Triton Isis - Manual (Page 88)

June 2004 Isis® Sonar User's Manual, Volume 2
78
To measure the distance between two logged contacts, display
both contact images and use the left trackball button to drag out a
line between the two contacts. The distance will be displayed as
the Chord in the Contact Information window.
E.4.2 Contact Mensuration
When you have an image of your contact in Target, you can measure, or
mensurate
, it in three dimensions: width (across track), length (along track),
and height (also along track). A contact’s width is always measured across-
track (the abscissa vector); its length is measured along-track (the ordinate
vector). The implication of this rule is that an object’s narrowness or fatness
does not necessarily translate as width or length when you are mensurating
it. For example, if your contact is a ship lying across-track in your imagery,
the ship’s width is measured along the bow-to-stern direction. That same
ship’s length is measured from its fattest distance (usually amidships) in the
side-to-side direction: port to starboard or starboard to port, in this example.
If an object has any significant height, it casts a shadow. When a shadow is
present, Target can calculate an object’s height from its shadow. Look for
the shadow to the outside of the contact. The shadow is to the left of the
contact for a port channel and to the right of the contact for a starboard
channel. A negative range in the Cursor box of the Contact Information
window indicates a port-side image and a positive range indicates a
starboard-side image. A separation of the shadow from the contact indicates
that the contact is moored; in such a case Isis will calculate the moored
altitude based on this separation.
Appendix E: Using the Target Utility