SPRINT-Nav Mini performance descriptions explained

SPRINT-Nav Mini describes performance in two ways: typical survey and distance from origin. All positioning error is quoted to CEP50 without USBL or GPS.

Typical survey

Typical survey describes how the SPRINT-Nav should perform when doing a “typical survey” mission. This would be best described as a “lawnmower” or “grid” survey, as would be typical in a Side Scan Sonar or Multibeam Echo Sounder data collection mission. This would involve:

• Approximately 1 km in one direction
• 180-degree turn
• Approximately 1 km in another direction
• 180-degree turn
• and then repeating the above

Distance from origin

Distance from origin describes how the SPRINT-Nav should perform when travelling from one point to another in a straight line. Typically used for an AUV or Vessel when leaving port and travelling to a location.

Typical survey values are always lower (higher performance) because many of the common bias (not error) which are associated with Hybrid-Navigation systems (SPRINT-Nav/SPRINT-Nav mini) tend to cancel out when a vehicle travels on an opposite heading over a similar area of seabed. Examples of these bias that could cancel out are described below:

Sound velocity bias

If a sound velocity sensor is reading incorrectly say for example 1% wrong, the bias will apply as a scale factor which will cause the distance measured by the DVL to be either shorter or longer than the true distance. When the vehicle turns the bias will measure the same wrong distance, causing the error to cancel out.

Heading bias

If the heading is reading higher or lower than truth two things may happen:

1. On a reciprocal line the bias may cancel out, i.e. one side of truth in one direction, the other side in the other direction.
2. On a reciprocal line the bias or error in the heading value may be lessened because the system has rotated and thus has more observability, causing it to settle nearer to truth.

DVL aided

When the DVL is tracking the seabed successfully, in the web UI this would display an “OK” message on the main page.

Guidance and Navigator

Guidance is a variant of SPRINT-Nav mini which does not function as a full INS, meaning it does not calculate position. These are typically used on simple ROVs.

Navigator is the main and biggest selling variant of SPRINT-Nav mini which calculated and provides a full INS position. This is the variant for which the 0.05/0.3% error values are stated.

Contact Support@sonardyne.com for more information.