Re: High Resolution GPS Location and Orientation Mapping

On Jan 3, 7:43 pm, richardalanforr...@xxxxxxxxxxxxxx wrote:
On Jan 3, 7:20 pm, alextangent <b...@xxxxxxxxxxx> wrote:



On Jan 3, 6:34 pm, Seanpit <seanpitnos...@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
wrote:

On Jan 3, 12:07 am, richardalanforr...@xxxxxxxxxxxxxx wrote:

< snip >

Turner, L. E., A. V. Chadwick, and L. Spencer. High Resolution GPS
Mapping In A Vertebrate Taphonomic Quarry. Geological Society of
America. Abstracts with Program 32:A499. 2000.

That reference refers to a single quarry,Sean. You can tell by
*reading* the title. How on earth does that demonstrate widespread
patterns of current alignment? And it doesn't demonstrate that GPS
records orientation.

You said that GPS could only be used for location, not orientation
studies. This particular reference shows that you are wrong in that
notion.

The reference refers to *MAPPING*, something for which GPS is very
useful. It does *not* demonstrate that GPS was used for recording
*orientation*.

Obviously, you didn't read the paper or even the abstract . . .

You also evidently haven't done much work with high resolution GPS
mapping. Using such instruments both location and orientation can be
precisely mapped to within less than 1cm of accuracy.

I know Arthur Chadwick and have gone to his lectures and I know how he
does this sort of mapping. The location and orientation of a bone or
bony fragment along a particular axis can be measured relative to
magnetic north. For larger bones, high resolution GPS (with
subcentimeter accuracy) can be placed on either end of the bone to
determine location and orientation.

wtf? The military can't get better than 17.8 metre horizontal
accuracy, 22.7 metre vertical accuracy using PPS; which isn't
available to civilians, which is in the 100 metre range. Sub cm
resolution? In yer dreams. And GPS isn't a compass (although some of
them have electronic compasses built in).

"A variable number of points (ranging from one for small
fragments or teeth, to many for large bones) were then taken directly
from the exposed bone using a Javad GPS having a resolution of 1 cm or
less."

http://geology.swau.edu/faculty/gps.html

--
Regards
Alex McDonald

Actually, one can measure position with high accuracy using GPS
systems. It requires setting up temporary base stations in the
vicinity of the site being surveyed. There are other techniques, such
as taking thousands or tens of thousands of readings from a fixed site
and averaging the results. This method has been used to measure rates
of tectonic plate movement to the nearest millimeter.

Some GPS receivers have an averaging function built in. Of course, the
technique needs to be calibrated by reference to a known location to
give reliable results, and as accuracy is related to the time during
which readings are made - in measuring plate movements a unit is in
place for up to 24 hours - it is not useful for high-resolution
mapping.

RF

RF

Good point. Still wouldn't be possible given a combination of (a) the
state of the technology in 2001 (b) and a Javad, which is a
*navigation system, not a *surveying system.

--
Regards
Alex McDonald

.

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