Describir: Tendency in the development of small-sacle photogrammetric mapping.

 ______     _____    _    _      ___     __   __     ___      _  _      ___    
|      \\  |  ___|| | |  | ||   / _ \\   \ \\/ //   / _ \\   | \| ||   / _ \\  
|  --  //  | ||__   | |/\| ||  / //\ \\   \   //   | / \ ||  |  ' ||  | / \ || 
|  --  \\  | ||__   |  /\  || |  ___  ||  / . \\   | \_/ ||  | .  ||  | \_/ || 
|______//  |_____|| |_// \_|| |_||  |_|| /_//\_\\   \___//   |_|\_||   \___//  
`------`   `-----`  `-`   `-` `-`   `-`  `-`  --`   `---`    `-` -`    `---`