I surveyed the Bob Kerrey Pedestrian bridge this afternoon using my GPSr. These devices are not terribly accurate for this sort of thing, but by doing it twice and eyeball-averaging the two routes, I think it's probably not too far off.
I'll enjoy seeing the aerial/satellite photos show up on Google Maps and see how well or poorly I did. I had no idea that the Nebraska/Iowa border is almost on the eastern shore of the river when crossing the bridge. I had just assumed it was near the middle of the bridge over the water.