Satellites track icebergs

In May this year the National Ice Center in the US reported the sighting of a new iceberg, C-19 which broke off from the Ross Ice Shelf down in the Southern ocean.

C-19 is a large sheet of glacial ice which extends from the Antarctic mainland into the southern Ross Sea. The imagery used by the NIC in ice identification is satellite derived. In the case of C-19, the iceberg was spotted by the Center using the latest satellite image from the Defense Meteorological Satellite Program's Operational Line Scan Infra-red sensor.

The majority of this imagery is in the visible or infra-red band of the electromagnetic spectrum, says Chris O'Connors, acting public affairs officer at NIC.

O'Connors says the National Ice Center imagery is manually interpreted. New icebergs are identified based on the scientist's knowledge of the ice shelf and the physical characteristics of the glacial ice as seen on the satellite imagery.

When the data is received at NIC it would have been preprocessed at one of many data collection ground stations located around the world. Large mainframe central computers process signal data received from various satellites into polar stereographic and mercator projections.

"When data is received at NIC geo-coding and in some cases geo-referencing processing is required," he said. This processing is done in batch mode using smaller computers such as Sun Solaris servers, PC's running Windows NT or Linux. Imagery analysis software is then used to aid the analysts in deciphering the image.

The actual image observations are made on the NIC's analyst system developed by Lockheed Martin called CARTERRA. CARTERRA is a Windows 2000 platform with dual monitors and dual 1GHz processors. CARTERRA integrates several commercial off the shelf software (COTS) to create an analysis. COTS software included in CARTERRA are ERSI's ArcInfo, ArcView, ERDAS Imagine, and Sensor System's Remoteview.

All of the COTS software is then imbedded in a rapper created by Lockheed Martin to be a completely integrated system. To be integrated can mean different things. "The way we look at it is to be able to search for data, send the data directly to an image viewer, create an analysis using the image tools of that viewer, insert attributes on the satellite image and to combine the analysis and attributes into a geo-spatial end product," said O'Connors.

Sounds simple enough.

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