How do I draw a graticule in GIMP?

[Gidde]

I usually use the path tool for graticules, straight or curved; that allows the greatest range of line types (and allows you to change your mind if you hate the dashed line).

[HTBrown]

I played with it this morning, and found an answer that works for this problem. If you zoom in to 1600%, you can locate points to a fraction of a pixel. There's a scale that appears along the left and upper edges that tells you exactly what coordinate you're at - if I'd noticed that earlier I wouldn't have bothered you all with the question! . A little quality time with a spreadsheet told me where I wanted the lines, and then I used the path tool to place them precisely. If I was using a projection with curved lines, I could, in principle, do the same thing, though it might become tedious.

Thanks for the answers!