April 25 2024

SAR Image of Castle Bay, Alaska acquired in October of 1997

Synthetic Aperture Radar (SAR) is an active remote sensing technology which uses microwave electromagnetic energy to form complex images of terrain reflectivity. Because SAR is largely unaffected by the presence of dense cloud cover, it delivers flexibility over weather constraints, and introduces the possibility of nighttime operations. Over the past few years, high resolution airborne and satellite SAR systems have become available for civilian use. Some systems have resolutions and accuracies that approach those realized photogrammetrically. The scene above shows a 5 nautical mile stretch of the north coast of Castle Bay, AK, acquired through dense clouds. The image was generated by engineers at NGS from raw phase history data acquired aboard the Environmental Research Institute of Michigan (ERIM) DCS aircraft, and using image formation code written at Sandia National Labs (SNL). Below, the left photo shows the view out the starboard window of the ERIM aircraft at the time the SAR image was acquired. The right photo shows NOAA and ERIM engineers in the DCS aircraft, on station over Castle Bay.

 

View from ERIM aircraft over Castle Bay, AK

NOAA and ERIM engineers aboard ERIM aircraft


In a second experiment with airborne SAR, NGS has contracted with a private vendor,  INTERMAP Technologies Ltd., to obtain STAR-3i imagery of Yakutat, AK. Shoreline data mapped from this system will be compared to shoreline measured photogrammetrically. This image at right is an example of coastal imagery acquired with the star 3i system over Bay St. Louis, Mississippi (Image published courtesy of INTERMAP Technologies Ltd).

Aside from our experiments with airborne SAR, NGS is also experimenting with satellite based SAR. We have obtained a fine resolution (8-meter) RADARSAT scene of the Castle Bay technology validation site. We are evaluating the accuracy of shoreline data mapped from the RADARSAT image, by comparing the shoreline vector to a more accurate representation of the shoreline measured from aerial photographs.
STAR-3i Image of Bay St. Louis, MS
Star-3i Image

See more information on the Castle Bay, Alaska project.