USGS is reporting that substantial parts of Japan have shifted 8 feet because of the earthquake and the earth's axis has tilted a few inches.
Eight feet (I believe) may be sufficient to foul up some of the more precision applications of GPS. It is within the public-available standard of error, but for instance don't surveyors use military-quality GPS along with a ground-based radio system?
It would certainly be confusing if one owned an old fence line and suddenly the fence is 8 feet into the neighbor's property.
Found some discussion here. There may be more authoritative discussion, but "GPS" and "Japan Shift" are in too many news web articles today to make it an easy search. (USGS used the word GPS in their announcement).
http://forums.groundspeak.com/GC/index.php?showtopic=270163
The axis shift of the Earth is probably less significant, but wonder about the geometry of that. A slight axis shift might dislocate GPS measurements a fair distance near the equator? The axis would shift but the GPS satellite orbits would not shift?
The article above describes that there is slow tectonic drift and natural earth wobbles which account for several feet drift per decade just about everywhere. So an old GPS map might not be extremely accurate anyway. For precision use, seems that GPS maps would need relatively constant updating?
Eight feet (I believe) may be sufficient to foul up some of the more precision applications of GPS. It is within the public-available standard of error, but for instance don't surveyors use military-quality GPS along with a ground-based radio system?
It would certainly be confusing if one owned an old fence line and suddenly the fence is 8 feet into the neighbor's property.
Found some discussion here. There may be more authoritative discussion, but "GPS" and "Japan Shift" are in too many news web articles today to make it an easy search. (USGS used the word GPS in their announcement).
http://forums.groundspeak.com/GC/index.php?showtopic=270163
The axis shift of the Earth is probably less significant, but wonder about the geometry of that. A slight axis shift might dislocate GPS measurements a fair distance near the equator? The axis would shift but the GPS satellite orbits would not shift?
The article above describes that there is slow tectonic drift and natural earth wobbles which account for several feet drift per decade just about everywhere. So an old GPS map might not be extremely accurate anyway. For precision use, seems that GPS maps would need relatively constant updating?
