The issue of high spatial resolution

Major Applications of Satellite Monitoring of the Arctic:

• climate and environmental change

• surveillance of sea ice regions and iceberg occurrences for safety of marine operations

They require wide regional coverage of satellite images which typically have low spatial resolution between several tens of meters and kilometers.

• Difficult to identify targets such as narrow open water leads, small icebergs, sea ice ridges

To obtain information at a level of detail of a few meters is possible in accessible areas with dense networks of measurements stations and points of observation.

In remote regions, however, this type of information has to be made available from satellite images which cover smaller areas with high spatial resolution.

Examples of applications requiring high resolution imagery over local areas:

• tactical navigation of cargo and cruise ships and fishing vessels operating close to the sea ice edge, in sea ice, or in waters with iceberg occurrences;

• on-ice traffic e.g. in fjords of Greenland and Svalbard, or on landfast ice in the Baltic Sea;

• provision of information needed in local high-resolution forecasts of ice conditions;

• complementing in-situ data acquisitions at research stations or of ship and airplane expeditions.

Advantages and challenges of multiple sensor image analysis

Different satellite sensors acquire images over the Arctic:

• multi-spectral imagers (e.g. Sentinel-2)

• thermal infrared sensors (e.g. Landsat 8 and 9)

• synthetic aperture radar (SAR, e.g. Sentinel-1)

They have strengths and limitations.

• Optical images from multi-spectral imagers correspond to human vision but are restricted to times of daylight and cloud-free conditions.

• Thermal infrared sensors reveal differences of ice and water surface temperatures also in darkness but cannot see through clouds.

• Radar is independent of daylight and in a certain frequency range of cloud cover, but images need to be interpreted considering different factors such as frequency, polarization, and incidence angle of the radar waves.

Used as stand-alone, the images are prone to misinterpretation. Hence, the combined analysis of different image types (optical, thermal, radar at different frequencies and polarizations) provides higher confidence in the retrieval of information about sea ice conditions and presence of icebergs. But challenges remain, such as insufficient spatial overlap and time gaps between the acquisitions of single images, different levels of detail, and requirements for operational use.

To address the need for locally detailed information and for higher confidence in image interpretation through multiple sensor image analysis our team proposed the project

                                                            HIRLOMAP

as part of ESA’s Sentinel Users Preparation (SUP) initiative: [SUP-1] - Applications Preparedness with stakeholder and end-user participation.