On March 17, 2008, the ground synchronous observation test for Landsat TM was carried out in the biandukou intensive observation area. The purpose of the test is to explore the spatial variation characteristics and laws of sub-pixel spectrum of ground objects through the grid spectrum measurement results of ground objects, and analyze the spectral characteristics of ground objects in cold and arid areas. On this basis, it provides data for the spectral model database of typical ground object target and background model, and provides basic data for remote sensing image simulation and spatial scale conversion of remote sensing data.
The measured parameters include: spectral data, surface temperature, atmospheric parameters, soil profile weight and water content (0-1cm, 1-3cm, 3-5cm), surface soil freezing and thawing depth and soil roughness. The time range is about 11:10-13:30.
ASD FieldSpec frtm (Boulder, Co, USA) is used as the spectrum measuring instrument. The spectrum range is 350nm-2500nm. The spectral resolution is 3nm in the visible near-infrared band and 10nm in the short wave infrared band.
The data is in ASCII format and can be opened by Notepad, WordPad and other software. The first 5 lines of the file are the file header, which describes the relevant information of the data; The next two columns of data, one for wavelength and one for reflectance (percent reflectance). The file with suffix. TXT in the original folder is not reflectivity, but an intermediate file for calculating reflectivity. The file in the original data is in ASD's own format and opened with ASD viewspec software.
This data set includes 9 files: TM data, solar spectrophotometer measurement data, Biandu port B1 sample measurement data, Biandu port B2 sample measurement data, Biandu port C1 sample measurement data, Biandu port G1 sample measurement data, Biandu port W1 sample measurement data, Biandu port W2 sample measurement data and ground object spectrum data.
The quadrats for ground synchronous measurement include Biandu port C1, Biandu port G1, Biandu port W1, Biandu port W2, Biandu port B1 and Biandu port B2. Quadrat types include grassland, wheat stubble, deep ploughing and rape stubble. Select the center of the area to lay the quadrat in a flat and homogeneous area. Select 90m respectively × 90m、450m × 450m is used as the grid sampling area of three different scales. At 90m × 90m、450m × 9 will be used in 450m quadrat area × 9 grid division, so that the three quadrats are divided into 81 10m × 10m、50m × 50m sub grid. The specific meaning of the three grids is: 30m × 30m、150m × 150m is the basic resolution of satellite sensor. On this basis, the contribution of single pixel and eight neighborhood pixels to the central pixel is considered. Each pixel is divided into 9 sub pixels to explore the law between the sub-pixel spectrum and the whole pixel spectrum. Due to the long distance between sample points, 90m × The 90m quadrat is realized by laying the quadrat with measuring rope and marker post, with a height of 450m × The 450m quadrat is realized by laying control points with GPS.
The sampling method is profile measurement, which represents the spectrum of the whole quadrat pixel by measuring the central profile of each sub quadrat, and replaces the full sampling of the sub quadrat by measuring the statistical average of the spectrum for many times. The survey route adopts tour mode, which can save manpower and material resources to the greatest extent, speed up the spectrum measurement speed and ensure the quasi synchronization of spectrum measurement.
The water content measurement method is: take 0-1cm, 1-3cm and 3-5cm soil samples and put them into self sealing bags. The measurement method of soil freezing depth is to judge the freezing depth by inserting chopsticks into the surface to feel the soil hardness or directly digging out the frozen layer on the surface of the soil to measure the thickness of the frozen layer. Measured directly with a ruler, when the soil hardness is large and there are ice crystals, it is considered that the soil is frozen; On the contrary, it is considered that the soil is not frozen. Data can be opened with Microsoft office software.
Good data quality
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CSTR:11738.11.ncdc.NIEER.2021.1944
10.12072/ncdc.NIEER.db1891.2022