Source: Satellite Radar

What is Satellite Radar data?

Skylight uses Satellite Radar as short form for Synthetic Aperture Radar or “SAR” or “Sat-SAR”. Satellite Radar is one method of imaging the earth from space. Similar to shore- and ship-based radar, satellite-based radar uses the reflection of radar waves to image the earth. Instead of the radar being emitted from a ship, it is emitted by a moving satellite. As a result, the images we receive of vessels are from above.

Open

Ship-based Radar

Open

Shore-based/Coastal Radar

There are several major providers of satellite radar data, the European Space Agency (ESA) for Sentinel-1, MDA for RADARSAT-2, and KSAT to name a few. Different providers offer collecting satellite radar with different frequencies, coverages, resolutions, and add-on services.

Across any source of satellite radar data:

• The images come in black and white

• Radar bounces off some materials (like metal) better than other materials (like wood), so some vessels are easier to see than others 

• Whether it is day or night does not impact the ability to detect vessels

• The presence of clouds does not impact the ability to detect vessels

What is resolution and why does it matter?

Resolution describes how detailed the image is. The higher the resolution, the better the detail, making it more likely to see vessel features and obtain better size and heading estimates. The lower the resolution, the more blurry the image. There is a tradeoff between resolution and footprint size. While higher resolution images are preferred over lower resolution images, the satellite must image a smaller area in order to capture higher resolution images. 

How does Skylight use this data?

Skylight uses Satellite Radar data to display vessels that are ‘dark’ (not carrying AIS) to users. Regular Satellite Radar vessel detections are available in Skylight from Sentinel-1. The table below provides additional details.