At present, there are mainly three methods for surveying various types of land in agricultural divisions at county level: one is the use of topographic maps; the other is the use of aerial photographs for interpretation and transfer; and the third is the use of satellite photographs for interpretation. The improvement of the third method is the land area measuring instrument with GPS function nowadays. Each of the above methods has its own advantages and disadvantages. The land area measuring instrument can be used to accurately and quickly use the modern land area planning work. Measurement.
The aerial photograph interpretation and transfer method has the advantage that the photo image is true and intuitive, and the staff can master the interpretation technique with a little training, and can relieve a large number of fieldwork and reduce the labor intensity. However, the internal painting work is cumbersome and the workload is heavy. There is still no convenience and simplicity of the land area measuring instrument. In addition, the aerial map is the same as the topographic map, and its accuracy varies with the scale. If the scale is large, the workload is large and the scale is small. However, the small scale may not reflect the small class and affect the work accuracy.
The method of topographic map drawing is the most commonly used and most widely used method at present. Its accuracy is affected by people's toxicity (recognition and drawing ability), and mainly varies with the topographic map scale, l: 2,000,000. On the topographic maps, the width of a narrow field of less than 25 meters long, and less than 20 acres of dry land, vegetable fields or other small plots, it is difficult to accurately draw out; 1:5000. In the topographic map, it is difficult to reflect the linear features with a width of less than 50 meters and the land with an area of ​​less than 75 acres. The steps of this method are numerous and not directly measured by the land area measuring instrument.
Although the above three methods are conventional methods in past land area measurement, they have a common defect when they are used in county-level agricultural zoning. It is difficult to ascertain the area of ​​strip-shaped objects and small-scale land types. It is precisely in the survey of land resources that it is the most important. Because this problem has not been solved, the area of ​​arable land cannot be checked, and the area of ​​rivers and roads cannot be clarified. After the agricultural, forestry, and water specialities finish investigating field resources, the consolidation of various types of land area creates contradictions. This is also positive. It promotes the development and widespread use of land area measuring instruments.
The aerial photograph interpretation and transfer method has the advantage that the photo image is true and intuitive, and the staff can master the interpretation technique with a little training, and can relieve a large number of fieldwork and reduce the labor intensity. However, the internal painting work is cumbersome and the workload is heavy. There is still no convenience and simplicity of the land area measuring instrument. In addition, the aerial map is the same as the topographic map, and its accuracy varies with the scale. If the scale is large, the workload is large and the scale is small. However, the small scale may not reflect the small class and affect the work accuracy.
The method of topographic map drawing is the most commonly used and most widely used method at present. Its accuracy is affected by people's toxicity (recognition and drawing ability), and mainly varies with the topographic map scale, l: 2,000,000. On the topographic maps, the width of a narrow field of less than 25 meters long, and less than 20 acres of dry land, vegetable fields or other small plots, it is difficult to accurately draw out; 1:5000. In the topographic map, it is difficult to reflect the linear features with a width of less than 50 meters and the land with an area of ​​less than 75 acres. The steps of this method are numerous and not directly measured by the land area measuring instrument.
Although the above three methods are conventional methods in past land area measurement, they have a common defect when they are used in county-level agricultural zoning. It is difficult to ascertain the area of ​​strip-shaped objects and small-scale land types. It is precisely in the survey of land resources that it is the most important. Because this problem has not been solved, the area of ​​arable land cannot be checked, and the area of ​​rivers and roads cannot be clarified. After the agricultural, forestry, and water specialities finish investigating field resources, the consolidation of various types of land area creates contradictions. This is also positive. It promotes the development and widespread use of land area measuring instruments.
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