- 1. Coordinate(坐标) data for GIS
- real coordinate system:Cartesian coordinate systems(笛卡尔坐标系)
- from 3D to 2D, the earth can be modled as a sphere(球体), oblate ellipsoid(扁椭圆体), geoid(大地水准面). We need a cartographic projection(地球投影),a datum(基准面) to do this.
but there always a trade off
- 2. datum
- a. the first national horizontal datum: Australian Geodetic Datum (AGD66) in 1966
- b. new Geocentric Datum of Australia 1994 (GDA94)
- c. a new one is gonna coming in 2020
- #Converting between projections: transform data to a common cartographic projection
- 3. GDA94
- units:metre
- UTM projection
north+east: 等角横轴割圆柱投影, 圆柱投影是将一个圆柱面包围椭球体, 并使之相切或相割, 再根据某种条件将椭球面上的经纬网点投影到圆柱面上, 然后, 沿圆柱面的一条母线切开, 将其展成平面而得到的投影. 其中正轴圆柱投影的圆柱轴同地轴重合, 横轴圆柱投影的圆柱轴同赤道直径重合, 斜轴圆柱投影的圆柱轴同地轴和赤道直径以外的任一直径重合.
false easting(东伪偏移): 投影平面中为避免横轴 (经度方向) 坐标出现负值, 而所加的偏移量
false northing(北伪偏移): 投影平面中为避免纵轴 (纬度方向) 坐标出现负值, 而所加的偏移量
4. GLONASS: 全球导航卫星系统, used to know location without gps
- 5. metadata
- data quality can not be changed from general to specialize, but otherwise is fine. for example, if we got the data quality of a 30*30, we do not know the data quality of a 5*5, but otherwise we will know the data quality of 30*30 if we know the data quality of 5*5
6. data dictionary 简单记录了我们所需要的数据, 但不是所有信息(在该地点考察并记录, 可能包含一些估计值)
metadata 包含了如何制作数据(如何制造这个地图)
- 7. meta data standard: ISO
- 8. spatial information: triangulation or gridding
来源: http://www.bubuko.com/infodetail-3092662.html