- let define the raster image size, say: 1800x900 pixels
- I want draw my own raster image map - by drawing polygons e.g. like "draw line from pixel with coordinates x100y100 to pixel x100y103"
- it is easy to convert the dataset geographic-coordinates to pixel coordinates
- can choose from 3 datasets, each have different scale
The question is:
- how to choose the needed dataset (so how to choose the needed map scale)
- to draw the map of the given real dimension (e.g. whole earth, or area of 2000x1000km)
- with minimalizing multiple drawing of the same line e.g. to minimalize subpixel coordinates?
Probably the question is badly formulated, so trying it explain more precise:
- having the earth "width" is approx. 40.000km.
- e.g. for the image of the width 1800 pixels, 1 pixel is 22km.
- So, drawing the world map to 1800x900 image from any data what has higher "resolution" than 22km/pixel is pointless, because will need to draw a line from a pixel coodinates x100y100 to x100y100 (e.g. from the given pixel to the same pixel, because the map data is unnecesary too much precise and after the conversion to pixels the result gives the same pixel)
- so, how to determine the needed dataset scale?
Hope now it is more clear - sorry, my english is not my native...
I was read many questions here, like:
- Dimensional analysis/conversion problem: Map scale to image resolution (dpi)
- How to Determine to world map size in pixel given this data?
- Mapserver, TMS, Scales zoom levels and how to deal with all of it
- and many others - but still don't figured out an reasonable "algorithm".