What do you mean by three-tone spots?

The third national land survey (formerly known as the third national land survey) is the third national land survey.

Taking the standard date of 20 19 12 3 1 as the standard time point, the "three surveys" comprehensively investigated the current situation of land use in China, established a land survey database covering national, provincial, prefectural and county levels, and comprehensively grasped the data of major land types in China.

"Three Tunes" is a survey of major national conditions and national strength, and it is also a unified survey of natural resources after the reform of the party and state institutions. Its data results can comprehensively and objectively reflect the land use situation in China, as well as the problems existing in farmland protection, ecological construction, and economical and intensive land use.