Analysing the results of an
airborne test for oceanic Remote Sensing over Jiao Zhou bay
Chen Ken, Luo Yanyan, Liu
Zhishen Shandong College of Oceanology, Qingdao, China Introduction Shandong College of Oceanology organized an airborne test of remote sensing over Jiao-zhou Bay, nearby Qingdao, during the last week, Sept., 1979, and the airborne test was synchronously accompanied with the sea trial and ground measurements. In this test, we obtained a lot of data and information, and achieved our premediatated aims. This paper mainly discussed our analytic methods and analysed data and information given by our test. The aims of our test are:
On the basis of our possible conditions, this is a trial test, a test for principles and methods. II. Test Conditions and Sensor Our test aeroplane was a helicopter made in China. Our flight heights were from 500 to 2500 meters. Our flight speed was low, from 50 to 150 km/hr. In the test, airborne remote sensors were:
Using the above analysis methods, we have analyzed our gained data form the test, and obtained several results as in the following: A. Hydrologic information of the sea Whether the photos are of the visible waveband or of the thermal infrared waveband, the demarcation line between sea water and terrestial region is apparent. Furthermore, we can also recognize the hydrologic information of the sea: (1) the shoal water zone (2) the deeper water area (3) the muddy area (4) the zero-line (5) the temperature area (6) the surface wave, etc. Taken by the optical scanning radiometer of two wavebands, photo 1 and photo 2 were photographed synchronously. Photo 1 belongs to the visible waveband. The reflectivity of the land in the photo is intense, and thus the tone is light. The reflectivity of the water area is weak and thus the tone is dark. Photo 2 belongs to the thermal infrared waveband. In the photo, the dark tone represents the higher radiating temperature. The temperature of the land is higher than that of the water by day, but lower by night. Huang Island is in the middle of the photo, Jiao-nan county is in the west of the photo. There is the water area and the dam between Huang Island and Jiao-nan county. The width and the length of the water area are both about 2 or 3 kilometers. In this region, the tone is between the land and sea water. In the north and the south of this water area, there are two large shoal water areas and muddy area. As we compare photo 1 with photo2, the shapes of these images are analogous. As we compare these images with the oceanographicla charts, the shoal water areas and the muddy area in the photos correspond to the regional inside the zero line. In the muddy area, the people and ships can effective for the detective method in the offshore region. The visible light can pass through a certain depth in seawater. This property can be use to detect the shoal water area. The optical radiometer used in our test is not in separate spectra. Nevertheless the intensity of the reflective light of sea bottom is related to the sea depth and the transparency of the sea region. At Jia0 – zhou Bay,m the transparent depth is about 3-5 meters. By way of the gray scale of images, we can roughly recognize the shoal sea depth and the amount of water hearing of the muddy area. Using the photo of the thermal infrared band, we can recognize the surface temperature of the sea area. The land and the water. The land and the sunshine have effects on the surface temperature of the shoal water area. The gray scale of the photo is corresondent to the depth of the shoal water area. In the muddy area, the surface temperature is correspondent to the amount of water-bearing. In the deeper water area of Jiao of sea water, the surface temperature of all areas is nearly the same. In our test, the surface temperature which measured in situ was nearly 23-24° C. Due to the character of the instrument, measurements of temperature were of relative values. Each gray scale in the photo corresponds to the temperature may be obtained on the basis of gray scale of the photo. See photo 3, at that time, the helicopter flew at low altitude of 500 meters. From this photo, we may recognize the sea surface wave. Using this kind of photos, we can analyse the directional spectra and the period spectra of sea wave. On the basis of the flight height and magnitude of the photo, this area is about 100 meters long and wide. B. Pollution of the sea The environmental pollutions of the sea have a great damage to the health of the people and fishery resources. It must be noticed to prevent pollutions. Pollutions of the sea contain: heat pollution, sewage of industry outlet, oil detected in our test. The oil pollution of the sea is formed of oil spillages form ships at sea, and oil leaks form shipwreck. The oil pollution of the sea was detected in our test byusing visible and infrared wavebends. This is because the emissivity for petroleum products is weaker than for calm sea in the thormal infrared waveband and its reflectivity is higher than that of the calm sea surface. In the photo of IR waveband, due to the emissivity of oil slick equals 0.97, the emissivity of sea water equals 0.99, so the tone of oil slick in the photo is lighter than that of sea water. Comparing photos taken at different times near the ship-factory, we can verify that there were oil slicks on the sea surface. Photo 4 is of visible waveband. The altitude of the helicopter was 500 meters. We can apparently recognize the oil pollution of the sea surface. Using the altitude of the helicopter and the covered area of the photo, we can calculate the area of oil pollution. The area of the oil pollution is about 50-100m wide and more than 500m long. These data are coincident with the measurements in situ. Form photo 4, we can realize the source of oil diffusion and the direction of oil diffusion. The sewage of industry and the heat pollution flow into the sea form the land. It forms pollutions of the sea. The water colour of sewage is black grey and turbid, and thus the reflectivity is weak, the tone is dark in the photo of visible light. He emissivity of sewage is less, thus, the tone is bright in the IR photo. The temperature of heat pollutionis higher, thus, the tone is uak in the IR photo. The temperature of the heat source is higher, sometimes, 6-7° C higher. See photos 5 and 6. In photo 7, we can clearly recognize dense smoke out of the chimney of a factory. It forms air pollution. As remarked above, there are many kinds of pollutions at the se ports and industry regions, and it was verified that the remote sensing techniques are the useful method of detecting pollution. C. Coastal geomorphograph For the sake of requirements of harbour engineering, fish cultivation and beach exploitation, etc, geomorphographic data of the coastal regions should be provided. Thus aerial remote sensing has the following uses: 1) Drawing the demarcation line between sea and land. In the visible and infrared aerial photos, the sea, rivers, resourvoirs and pools possess the obvious presentation, their boundaries are distinct and clear. Not only the demarcation line between sea and land, but also the water system on ground can be drawn out, see our photos mentioned above. 2) Beashore and shoal water zone. As declared above, photos 1 and 2 show the new wharf of Huang Island, and the dam connected Huang Island to Jiao—nan country, and the muddy area, the shoal water zone by the two sides of Huang Island. 3) Lnad appearance. Despite of large image distortion, we could also recognize the river, bridges, highways, factories, beach, field and mountains etc. See photos 8 and 9. 4) Temperature distribution of the land. Infrared aerial photos recorded thermal characteristics of ground objects. For instance. Industrial regions have higher temperature, population regions have mediate temperature, the objects of high temperature are outstanding in the photo. However, the objects of ordinary temperature, for example, soil, rock, forest and roads can also be discriminative. See photo 10. D. Nightly thermal radiation image In the night, without the influence of solar radiation, ground shadows would disappear, the presentation of the thermal radiation of ground objects would be further clear. Different ground objects would have different ground objects would be further clear. Different their aerial photos would have larger differences in tone signature by night than by day. See photo 11. E. Microwave information 3 cm microwave scanning radiometer has digital records. Photos 12 and 13 represent microwave information. Each code contains its certain meaning. According to the law of Planck, the radiant energy of microwave of a ground object depends on the temperatures of the ground object tand tis specific radiance. Hence, different ground objcts have different apparent temperatures and different codes. The code of sea water is 1, codes of oil pollution are 2,3, 4, and codes of the land are 7,8,9, By photo 12, oil pollution and sea water can be resolvable distinctly. By photo 13, sea water and the land can be resolvable too. At the flight height of 1000m, by way of the major lobe angle of the microwave radiometer, we can derive out the area represented by a code, about 50 X 50 m2 . Composing the whole picture, we have obtained the profile of the land and the magnitude of the area of oil pollution. In the whole picture, the demarcation line between the land and sea water is corresondent with the map of Jiao-zhou Bay. This test verified that is microwave radiometer canbe used in coastal regions, and we obtained distinct digital pictures. Rectircted byu the proper characters of this radiometer, It is available for the use of large area, not available for other oceanoic information. |