----------------------------Original message---------------------------- We've got most of Snyder's USGS publications, have implemented many of his methods, and have source from most of the generally available projection programs on the Internet. Looking specifically for references on: 1. Projection interruption. Is this as simple as we think? 2. Drawing lines/polygons across projection boundaries. Have seen GMT's methods, wondering if there's a reference and any experience with efficiency of implementation ( i.e., do it when you apply projection, do it at draw time, etc.) 3. Controlling field of view for Tilted Vertical Perspective projection. In Snyder's book the pictures had to have more parameters controlling the drawing than the projection parameters listed. Intuitive/reasonable ways for controlling how much of the projected view is displayed? _______________________________ Steve Mykytyn -- [log in to unmask] -- voice 415.491.1770 -- fax 415.491.1251 --