Mouths of the Irrawaddy River, Myanmar (Burma) – December 11th, 2008
This beautiful, sharp image of the mouths of the Irrawaddy (Ayeyarwady) River in Myanmar was obtained by overlaying a black and white ASAR (radar) image and a colored MERIS one.
Creating such a composite image allows viewers to observe details in one picture that could previously only be seen by comparing two different images side-by-side.
We call this technique SAR-Sharpening as it is derived from a similar method named PAN-Sharpening, only based on image data, while the SAR-Sharpening is generated by combining a high resolution Radar image with a medium resolution optical picture.
For example, the winding paths of the rivers are seen clearly in the composite color image thanks to the overlay.
However, upon examing the images separately, the rivers in the ASAR image appear quite sharp, whereas in the MERIS image their path is rather blurred (also due to the different resolution: 30 meters for ASAR and 300 meters for MERIS).
In the composite image it is also possible to observe sediments flowing into the Indian Ocean at the same time as the ocean currents (the latter usually only visible by radar). These currents can be identified as the darker area in the lower right corner visible upon opening the full image.
However, when the images are separated, in the ASAR one the currents are visible, but the sediments cannot be seen. In the MERIS image the opposite is true: the sediments are easily spotted but the currents are invisible.