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Creating a Field Definition

An image can be loaded in one of two ways, either by loading a local one from disk using the image display's toolbar, or by querying an image server, a large number of which are available through a drop-down menu. If querying a server, the image will be centred on the coordinates entered in the Forms Editor. These are indicated on the map by a green x-shaped cross which will move if the coordinates are changed.

At present, only FITS file with coordinates defined in the J2000 system are correctly handled. Therefore, you cannot use the Spatial Editor to set up pointings in Galactic coordinates. The OT will load the image, but the coordinates will not be displayed correctly. It is possible to use FITS files where the image is stored as a FITS extension, but the OT will only read the first, if multiple extensions exist.

Once an image has been loaded, if any pointings or a rectangle were previously defined in the Forms Editor, they will appear on the image and can be edited with the mouse. At the time of loading an image, the type of field definition must already have been chosen, either a rectangular area or multiple pointings (the latter by default). It is possible to change the definition using the Spatial Editor by clicking on the opposite definition on the toolbar i.e. by adding a single pointing when a rectangle has already been defined. A warning will be issued at this stage as the previous definition (size and orientation of rectangle, positions of all pointings) will be lost. As this implies, it is not possible to create a field definition that contains a mixture of single pointings and a rectangle.

An important part of the Spatial Editor is the ability to display the antenna beamsizes for each pointing, either for the 12- or 7-m antennas. For this to be possible though, the Representative Frequency must have already been defined in the Science Goal's Spectral Setup. Therefore, it is recommended that this section be completed before using the Spatial Editor.



Subsections
next up previous contents
Next: Single Pointings Up: The Visual Spatial Editor Previous: Overview of the Graphical   Contents
The ALMA OT Team, 2017 Dec 18