1. -- the_geom 自带 投影坐标 4326
    2. -- 17.3    图斑数据中的面积 
    3. SELECT jcmj FROM "spot_meta_v2" WHERE jcbh = '6209822021062907223962';
    5. -- 直接计算面积（平方度、万平方千米）后换算 st_area(the_geom) * 1500 * 10000
    6. -- 18.2896541856215  
    7. SELECT st_area(the_geom) * 1500 * 10000 FROM "spot_meta_v2" WHERE jcbh = '6209822021062907223962';
    9. -- 转换投影坐标后直接计算面积（平方米）并换算 st_area(ST_Transform(the_geom, 26986)) / 666
    10. -- 17.3328237816885
    11. SELECT st_area(ST_Transform(the_geom, 26986)) / 666.66 FROM "spot_meta_v2" WHERE jcbh = '6209822021062907223962';
    13. -- 转换地理坐标后计算面积（平方米）并换算 st_area(the_geom:: geography) / 666.66
    14. -- 17.311556754445  
    15. SELECT st_area(the_geom:: geography) / 666.66 FROM "spot_meta_v2" WHERE jcbh = '6209822021062907223962';
    17. -- 其他投影方式
    18. -- SELECT st_area(ST_Transform(the_geom, 2249)) * 0.3048 ^ 2 / 666.66 FROM "spot_meta_v2" WHERE jcbh = '6209822021062907223962';