danames wrote:
Lines are defined by vertices. So if you line only has two end points then it will always appear as a straight line in any projection. However, if you line is defined by a series of vertices in one projection, then when you reproject, you may get a curved line. In the example below I drew two lines roughly between Los Angeles and New York using WGS84 GCS projection. One is defined by two points, and the other by a series of vertices. When I reproject the data into UTM NAD 83, Zone 14N, then you can see that one line is still straight but the other becomes curved.Actually, what I was trying to achieve is not quite like your example. If I was to draw a line between LA and NY using WGS84 projection, I would expect the line itself to appear curved to the north, to follow the great circle line. If you define a straight line ON THE SCREEN between LA and NY using WGS84, and put more intermediate vertices on it, that wouldn't be the shortest line between the two points, and also wouldn't reproject correctly as a great circle line in other projections, just as in your example you're not getting a great circle line when reprojecting. That could be achieved, but only if you draw the original line in a gnomonic projection, which projects a great circle as a straight line.
I hope this helps.