternative Coordinate System uses non-metric linear units (for example, US Survey Foot or International Foot), InfoWorks ICM automatically applies the required unit conversion when generating the raster. This ensures that the exported raster is correctly geolocated and aligns with other GIS layers when opened in software such as ArcGIS using the same coordinate system.

For best results, ensure that the Alternative Coordinate System reflects the real-world coordinate reference system of your model area before exporting to raster.

See Exporting 2D to Raster for further details.

Geographic coordinate transformations

Copyright Statement - Portions of this computer program are owned by ESRI, Copyright © 2004 Environmental Systems Research Institute, Inc. All Rights Reserved.

When using ArcGIS Desktop/ArcGIS Engine as map control, geographic transformations can be specified to allow datasets which have different geographic coordinate systems to be mapped together.

Click the Geographic coordinate transformations Edit button on the Projected Coordinate System dialog to display the Geographic Transformations dialog.

Transformations available are those which are related to the current GeoPlan coordinate system. One transformation may be selected for each available coordinate system.

Transformations are saved as part of the coordinate system. Changing the GeoPlan coordinate system will clear all previously set transformations.

For information on how coordinate systems affect the Export 2D to Raster feature, see Exporting 2D to Raster.