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Poster Session Q
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The application of airborne thermal infrared Remote Sensing to the detection
petroleum pipes
The selection of imaging condition
The selection of thermal infrared scanning image condition is the key to decide the infrared detection effects. The principle of imaging condition selection is that the detected objects produce maximum temperature difference against background, in addition to the weather condition at that time and the possible interference factors on the ground.
Imaging season: Considering the purpose of this test and the test area characteristics, we selected the middle ten days of December as imaging season. The meteorological data show that is early the middle ten days of December as imaging season. The meteorological data show that is early winter. The weather is gradually becoming cold, and the ground temperature decreasing. The surface soil was not frozen. The thermal conduction caused by underground pipes easily formed temperature anomalies on the ground, and often appeared as great difference of temperature. For the ground surface condition, the rice field was drawn off water, and the crops had been cutted off. The water level on the marshland decreased, and the reed became withered and yellow. SO, the interference factors from surface water and vegetation were almost eliminated or at the minimum level. It was very favourable for imaging.
Imaging time: Imaging at night is the presuposition for the thermal target detection with the surface as background, because the ground temperature-increasing phenomenon caused by sun radiation was removed. The ground test data showed that at the high latitude area, the ground surface temperature tends to be stable at 20o,clock at night to 6 o,clock next morning at this season. The temperature difference between different objects was clear, and the maximum difference of temperature appeared before the dawn. Considering the thick fog caused by the cold air before dawn at this season, and avoid the interference of the strong fog sbsorptivity we selected the period from 20 to 23 o,clock for flight imaging and got good results.
Flight altitude: The flight altitude not only decides the imaging scale, but also directly influence the object resolution of scanning image.
The mathematical expression of the object resolution[2]:
d = b.H -------------------(2)
d: Object resolution(m)
b: The transient view angle for scanning(2.5m rad)
H: imaging flight relative altitude(m)
It is shown in the expression (2) that the object resolution is inversely proportional to the flight altitude, e.i. The lower flight altitude, the higher. Object resolution. The field test data showed the temperature anomaly width appeared on the ground for the petroleum pipe was usually 1-1.5m at night. Considering the safety of aircraft flying at night, we selected 600m as imaging flight altitude. The ground resolution (d) was 1.5m. So, the pipe anomalies usually cannot be missed, and the result was as good as expected.
The selection of normal temperature range: DS-1230 quantitative double-channel infrared scanner with two blackbodies as reference source can control the upper and lower limitation of the received temperature signal. According to the ground test data and the signal in the flight, we selected BB2=-2°C (the upper limit temperature), BB1=-15° (the lower limit temperature) for imaging. In this way, the radiant temperature from different objects on the ground on the ground was in the range. The upper limit of the normal temperature range is a little higher than practical need, in order to stick out the pipe anomalies in the relatively dark background of images.
Image interpretation and test results
The ground radiant temperature signals received by the airborne imaging scanner were recorded on the high-density tapes. The recorded information was transformed by a special image processing system into black-and-white analogic images or digital colour images for the purpose of visual interpretation. The night-scanning infrared images are used for image interpretation, with the reference of colour infrared pictures, topographic maps and the petroleum pipe distribution maps. In the procedure of interpretation, the image interpretation keys were set up in the first place, to eliminate all kinds of object interference factors such as high way, channel, ridges and other linear objects. Then, the interpreted pipes were accurately positioned, and transferred to 1:10000 topographic map. The last products were the interpretation map of petroleum pipe distribution.
The petroleum pipe interpretation keys: The petroleum pipe anomalies have white-tone linear display on thermal infrared black-white analogic images. The geometric characteristics are in straight lines and turned lines, some of them in winding or arc lines. Most of them are in bunching on plane distribution, or in radiant ray shape linked with well sites and with the calculation stations and oil-transferred station as centers. (See page, 6, Fig.3 and Fig.4)
After image interpretation and map compilation, 364 lines of pipe were found in the 108Km2 area. Comparing the image interpretation maps with the pipes distribution maps, there are 8 lines of pipes with different location, and 17 lines of pipes without display. The field test and verify proved that the image interpretation maps are accurate. Most of the 17 undisplayed pipes are abandoned pipes; unused pipes or water supply pipes with normal temperature and natural gas pipes. Gerelly, the test was successful with expected results.
Conclusion
- The test successfully proved that the airborne thermal infrared remote was a new efficient technology for petroleum pipe detection, and can be used in production.
- The test result showed that the selection of imaging season, imaging time, flight altitude and the normal temperature range for the thermal infrared remote sensing investigation was reasonable. The effectiveness of test was good.
- The advantage of airborne thermal infrared remote sensing for petroleum pipe detection are: visualization, easily-positioned and convenience for comparison; It is not limited by access Its cost is lower than the other ground geophysical methods.
This investigation is a experiment of production. It is believed that the technology will produce great social and economic benefits.
References
- F.F. Sabin: the Principle of Remote Sensing and Interpretation the Geological Press, 1981.
- Zhou Yanru: Airborne Thermal Infrared Remote Sensing Images Collection, the Geological Press, 1988.,
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