Throughout this Section we have taken looks from space and the ground at modern cities, although some have old roots. As a finale, let's look at several striking examples of how remote sensing participates in archaeology, both in terms of ancient cities and of regions with no evidence of buildings but signs of human activity. We start with a look at one of the famed cliff cities in the U.S. Southwest, known as Chaco Canyon, in New Mexico. It was occupied by Pueblo and Hopi Indians between 850 and 1250 A.D., then largely abandoned (about the same time the the Anastasi Indians disappeared (experts think that a prolonged drought caused abandoment of many sites and migration to better climes). Here is a view from IKONOS and a ground photo of Pueblo Bonito:
Below is a more modern "relic" - the star-shaped Bourtange Fortress, in the Netherlands, about 42 km (26 miles) southwest of Groningen. Built in the 17th Century, it withstood a number of attacks during the Eighty Years war. It occupies a sandy ridge midst now heavily-farmed "moors" underlain by peat. After this star within a star redoubt fell into disrepair, it has been restored to almost its original state, as a major tourist atrraction. This IKONOS image shows it at 1 meter resolution, first in its setting within the town and then as an enlargement:
The most famed excavation in Europe is that of Pompeii, a small city near modern Naples, that along with its sister town of Herculaneum, was totally buried by an glowing ash avalanche released during the 79 A.D. eruption of Vesuvius. Here is its location as displayed by a yellow circle on a SIR-C radar image. Beneath is an aerial oblique photo of the present-day ruins.
The highlight of any visit to Pompeii is found in a room in which human body shapes were preserved as casts - made by backfilling the spaces in the ash that survived even as the bodies disappeared through decay. This is what you should see:
(Note to male readers: Be sure you see the room with the scatological graffiti.)
In modern Italy, Vesuvius is close to the large port city of Naples. As evident here in an aerial oblique photo, another Pompeii-like eruption could dangerously affect that city and the towns around it. So, Vesuvius' activity is closely monitored:
This next scene was taken by the IKONOS sensor. The resolution here is 4 meters. Before reading the caption or the next paragraph, take a wild guess as to its identity (clue: it is in modern Turkey not too far from Istanbul, and near the Hellespont - gateway to the Bosporus).
Next to Pompeii, this is probably the most famous rediscovery and excavation in modern times. The city is the fabled Troy written about by Homer. It was settled by the Aecheans of early Greek history and was laid siege around 1200 BCE by the Greeks; it is where the Spartan warrior Achilles defeated the Trojan Prince Hector (who in turn was slain by Paris, the lover of the reknown Helen) and where the myth(?) of the Trojan Horse led to the downfall of King Priam as Troy was overrun when soldiers inside the huge horse debarked and opened the gates to allow the Greek hordes to enter the walled city. Ultimately, it was rebuilt and buried several times, disappearing from sight so that its very existence was questioned. But, the German archaeologist Heinrich Schliemann firmly believed it was real and out there somewhere. Beginning his digging in 1870, he eventually proved to the world that this lost city was an historical fact (but the actual site to the north, near the entry to the Bosporus was unearthed later).
At least 9 levels of urban construction at the Troy site were found during the diggings. These represent hundreds of years of time, going back perhaps to 2500 B.C. A schematic showing reconstruction of Troy at different times appears below, followed by a map that highlights Troy VI, the purported time of the Trojan War.
Remote sensing has had several notable successes in finding evidence of buried cities. One is the lost "Arabian Nights" city of Ubar, which was an important trading center in the eastern Arabian Peninsula (in today's Oman) for several thousand years until it disappeared perhaps around 300 A.D. Using remote sensing, Dr. R. Blom and others found evidence in this Landsat image of ancient trails that led to a spot on the side of a mountain.
SIR-C radar (see page 8-7), operated from the Space Shuttle, also could pick out these caravan roads (in pinkish-red) that seemed to converge near a dry stream or wadi.
When these archaeologists visited the site area singled out in the imagery, and carried out a "dig", they found evidence (including remnants of walls at the surface) of a large fortress that guarded this city, which apparently was destroyed by invaders after capture.
Eygpt is a land noted for its ancient sites connected with the reigns of numerous Pharoahs who built great temples and pyramids during their dynastys. Satellite imagery is being used effectively to look beneath desert sands to locate buried ruins. The Great Temple of Aten, located on the east bank of the Nile about 300 km (200 miles) south of Cairo close to the modern town of Amarna, was known since 1935. Prof. Sarah Parcak of the University of Alabama-Birmingham uses Quickbird and other satellites to search for signs of hidden antiquities. She has found much more of the Aten temple, which has now been excavated. Here is a vertical view from space and a perspective view that shows the temple layout:
Satellite imagery is being used in an exotic hunt for a biblical treasure: Noah's Ark. Claims of it being in glacial ice on Mount Ararat in Turkey (location chosen from bibilical interpretation) has been reported for six decades now. This illustration documents the first attempt in 1948 to pinpoint something (initially just called "the anomaly" on the mountain that could be a ship:
Mount Ararat itself is an imposing volcanic stratocone, whose appearance from the ground is captured in this SRTM-Landsat color composite:
The anomaly is buried in ice. Various satellites have taken additional images. Here are two
Something unusual is there. The site has been visited several times on foot, with (wild??) claims of discovery, but nothing really convincing. The reader is invited to surf the Internet under the headings of "Mt. Ararat" and "Noah's Ark", but be prepared for fanciful speculation.
One of the great ruins in the Middle East is Persepolis, in modern Iran. For nearly two centuries, starting in 515 BCE, it was the capital of the Achaemerid (Persian) Empire. Names associated with it are the Persian emperors Darius and Xerxes and its conqueror Alexander the Great. Below it is imaged by the ALI on EO-1, then from an aerial photo, a ground scene, and a plan map of its layout in its heyday:
Remote sensing has had a number of other successes in helping archaeologists to search for new ancient sites or extend their knowledge of ones being worked on. On page 15-10 this subject is reviewed in depth, using an example of Celtic-Roman-Medieval ruins in Burgundy, France, analyzed both by SPOT and radar and by the Geographic Information System (GIS) methodology.
In South America, one of the most famous - and mysterious - sites of some, still not adequately explained, ancient activity is the Nasca (or Nazca) lines in the dry low hills and plains in Peru. This Terra ASTER image shows these features - remarkably straight lines as much as 10 km long, some of which cross. Imaginative interpreters postulate these to be landing strips for extraterrestrial vehicles (space ships). Other opinions ascribe them to some still mysterious project conducted by pre-Columbian South American natives. Below the ASTER view is a higher resolution IKONOS image:
Elsewhere in Peru is perhaps the most famed of pre-Columbian archeological sites in South America. This is the ruins of the Inca city, Machu Picctu, built in the 15th Century and abandoned a century later. Situated in the Andes, on a small flat plain near two "sugarloaf" mountains, at an elevation exceeding 2800 meters (9250 ft), multitudes of tourists journey by rail from Lima nearly 400 km to the west-northwest, to witness this fascinating site set against a beautiful background of rugged mountains (a small town nearby at the railhead houses some of these visitors). Quickbird has imaged Machu Picctu at 1 meter resolution, shown below, with an aerial view beneath that gives an overview of the surviving ruins.
In Asia, Cambodia and neighboring modern states were once home to the Khmer civilization which flourished between 800 and 1400 AD. These were Hindu-Buddhist worshipers who developed a distinctive art and were skilled engineers. By 1100 A.D. a complex urban center called Angkor Thom, with up to a million people, had developed in west central Cambodia. As seen from space in this ASTER image, a large manmade lake (the Western Barat Reservoir), a water supply, a walled city (larger square), and a temple (smaller square with moat) appear in this area north of a natural lake, Tonje San.
Much detail of the various building in Angkor Thom is shown in the SIR-C color composite
Until the 20th century, this region was heavily forested so that the Angkor ruins were poorly explosed. Much of the land has now been cleared. This map shows the spread of central buildings area:
By far the centerpiece of this complex is the famed Angkor Wat temple, which has been freed from jungle vegetation and restored. It is now the main tourist attraction in Cambodia, reached by road from Phnom Peng, the capital. Here are two views:
Built around 1140 A.D. by King Suryavarman II, the interior has been studied leading to this functional map:
A Landsat-7 subscene shows some of the details of the area, including roads and a modern air strip.
Prior to clearing the temple grounds, an early radar image showed the extent of trees and the ability to penetrate the vegetation to see parts of the Angkor Wat group.
NASA JPL flew a radar mission of Angkor, leading to this perspective image:
In Section 6, on page 6-14a showing Beijing, China, the famed Great Wall built nearly 2000 years ago is visible. But it really stands out in the SIR-C images shown here:
The Wall, constructed for defense against the Mongols and others, is 6700 km (4160 miles) in total length. Large parts of it are located in mountaineous terrain:
Now, let's leave these once gloried ruins to journey again into the vast countryside, this time back to the U.S. by considering in Section 5 locations in southwest Utah and the Plains of Oklahoma, as examples of how remote sensing contributes to mineral and oil/gas exploration.