My initial attempt at merging the contours I got from Menlo Park, and the aerial image I snagged from Terraserver has pointed out a few weaknesses with AutoCAD, and the need, as I anticipated, to use other, more capable programs.

The first limitation is that even though both the contours and photo have coordinates associated with them, they are different coordinate systems (state plane vs. WGS-84), and not only does ACAD 2005 provide no means of converting between the two, it completely ignores any coordinates associated with raster images (GeoTIFF images or TIFF/JPEG images with a world file). I’ve manually overlaid the photo, scaling and rotating it to get it close enough to do some initial planning, and to confirm that vanilla AutoCAD isn’t the right tool for this task.

The second limitation is a great example of AutoCAD’s lack of built-in support for 3D input devices. First, since the controller’s action is grafted onto AutoCAD, every movement of the controller pollutes the command line and the undo history with its commands, and when you stop moving, the display flashes annoyingly as AutoCAD’s “real” view is updated to match.

Second, the performance of the realtime 3D viewing sufferes dramatically once the image is attached—even if I unload the image to remove it from the display and memory. Even on my 3.0 GHz Pentium 4 and GeForce FX 6500 graphics card, the slowdown was enough that I had to revert to a version of the file without the image attached to check the contour file.

The great thing about the SpaceBall is the ease with which it lets you change your perspective. I found gently twisting the drawing around in 3D allowed me to quickly find contours that had the improper elevation and fix them. Although when I needed to highlight an out of place contour and then change the view again to get a better perspective, the highlighting disappeared—also an artifact of AutoCAD not having built-in support for the SpaceBall.