Scott:
1. What have people found to be the most accurate measurement of elevation. Thanks.
Hi Marian,
For what it's worth, here is my experience, adding to what Scott said: if I remember correctly, the best res on the DEM model is a point roughly every 100 feet. That in itself can lead to a significant error. In general, here in the NW, my guess is that plus / minus 50 ft is the best the DEM can do. Sometimes it's much worse. On the other hand, when the GPS gets a good, unobstructed view of the sky, I've been amazed at the accuracy. On many of the peaks in the Cascades where where I have compared the elevation reported by the GPS to the transit elevation, or the elevation of a benchmark, I often get agreement within five feet! This even though the GPS says that the best it can do is say 12 feet. On the other hand, in deep forested valleys, the GPS elevation data can be near worthless. One clue to this in the field is noticing that the GPS elevation data lags. (That is, when you arrive at a point of known elevation, the
GPS reports the elevation you attained earlier.)
Hope this helps,
Larry