Remote Sensing Image Data

Image Data Basic Concepts

Image Data is an image obtained by an imaging system on a satellite or an airplane, and most of the images are remote sensing image data. Each pixel of Image Data has a value, which represents the electromagnetic radiation intensity of the target on the ground area corresponding to the pixel detected by the sensor, also known as brightness value and gray value. Image Data formats supported by SuperMap are: *.img, *.tif, *.tiff, *.bmp, *.jpg, *.png, *.gif, *.raw, *.sid, etc.

The computer records data in binary, so the level of quantization is in binary, that is, 2 n . If n bits are used to record each pixel, its gray scale value can range from 0 to 2 n-1, for example, 8-bit data takes 28 = 256 gray scale levels (its value ranges from 0 to 255); If one bit is used to record each pixel, its gray value is only 0 and 1, that is, the so-called binary image. If a color system is used to record an image, according to the principle of colorimetry, any color can be synthesized by the three primary colors of red (R), green (G), and blue (B) in a proper proportion. If an 8-bit RGB color coordinate system is used to record a pixel, 224 different RGB combinations can be recorded. If the brightness values of RGB are 0, 0, 0 respectively, a black pixel is generated; if the brightness values of RGB are 255, a white pixel is generated; and if the brightness values of RGB are equal, a gray effect is generated.

Remote Sensing Imagery imaging mode

The imaging modes of remote sensing Image Data mainly include aerial photography, aerial scanning and microwave radar.

  • Aerial photography: Photographic imaging is the technology of obtaining images of objects through imaging equipment. Traditional photographic imaging relies on optical lens and photosensitive film placed in the focal plane to record the image of the object. Digital photography records the image of the object with digital signals through the light/electricity conversion of the photosensitive element placed in the focal plane. The detection bands include near ultraviolet band, visible band and infrared band.
  • Aerial scanning: Scanning imaging is based on the point-by-point and line-by-line sampling of the instantaneous field of view of the target object by the detection element and the scanning mirror, so as to obtain the electromagnetic radiation characteristic information of the target object and form an image of a certain band. The detection bands include ultraviolet, infrared, visible and microwave bands.
  • Microwave radar: The operating wavelength of the microwave imaging radar is 1mm-1m microwave band. Since the microwave radar is an active sensor with self-contained energy, and the microwave has the ability to penetrate clouds, the microwave radar imaging has the characteristics of all-day and all-weather. In urban remote sensing, this imaging method is of great significance for the identification of targets sensitive to microwave. At the same time, microwave has a certain ability to penetrate ice, snow, forest and soil, and has special significance for ocean remote sensing. The detection band includes microwave band and infrared band.

Remote Sensing Space Platform

Space Remote Sensing Imagery satellites are divided into three series: land satellites, ocean satellites and meteorological satellites. The details of each type are as follows:

  • Landsat series: For the purpose of exploring land resources, this type of satellite is characterized by multi-band scanning with a ground resolution of 5-30 m. At present, the main land resource satellites are: Landsat, SPOT, IRS, CBERS, JERS, IKONOS, QuickBird, etc.
  • Ocean Satellite Series: The world's ocean satellites include ocean color satellites, ocean topography satellites and ocean environment satellites. At present, the main ocean satellites are: Radarsat satellite of Canada, ERS satellite of Europe, Seasat satellite of the United States, etc.
  • Meteorological Satellite Series: Meteorological satellites are widely used in the national economy and military fields, and can continuously, rapidly and widely detect global atmospheric changes. The orbit of meteorological satellite is divided into low orbit and high orbit, with short-period repeated observation and strong real-time. At present, the main meteorological satellites are NOAA satellite of the United States, GMS meteorological satellite of Japan and FY meteorological satellite of China.