Coordinate Systems


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

Coordinate System Topics

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.

 Coordinate Commands

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.

Related Topics

Contents, Measuring Images