Point Measurements

The Point Measurement tool measures a collection of point coordinates and values on an image. In addition to reporting the pixel value, or "luminance", the pixel coordinates are reported in both (column,row) and world coordinates if the image has a world coordinate calibration. The coordinates are marked using the mouse crosshair or may be precision centroid coordinates computed near the clicked point. This command is like the Centroid measurement affiliated with the Image Cursor except this command operates from a toolbar and the the points are persistent until you leave the Points mode by closing the toolbar. This command allows many points to be drawn on the image whereas the centroid marks only one point at a time . Results are reported in the Points Measurements Pane. The toolbar opens in Marking Mode (top button) active. Marker properties are set in the Marker Properties dialog opened from the button on the Points toolbar.

To activate the Point Measurements toolbar, click on the Image Tools Toolbar or use Measure > Points command on the main menu.

The following picture shows an Image Window with several points marked on the image. Notice the Point Measurements Toolbar docked on the left border of the Image Window.

The 3 points marked above creates a Points Measurements Pane and lists the measurements in it.

Procedure

First, make sure Point Measurement command.

First, be sure the Drawing and Centroiding properties are set as desired. To open the Marker Properties dialog, click on the toolbar.
If Marking Mode is not active, click the button on the window toolbar (not the Image Tools Toolbar).
Move the mouse pointer to each target point and click the left mouse button.
Repeat for each target point on the image.
To move an existing point, click on the Points toolbar to enter Move mode, then drag a marker to a new position and drop it there. If centroiding is enabled in the Marker Properties dialog, the marker will automatically centroid on near the point where it is dropped.
If points are no longer needed, click to enter Delete mode and click on the points to remove them.
To track marked points through an image set, click on the toolbar.
To re-enter marking mode, click on the toolbar.
To disable all toolbar modes for Point Measurements, click on the Image Toolbar or select Disable Modes from the Image Context Menu.

Measurement Results

Measurements are tabulated in the Points pane as shown above. Using this window, the measurements may be sorted, rearranged, saved to the clipboard or a file, etc.

If the image has a World Coordinate System ("WCS") calibration and the Centroid First Point box is checked in the Point Properties dialog , then (X,Y) is a centroid position computed from the centroid (column,row) position.

The items in the Report are described in the table below.

Point Measurements
#	The sequence number of the measurement.
Image	The name of the image that was measured
Distance	The distance in pixel units, or arcseconds if the image has a WCS calibration.
Index	By default, Mira fills this column with a sequential number which is the index of the point starting at 1. However, unlike the # column, which cannot be edited, this entry can be edited to give the point any identifier which then would be included in a saved or copied report.
X	The X coordinate of the point in world coordinates. If no world coordinate calibration exists, the value is the column position.
Y	The Y coordinate of the point in world coordinates. If no world coordinate calibration exists, the value is the row position..
Value	The value of the pixel at (X,Y).
Col	The column coordinate of the point.
Row	The row coordinate of the point.

Procedure

Measurement Results

Related Topics