An upward looking sonar (ULS) is a sonar

Sonar

Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...

 device pointed upwards looking towards the surface of the sea. It is used for similar purposes as downward looking sonar, but has some unique applications such as measuring sea ice

Sea ice

Sea ice is largely formed from seawater that freezes. Because the oceans consist of saltwater, this occurs below the freezing point of pure water, at about -1.8 °C ....

 depth and concentration http://mustelid.blogspot.com/2005/05/sea-ice-what-i-do-in-my-spare-time.html or measuring air entrainment from bubble plumes during rough seas.

Often it is moored on the bottom of the ocean or floats on a taut line mooring at a constant depth of perhaps 100 m. They may also be used by submarine

Submarine

A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

s, AUV

Autonomous Underwater Vehicle

An autonomous underwater vehicle is a robot which travels underwater without requiring input from an operator. AUVs constitute part of a larger group of undersea systems known as unmanned underwater vehicles, a classification that includes non-autonomous remotely operated underwater vehicles...

s, and floats such as the Argo

Argo (oceanography)

Argo is an observation system for the Earth's oceans that provides real-time data for use in climate, weather, oceanographic and fisheries research. Argo consists of a large collection of small, drifting oceanic robotic probes deployed worldwide. The probes float as deep as 2 km. Once every...

float.

External links

• http://aslenv.com/IPS.html
• http://nsidc.org/data/g01360.html