●Underwater short baseline? It is the underwater monitoring and command system. The short baseline sonar system is used in underwater archaeological practice. This is the first time in China that the Xiaobaijiao No. 1 shipwreck has been used in archaeology. In fact, this sonar system can also be said to be a measurement and tracking system. Geophysical exploration equipment in water is basically acoustic signals. Two dumbbell-like things are suspended under the water on both sides of the cabin to display the activities of the underwater archaeological team and can display the scope and status of the personnel's activities in real time.
●This board with a shallow stratum profile shaped like a shark is hung under the water next to the cabin. The ship drags it along to detect relics buried below the surface of the seabed and transfer the data to a laptop computer. , based on the echo signal strength, the changes in the geological structure below the seabed surface are analyzed to determine whether there are ruins of sunken ships under the mud.
●The only difference between underwater cameras and land cameras is that they are super waterproof. Different from ordinary cameras, underwater cameras are covered with a waterproof shell. The recorded short videos can be used as archaeological records. Information and file preservation. ?
●Ocean Magnetometer? The yellow and white instrument is suspended under the hull. It detects underwater metal objects based on the principles of the earth's magnetic field. The working principle is a bit like detecting landmines on land.
●Differential positioning system? Plays the role of GPS, that is, DGPS, with high accuracy. There is no reference object at sea, and it is difficult to distinguish the exact destination with the naked eye, so the instrument needs to be positioned accurately at sea and on land, with an error within one meter.
●Underwater loudspeaker? What instructions do people on the surface give to underwater divers? They can convey the commands through underwater loudspeakers.
●Oxygen content tester? This time the underwater archaeological team used a high-oxygen diving method. The oxygen concentration is higher than the proportion in normal compressed air. The advantage of this is that it can appropriately extend the underwater archaeological team’s time. underwater residence time.
●Underwater wireless communication system? A method of communication under water, which can realize three-way communication between underwater and above water, and between underwater and water surface without the help of cables.
●Underwater video surveillance? It allows people on board to monitor the work of underwater archaeologists in real time.
●The British L-3 System 3900 high-definition side-scan sonar system emits sound to the seafloor, and judges the sound waves reflected back from the seafloor to detect the changes in the surface topography of the underwater seabed. The purpose of detecting relics.
Experts talk about the process of underwater archeology
Fu Yimin is an associate researcher at the Municipal Cultural Relics Protection and Management Institute (Institute of Archeology) and a trainee in the second phase of the China Underwater Archeology Professional Training. In 1999, he participated in Fujian Underwater archaeological practice at the Baijiao shipwreck site in Dinghai, Lianjiang County, Lianjiang Province. "The Dinghai Baijiao shipwreck carried Fujian black-glazed porcelain, which is different from the Xiaobaijiao No. 1 shipwreck that produced a large amount of blue and white porcelain." Yesterday, Fu Yimin introduced the working procedures of underwater archeology and the equipment needed in Ningbo.
The first task is to find and locate underwater ruins
Fu Yimin said that the principles of underwater archeology are the same as those of terrestrial archeology, but the working environment is different and a large number of modern scientific and technological methods and means are required.
“Shipwrecks have an obvious characteristic. The ruins they form are generally one-off, and there is no distinction between early and late archaeological strata. The hull, cargo and living utensils on the ship reflect the side of society at that time. , which can determine the age and nature of shipping.”
Finding and locating underwater ruins is the first step. "It can be searched through diving and instruments. Diving is used to search for common floating lines. Long ropes are put on the bottom of the water and tied to buoys in sections. The divers find the target and mark the nearest place to the buoy. There is also circle searching, and the location of the underwater ruins is determined after land surveys. At the approximate location, a fixed pile is dug on the bottom of the water and a rope is tied. The diver tightens the other end of the rope and searches the seabed in a circle around the fixed pile. After returning to the original place, the rope is retracted and the search continues in circles," Fu Yimin told reporters. "The radius of the circle is generally about 10 meters, because there are undercurrents, tidal surges, etc. at the bottom of the water. The visibility under the East China Sea is about 5 meters. It is basically unclear and you can only rely on touch.
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Instrument search means searching with the help of modern equipment, including scanning sonar systems, shallow bottom profilers, magnetometers, etc. Fu Yimin said: "Modern equipment combined with divers' underwater search is a better method. "
After finding the underwater ruins, it is necessary to locate them accurately. "Positioning is to mark the specific location of the ruins on the sea map and indicate it with the longitude and latitude, so that the ruins can be found quickly at the specific location. There are two main positioning methods: one is positioning using shore reference objects and accompanied by scenery photos; the other is instrument positioning, that is, using GPS for accurate positioning. "
The preliminary investigation work of underwater archeology is very important. "The Xiaobaijiao No. 1 shipwreck has undergone a large number of shore surveys. Through the information provided by fishermen, the underwater archaeological team determined the scope, nature, value and The underwater environment of the sea area, etc., to understand the preservation status of the Xiaobaijiao No. 1 sunken ship, the items on the ship and the degree of burial, the sand content of the seabed, stratigraphic accumulation, etc., and conduct underwater photography, small-scale excavations, etc. The preliminary work is complex. ”
“The Meiyuan Stone is the heaviest, so it came out of the water last.”
For the sake of safety and mutual cooperation, underwater archaeological operations require two people to enter the water at the same time. “One person excavates, and the other Record and measure. "Fu Yimin introduced the underwater operation method, "Generally, a 2 meter × 2 meter square survey is used. Hard exploration means that a metal frame is placed on the site. A frame is a exploration, which can be used for a long time. The other is soft exploration. "He told reporters that hard exploration is currently generally used because it is more accurate.
Accurate recording, measurement, drawing, and photography are the differences between underwater archeology and general salvage. How do divers communicate underwater? “In the past, when I participated in underwater archeology, I could only use specific gestures, such as clenching my hands and pointing my thumb upward to indicate water. Now, with the underwater wireless communication system, we can realize three-way communication between the surface and underwater, and between underwater and underwater. . "There is also an underwater video surveillance system to control the underwater excavation situation in real time. In addition, underwater photography is also an important recording method, and the excavation objects and the excavation process must be recorded in detail.
In Talking about the issue of the sunken treasure being released from the water, Fu Yimin said: "The extraction of items follows the principle of 'first up, then down, first easy, then difficult, and handle with care'. The Meiyuan Stone is the heaviest, so it was extracted from the Xiaobaijiao No. 1 shipwreck and placed at the back. "Items are packed into mesh bags or frames in batches and brought out of the water. After preliminary washing, they are registered, numbered, and collected.
The most fearful thing about underwater operations is entanglement
Fu Yimin introduced personal diving equipment , underwater cameras, underwater wireless communication systems, underwater video surveillance and other major equipment. "The underwater situation is complex, especially in the pitch black of the East China Sea. As an underwater archaeological team member, you must have a good psychological quality. When you are entangled in aquatic plants, fishing nets, etc. Don't panic, contact your companions in time and cut it off with a diving knife. "
The air supply equipment for underwater operations includes gas bottles and surface pipes. "Compared with gas bottles, the water supply air has a higher humidity and feels much more comfortable. He said that the disadvantage of tube supply is that the operator's range of activities is not large, and "it is suitable for underwater fixed-point work, such as underwater archaeological excavation and small-scale exploration and surveying." "In general work, two types of gas supply equipment must be prepared.
The excavation equipment is mainly a sand pump, "to remove the sand covering the ruins and relics, which is convenient for observation and recording, and is suitable for The underwater ruins have a sandy or muddy bottom. "
Fu Yimin also introduced work boats and working platforms. "According to different sea conditions and different conditions, different forms of work boats are used. The work boat can be a warship, a transport ship, a fishing boat, etc. It is used to place instruments, equipment, diving equipment, etc. It can also be used as a work and activity venue for participants, and it also provides convenience for divers to enter and exit the water. ”