The main Oasis display can be conceptualized as a set of map layers, such as is commonly used in Geographic Information Systems software. At the bottom is a base image, defining the region of interest and its projection. At the top is a layer where the user can annotate the image interactively. In between are any number of specialized drawing layers of the following types:
A separate Layer Control window (available through a button on the main window) allows the user to organize these layers and to edit appropriate information on each one. Area definition events (generated by the user interacting with the main display) are sent to all active layers (who will then respond appropriately for their data content).
The bottom layer of in the Oasis display is an image read from a FITS file. This layer can be manipulated using the Image Display tools.
An initial coordinate grid layer (corresponding to the system and epoch of the image) is added to the display when the first image is loaded. Others can be added using the Layers/Add Coordinate Grid menu item on the main window.
Coordinate grid attributes can be edited by selecting the grid layer on the Layer Control window and pressing the Edit button. A pop-up will let you change the grid's coordinate system and/or color. There is no limit to the number of overlaid grids layers that can be added.
When the display is zoom/panned, the grid remains fixed to the original image to maintain a stable position reference and to enable more rapid interactive zooming. A regridding button is provided on the main window to allow the user to change the grid overlay when the see fit.
Whenever a table is read into Oasis (e.g. through a catalog archive request or by reading in a table file), it is scanned for coordinates and added to the display as a table map layer (scaled symbols at the coordinates given).
Oasis can't always decipher which columns in the table should be used for what purpose, so the layer's display attributes can be edited by selecting it on the Layer Control window and pressing the Edit button. A pop-up will let you change the column name mapping to coordinates and the symbol size shape and color. Oasis imposes no limit to the number of overlaid source map layers that can be added.
Layer control also provides a Show Table button, which will bring up a window with a tabular table display. When the user selects a region, any active table display layers will search their data to find sources in the region and highlight them in the displayed table (and on the image through another event mechanism).
Conversely, if a set of records is highlighted in a table and Broadcast, those sources will be marked on the image display.
"Source" tables can actually contain information for drawing parameterized shapes (scaled circles, ellipses, boxes). In this case, the table file header must identify the kind of shape and the columns containing shape information (e.g. semi-major axis for ellipses).
Anyone wishing to use this functionality, which is still under development, should contact IRSA.
Oasis provides a mechanism for reading in generalized sky drawing (e.g. contour maps, region outlines, constellation drawings). This capability is based on a simple XML structure.
Oasis also provides a mechanism for generating such files, specifically the ability to create a contour map of the currently-displayed image.
Image collection information frequently comes in a tabular form (e.g. columns for positions, sizes, and references to the actual image data files) and Oasis provides special processing functionality for such data. This is a special case of the more general Sky Drawing capability.
Image metadata that is read in as a table will be scanned for geometric information (the equivalent of FITS header keywords CRVAL1, CRVAL2, CRPIX1, etc.), then added to the display as an image metadata table layer (outlines of the images).
The general Sky Drawing capability in Oasis can be used to draw static shapes on the sky. Focal plane outlines are different in that the location of the center and the angle of rotation on the sky must be treated as variables.
Oasis provides a general mechanism for drawing and moving such objects (Note: for the moment, only the SIRTF focal plane is available). For more information, see the Moveable Overlays Feedback discussion.
The main Oasis display can be conceptualized as a set of map layers, such as is commonly used in Geographic Information Systems software.
The Layer Control window (available through a button on the main window) allows the user to organize these layers and to edit appropriate information on each one. Area definition events (generated by the user interacting with the main display) are sent to all active layers (who will then respond appropriately for their data content).
The layer control window is organized as a table with one record for each layer. They layers each have toggles indicating whether they should be visible and whether they should respond to global settings like area definition events.
A table row (layer) can be selected, then either move around in the drawing heirarchy, deleted, "shown" (if there is another representation such as a tabular display), or edited. Editing takes different forms for each and is covered in the detailed layer-specific documentation.