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Poster Session Q
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A study on the application of aerial Remote Sensing technique to calculate uncultivated coefficient of cropland in Tibet
- The Plan for Calculating Uncultivated Ceofficients Indoors by the Use of Aerial Photographs
- Calculating uncultivated coefficient by computer automatic classification.
The IRSA-II and I2S-101 image processing systems were used to classify the digitized aerial photographs supervisoryly and discriminate the cultivated lands from uncultivated ones. Then the rations of these kinds of land are calculated.
Using this method, we could determine uncultivated coefficients accurately when uncultivated lands was bare or sparsely covered with grass.
- Uncultivated coefficient calculation under microscpo
Using ten-time aerial measurement microscope, we measured the length of cultivated and uncultivated parts of the sample lands. Then uncultivated coefficients can be got from tills measurement
Because of manually enlarging and discriminating , this method can be used to treat every kind of lands, However the accuracy of this method is poorer than the two formers. This is not only because both the power of the magnifying glass and the smallest scale are definite, but also because the results are worked out by statistics.
We compare the results gained by the three indoor methods above with results gained by measuring in site. The accuracy analysis of these three methods are shown in Table 2.
Table 2. Accuracy analysis results by comparing uncultivated
coefficients measured indoors with data measured in site.
TABLE 2 IS MISSING PAGE Q_3_4
From Table 2, we can see that the largest difference of each method is less 4%, satisfying the technical demand.
In order to reduce the effect of topographical project, we used long-length camera; in addition, we selected those, which were near the main focus on the photographs as sample lands.
- Discriminating geomorphologic condition and types of cultivated lands, editing indexing table
After the uncultivated coefficients of all sample lands were obtained a study on the method of using sample photographs to calculate the uncultivated coefficients for every pieces of cropland was carried out. The study is described in the following two aspects.
- Establish an indexing classification system.
As an indexing classification system, it should include all kinds of cultivated lands in the investigated region. And every element, included in the system, should be distinguished early in the aeira photographs. So we set up an indexing classification system as Table 3 shows.
Using the three methods described above, we determined the uncultivated ceofficients of 600 pieces of sample fields. Therefore, every column of each grade contained numbers and uncultivated coefficients of 10-20 pieces of sample fields.
- The sampling color infrared photographs and indexing tables of every prefecture
According to the in-situ investigation and discrimination of aerial photos, we determined the second grade-classified types of every prefecture. Considering the demands of classification system, sample lands of different prefecture were selected according to its own condition. These samples were selected from the cultivated lands whose uncultivated coefficients have been calculated. Also it was required that the samples had enough numbers. Then, according to the demand of each prefecture, the sample photographs were made into copies. By matching the indexing tables of uncultivated coefficients with their corresponding photographs, a complete comparing indexing system of uncultivated coefficient was set up.
TABLE 3. IS MISSING PAGE Q_3_5
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