Lately I've been experimenting with GIS data using Frank Warmerdam's shapelib and Gerald Evenden's projection library called libproj4.
I'm toying around building a Cocoa application to show SHP data (read maps).
The projection library comes in handy as it makes it very easy to apply a certain projection type to your data.
I'm somewhat confused about some of the things that happen to a projection when you change the first parallel (e.g. to 90W) as some of the points wrap up to the other side and I get weird artifacts when drawing. If this was in three dimensions I think it would be solved by taking into account the orientation of the normal to the surface being drawn but in 2d the normal is not there.
This is probably caused by lack of understanding of how projections work and I'm thinking I probably have to change the origin of the coordinate system used when drawing.
More on this later...
I'm toying around building a Cocoa application to show SHP data (read maps).
The projection library comes in handy as it makes it very easy to apply a certain projection type to your data.
I'm somewhat confused about some of the things that happen to a projection when you change the first parallel (e.g. to 90W) as some of the points wrap up to the other side and I get weird artifacts when drawing. If this was in three dimensions I think it would be solved by taking into account the orientation of the normal to the surface being drawn but in 2d the normal is not there.
This is probably caused by lack of understanding of how projections work and I'm thinking I probably have to change the origin of the coordinate system used when drawing.
More on this later...