SARDOT denotes a predesignated geographical reference point relative to which isolated personnel report their position to recovery forces. In US military terminology it is called a Search and Rescue Point; the wording Search and Rescue DOT is also used. The shared point enables a relative location report using direction and distance.
A shared point for reporting position
The isolated person determines their position relative to the designated SARDOT and transmits the agreed direction and distance information. Receiving forces relate these values to the same point and derive the reported position.
Both sides need to know that reference in advance. Anyone who knows the point and the reporting convention can also interpret the same information geographically, so protecting the distribution of the reference forms part of preparation.
The point, direction and units must match
In the US Army PR system, the Personnel Recovery Coordination Cell distributes SARDOT information through PR coordinating messages. This includes the reference point's location, coordinate format and geodetic datum, and the formats for direction and distance. Sender and recipient use the same point, the same directional reference and the same distance unit.
A direction report also depends on which end of the line it starts from. Confusing the direction from the person to the reference point with the reverse direction places the reconstructed position on the wrong side. Interpreting a different distance unit changes the separation. Using a different SARDOT shifts the entire position reference even when the transmitted numbers have been received correctly.
Geographical reference and numerical encoding
SARNEG serves a different purpose: it replaces digits with letters assigned in advance. SARDOT provides the geographical reference for a location report.
The contact's position and identity
The position report helps recovery forces establish the person's location. They also check whether the contact is the person they are seeking. Authentication information and procedures are prepared for that purpose, including information in an ISOPREP.