Comprehensive survey of aerial remote sensing

Remote sensing flight is an important part of remote sensing work, and the flight quality directly affects the effect of aerial remote sensing application. The system design should be carried out according to the research content and its accuracy requirements, the geographical and geomorphological conditions and technical conditions of the working area, and the best benefits can be obtained with less manpower, material resources and financial resources.

3.2. 1. 1 remote sensing flight design

In remote sensing flight design, the following issues are mainly considered:

(1) flight platform and sensor selection. The selection of aerial remote sensing flight platform should consider the low altitude, low speed, automatic navigation, stable performance, flexibility and portability of the aircraft. At present, Mi Ba, Shuang Otter, An-12, Il-14 and other aircraft used for aerial remote sensing flight in China can meet the requirements. The sensor should be based on the image to be acquired. For remote sensing of mining resources and environment, two kinds of sensors can be used: photography and scanning. RC- 10 aerial camera has the advantages of large image frame, small distortion and high lens resolution. The automatic exposure part has high sensitivity to the compensation control of panchromatic, infrared, color and color infrared photographic images, and can directly obtain panchromatic, true color and color infrared photographic images. In order to study the thermal field in mining area, airborne thermal infrared scanner is needed. The working band of JHY-2 thermal infrared scanner made in China is 8 ~ 14μ m, the spatial resolution is 1mrad, and the temperature sensitivity is 0. 1℃, which can completely meet the requirements.

(2) Selection of image scale. In the multi-band, multi-phase and multi-window aerial remote sensing flight, the main scale is determined by the main research content and the highest precision requirement (resolution). In the study of remote sensing in this mining area, photographic means must meet the accuracy requirements of aerial mapping to ensure the positioning accuracy of large-scale series mapping. The positioning of other scanned photographic images is unified on the main scale image.

When choosing the scale of aerial remote sensing photography, a principle to be considered is whether the smallest ground elements can be identified. For 2m×2m ground objects, the image size on a good image should be greater than 0.2mm, and the image scale should not be less than110000. In addition, the scale should be selected from the size of the dead angle of building photography. As shown in figure 3-2, there is a building with a height of h at the distance from the zenith R. A photographic blind area with a width of r=hR/(H-h) will be created on the ground on the side of the building far from the zenith. Through a simple transformation of this formula, the scale of aerial images can be reversed, that is,

Study on environmental dynamic monitoring and analysis in industrial and mining areas

Figure 3-2 Schematic diagram of photography blind area

If the building is generally not too high, five to seven floors, with an average height of 15m. If it is required that the dead zone of R = 300m photography is not more than 3m, the flying height is:

h = 15(300+3)/3 = 15 15(m)

So the image scale is:

1/M = f/H = 0. 152/ 15 15≈ 1/ 10000。

Where f is the focal length of the camera (in m).

From the above analysis, it can be seen that different objects of remote sensing research should have different imaging scales, and finally the best scale must be selected by integrating various factors. In this flight, the main scale was determined by color infrared photography. Considering the need of updating the topographic map of the mining area and the main functions of aerial remote sensing, the imaging scale was finally determined to be 1∶5000.

(3) Requirements for image resolution and photo overlapping rate. Whether the ground target can be detected and identified mainly depends on the ground resolution of the image or the minimum ground interval (m). Ground resolution depends on image resolution and image scale, namely:

Study on environmental dynamic monitoring and analysis in industrial and mining areas

Where d is the minimum ground distance (m) and r' is the resolution of aerial photos (line pair /mm). It can be seen that different image scales and image scale combinations will produce different ground resolutions to meet different remote sensing survey needs. Because the aerial photograph takes the center as the projection point, its geometric characteristics and low platform photography will cause large displacement of the image point, and the resolution of the center image and the edge image is quite different. As far as the focal length of the camera is 152mm, the resolutions of the center and edge images are 100 line pairs /mm and 30 line pairs /mm, respectively. Therefore, for the color infrared aerial photograph with the scale of 1: 10000, the ground resolution is 0.05 m× 0.05 m, respectively. This resolution can generally meet the requirements of remote sensing application in mining areas.

In order to meet the requirements of geological map of mining area, the overlapping rate of color infrared photography photos in the heading direction is not less than 60%, and the horizontal overlapping rate is not less than 15%, and there can be no loopholes.

Thermal infrared scanning images need edge connection.

(4) Selection of imaging phase and atmospheric conditions. In this study, the investigation of land use status in mining areas is one of the important tasks. In addition to a large area of natural plants, soil, rocks and water bodies, there are many artificially processed ground features, such as cement, asphalt and tiles. In order to fully display the information of various land use types and improve the interpretation efficiency, it is very important to choose the image with the best time phase. Nature is a large ecosystem, and the hydrology, soil and vegetation on the surface are important perspective information reflecting the surface differences. The period with the largest difference is also the period with the largest spectral difference of various ground objects, and it is also the best imaging period for remote sensing investigation of land use status, which is called the best phase. For different climatic zones and natural ecological zones, the optimal phase is obviously different. For North China, the best period should be the middle and late autumn. At this time, woodland, grassland and farmland are the easiest to distinguish. Most crops have been harvested, and it is easy to identify the surface morphology, which is conducive to aerial survey and mapping. In addition, try to choose the season and time when the sun is high. At this time, the shadow of the object is the smallest, the response performance of the sensor is better, and the interpretation performance will be improved.

The influence of atmospheric conditions on the imaging quality in aerial photography can not be ignored. Generally, you should choose to take photos in cloudy weather with high visibility. Previous studies have shown that photos taken on cloudy days with high atmospheric visibility are often better than those taken on sunny days in terms of image clarity, interpretation performance and object outline.

3.2. 1.2 Aerial Remote Sensing Flight

Remote sensing flight is an indispensable and important work in aviation remote sensing research. The quality of flight will directly affect the quality of information obtained. The whole mission includes two stages: color infrared aerial photography and thermal infrared scanning flight.