Coordinate Systems

The topics below discuss how Mira works with the coordinate systems of images and plots.

World Coordinate System	describes the FITS World Coordinate System.
Image Coordinate System	describes how coordinate systems are used for measuring distances, angles, centroid positions, and other quantities in images.
Pixel Coordinate Definition	describes how pixels are referenced and counted in image coordinates.
Subpixel Coordinate Definition	describes how fractional pixels are counted in image coordinates.
Angle Measurement Definition	describes how angles are measured for different coordinate systems.
Plot Coordinate Systems	describes how coordinate systems are used in displaying 1-D data.
Plotting in World Coordinates	describes how 1-D plots implement the image coordinate system.
Image Display Orientation	describes how rows are counted in different image formats.
FITS Image Orientation	describes how FITS format images are oriented for display.
Image Coordinate Display	describes real-time readout of the image pointer (crosshair).
Adjusting the Image Cursor	describes how to adjust and position the image cursor.
World Coordinate System Keywords	describes header keywords used to describe world coordinate systems.
Delete WCS	Deletes any type of World Coordinate System scale from the image, reverting it to the (column,row) system.
WCS Keywords	Lists the values of world coordinate system keywords in the image header.

The topics below discuss tools used for calibrating and working with world coordinate systems


Astrometric Calibration	creates a "plate solution" for an image using the coordinates of at least 3 marked stars.
Set Arcsecond Scale	assigns an arcsecond scale to an image.
Set Equatorial Scale	assigns a simple equatorial coordinate system of (right ascension, declination) to an image.
Set Linear Scale	assigns a linear coordinates scale to the image. The same scale is applied in both coordinates.
Set Linear Coordinate Units	assigns linear world coordinate units to each axis. The units may be different in each axis. For example, the image may be a radio astronomy image with flux versus time or a numerical simulation showing a 2-D map of velocity versus density.
Set X-Axis Linear Format	Configures the X world coordinate displaywhen the X coordinate is calibrated in linear units.
Set Y-Axis Linear Format	Configures the Y world coordinate displaywhen the Y coordinate is calibrated in linear units.
Go To Coordinates	Moves the image cursor to a target position, or loads the current position in either pixel or world coordinates.