Posted on 04/24/2002 8:36:45 AM PDT by cogitator
The Bosporus is a strait that connects the Black Sea with the Sea of Marmara in the center of this view of northwest Turkey, taken during the Shuttle Radar Topography Mission (SRTM). The water of the Black Sea at the top of the image and Sea of Marmara below the center are colored blue in this image, along with several large lakes. The largest lake, to the lower right of the Sea of Marmara, is Iznik Lake. The Bosporus (Turkish Bogazici) Strait is considered to be the boundary between Europe and Asia, and the large city of Istanbul, Turkey is located on both sides of the southern end of the strait, visible as a brighter (light green to white) area on the image due to its stronger reflection of radar. Istanbul is the modern name for a city with a long history, previously called Constantinople and Byzantium. It was rebuilt as the capital of the Roman Empire in 330 A.D. by Constantine on the site of an earlier Greek city, and it was later the capital of the Byzantine and Ottoman empires until 1922.
The Gulf of Izmit is the narrow gulf extending to the east (right) from the Sea of Marmara. The city of Izmit at the end of the gulf was heavily damaged by a large magnitude 7.4 earthquake on August 17, 1999, often called the Izmit earthquake (also known as the Kocaeli, Turkey, earthquake), that killed at least 17,000 people. A previous earthquake under the Gulf of Izmit in 1754 killed at least 2,000 people. The Izmit earthquake ruptured a long section of the North Anatolian Fault system from off the right side of this image continuing under the Gulf of Izmit. Another strand of the North Anatolian Fault system is visible as a sharp linear feature in the topography south of Iznik Lake. Bathymetric surveys show that the North Anatolian Fault system extends beneath and has formed the Sea of Marmara, in addition to the Gulf of Izmit and Iznik Lake. Scientists are studying the North Anatolian Fault system to determine the risk of a large earthquake on the faults close to Istanbul that could kill many more than the 1999 event.
Three visualization methods were combined to produce this image: shading and color coding of topographic height and radar image intensity. The shade image was derived by computing topographic slope in the northwest-southeast direction. Northwest-facing slopes appear dark and southeast-facing slopes appear bright. Color coding is directly related to topographic height, with green at the lower elevations, rising through yellow and brown to white at the highest elevations. The shade image was combined with the radar intensity image to add detail, especially in the flat areas.
Bosporus Strait and Istanbul, Turkey for the original page and a link to the big (5 MB) version of this image.
I've heard rumors that these radar images penetrate water. And that's their primary usefullness. Shows submarines in the water (ever wonder why we decommissioned SOSUS?). Shows wrecks on the bottom (ever wonder how its been so easy for some people to find specific wrecks lost for decades in the open ocean - hint - sonar hasn't improved that much).
Sure would like to see the original image.
I don't know much about the SRTM, but since the water looks very flat, they may not have done anything with radar returns over water and simply analyzed the land data. (The Canadian RADARSAT gets the best radar data over the ocean for waves and ice.)
It was a non-classified mission, and the first images came out showing the ocean bottoms, and these long cigar shaped thingies floating between the surface and bottom.
Surprise, surprise, surprise.
The first images were relased, but someone quickly realized the national security component, and classified it quick.
Nifty pics cogitator - I always look forward to them.
The data is collected by scanning the earth's surface to produce a "grid" of values that are then converted to the image you see by combining information (e.g. slope, aspect, elevation) to produce an idealized view of the surface.
Because the large water bodies have "zero" elevation and are essentially "flat" they are assigned a consistent color. Thus they appear unrealistic because there is no natural variation in shade. Because I have some experience in this, it is obvious that the whole thing is "unrealistic", but it is a beautiful image nonetheless.
The global digital elevation dataset that came from this program is a gold mine for those in geospatial data analysis fields.
The description (especially the last paragraph) is quite accurate.
Russ
LIDAR systems (that use active laser ranging) get about 3-meters of penetration in non-turbid water and has proved useful for characterizing the underwater surfaces nearshore.
Russ
I will, but I'll also tell you that the "Earth Observatory" Web site has a new image every day and feature articles about Earth science and remote sensing. Here's the link:
http://earthobservatory.nasa.gov/
I don't always use their images; I look at some current volcano and weather sites too (and this "Geology Picture of the Week" is just for fun anyway), but they have a good variety and frequently spectacular shots.
Good picture ...
That must have been some river.
Hey, sorry I'm late to reply to this: I was really busy for the past few days. Anyway, it's better than speculation; geological data pretty much confirms that this happened. It was some river; the stories I've seen indicate that the Black Sea would have been rising about a foot a day.
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