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The Queen Charlotte Islands are known by the native inhabitants as "Haida Gwaii", which means "Islands of the People". The archipelago consists of about 150 islands, the two largest being Graham Island to the north, and Moresby Island to the south. The latter island contains Gwaii Haanas National Park Reserve/Haida Heritage Site. This overview image shows a portion of both Graham and Moresby Islands divided by Skidgate Inlet, the northernmost inlet visible in the image. This Landsat TM image is being displayed using bands 3, 2, and 1 as red, green, and blue. This combination is referred to as a "natural colour" simulation because each band used is being displayed as its true colour - almost exactly the way you'd see it with your own eyes. Among about a dozen major communities on the Queen Charlotte Islands are Queen Charlotte City and Sandspit, both located on the shores of Skidegate Inlet. There are many forest clear cuts visible on the islands as well as other clues to human presence. Also seen here is the spectacular mountainous terrain spanning the entire western side of the Queen Charlottes.

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Question: Why are the inland water bodies (both fresh and salt water) generally darker than the open ocean?

[ Answer ]
 

About this Image

Location: Queen Charlotte Islands, British Columbia NTS map(s): 103 F/G/C Location Map: See a detailed map (1:1M) of the region Image Date: October 1995 Satellites/Sensors: Landsat Thematic Mapper (TM), Bands 1 to 5 Resolution: 86 m pixels Image Area: 65 x 61 km Image Features: Mountains, Queen Charlotte City, clear cuts, forest, Sandspit, airport, sand, shoreline, islands Related Tour Images: Port Renfrew, British Columbia Related Glossary Terms: These terms from the CCRS Glossary may help you to understand this image and its interpretation: additive colour, change detection, colour composite, image enhancement, image texture, tone, brightness, contrast Related Tutorial Sections: These sections of the "Fundamentals of Remote Sensing" tutorial by CCRS will help you to better understand this image and its interpretation: 2.3   2.8   4.2 Image Credits: Landsat image received and analyzed by the Canada Centre for Remote Sensing; Pre-processed by and provided courtesy of RADARSAT International Inc. Airphoto and background information courtesy of the British Columbia Ministry of Forests

 

Question:

Why are the inland water bodies (both fresh and salt water) generally darker than the open ocean?

Answer:

The main reason for the difference in tone has to do with wind conditions. The inland lakes and ocean fjords and bays are effectively sheltered by the surrounding mountains and thus have a calmer, smoother water surface. The smooth surface results in 'specular' reflection of the sunlight, resulting in less solar radiation being reflected back to the sensor, producing a darker image tone. In the open ocean the stronger winds produce a rougher water surface, which is more effective in reflecting sunlight back to the sensor (diffuse reflection), producing a brighter image tone.