Line Measurements

The Line Measurement tool measures the distance between two points and the angle of the line connecting them. The results are reported in the Lines Report window, which has all the built-in functionality of a Report Window. The Distance & Angle command operates from a Window Toolbar, which opens with Marking Mode active.

• To activate the Line Measurement tool, click on the Main Toolbar or click Lines in the Measure menu.

• View a Procedure.

• The screen capture below shows two lines marked on an image. The resulting measurements are reported in a Report window, as shown further below.

  

  Measurement Results

  Measurements are tabulated in the Lines window as shown below (this shows the two measurements made for the image above). The Lines window is a Report Window with built-in functionality for sorting, rearranging, copying, saving, and other actions. Multiple images may be measured as an image set or by opening the Line Measurement Toolbar for multiple image windows. All measurements are reported in the same Lines window

  

  Measurements for all objects in all images and all Image Windows go into a single Report window. If you want to clear the window of prior measurements, make sure the Report window has focus, then use the View> Clear menu command.

  The items in the Lines report are described in the table below. The last 4 columns, which list the row and column coordinates of the endpoints, are not shown in the screen image above.

  Line Measurement Quantities

  #	The sequence number of the measurement.
  Image	The name of the image that was measured.
  Index	The marker index for the particular image.
  Distance	The distance in pixel units, or World units if the image has a WCS calibration. If the image has an angular calibration, such as in astronomical images, this is in arcseconds.
  Angle	The angle in degrees. If the image has a world coordinate calibration in angular units, such as an astronomical image, this is a Position Angle.
  X 1	The X coordinate of the starting point.
  Y 1	The Y coordinate of the starting point.
  Value 1	The image pixel value at the starting point.
  X 2	The X coordinate of the ending point.
  Y 2	The Y coordinate of the ending point.
  Value 2	The image pixel value at the ending point.
  Col 1	The column coordinate of the starting point.
  Row 1	The row coordinate of the starting point.
  Col 2	The column coordinate of the ending point.
  Row 2	The row coordinate of the ending point.

  Marking Endpoints

  As with other interactive marking commands, the Distance & Angle command can use the exact marked endpoints or it can compute either or both of the endpoints as a precise centroid position. All 4 combinations of centroid or no centroid and starting point or ending point are possible. To set this option, click on the toolbar to open the Marking Preferences dialog for this command, then select the Centroid page.

  The related Distance & Angle measurement tool marks one line on a single image per window, however the general operating principles are the same. The topic Examples of Distance & Angle Measurement discusses the issues of centroiding the starting and ending points when making a line measurement.

  Related Topics

  World Coordinate System, Angle Measurement Definition, Measuring Images, Report Windows, Marking Preferences