2 replies to this topic

[christine.skl]

Hello,

I am doing my undergraduate thesis now (3D Interactive map of World Natural Heritage) . Right now I am doing the database of the points I want to include on my map, and here a question came to my mind. A lot of points on my map are large areas like national parks, in the resources I use, I have their geographical coordinates, just like: "Canaima National Park, 5deg 20min N 61deg 30 min W". The coordinates are a point. How this point is defined (is it the middle of the area, certain side of the area etc)?. After 4 years of working with GIS I realised that I don't know these basics. Strangely, I didn't find anything in my cartography class book, neither in my other references. Please help!

Thank you:)

Christine

[David Medeiros]

Hello,

I am doing my undergraduate thesis now (3D Interactive map of World Natural Heritage) . Right now I am doing the database of the points I want to include on my map, and here a question came to my mind. A lot of points on my map are large areas like national parks, in the resources I use, I have their geographical coordinates, just like: "Canaima National Park, 5deg 20min N 61deg 30 min W". The coordinates are a point. How this point is defined (is it the middle of the area, certain side of the area etc)?. After 4 years of working with GIS I realised that I don't know these basics. Strangely, I didn't find anything in my cartography class book, neither in my other references. Please help!

Thank you:)

Christine

In a GIS this would usually be a centroid, determined by the software applying a bit of geometry to your polygons to get an averaged center point. In real life these may have just been eyeballed by the person doing the digitizing.

http://en.wikipedia.org/wiki/Centroid (sorry for the wikipedia entry, I am sure there's a better explanation somewhere).

[christine.skl]

Thank you, your explanation gives me the idea:)) especially after quite a bit of those points in the datatbase:) Wikipedia will do in early morning hours of GMT +8 time zone!