Hi all, I have been skimming all the dial stuff lately and have seen a few comments on using GPS and Compasses for orienting sundials. On my first experimental dials I used a puck type marine hand bearing compass for alignment. I live on a hill and was able to sight to a distant object that was directly east after correcting for the magnetic variation. This happened to be a restaurant about a mile away. To align the dial (a horizontal with a square base) I just sighted along the edge of the dial to the same spot. This seemed to work ok. I figured the error using this method was probably about as good as you could do with a compass.
I think that a similar technique using a GPS might give a reasonable alignment. In my case where I live on a hill and have unrestricted view (on a clear day) of sometimes 30 miles to distant peaks in the local hills and mountains, I think that the accuracy of gps would be good enough if I "locate" myself on a distant hill and have the gps calculate the bearing to my home location. The reciprocal bearing would be observed from my back yard and could be used to align a dial. The assumption of course is that the gps position error would generate a pretty insignificant bearing error if the base line distance to the identifiable peak is large when compared to the probable position error. To reduce the error to a minimum one would use two gps units simultaneously one at each location and with the judicious use of a cell phone to effect simultaneity, one could minimize the total differential error. A topographical map could also be used for alignment without actually involving a hike to the peak. For later dials (most vertical declining) I observe the time when the rising sun just grazes the surface of the dial location. This is easy and accurate. Dials are forever, Bob 33N 117W
