HISTARCHer's:

I sent a portion of the HISTARCH thread on GPS to one of our National Park
Service resident experts on the subject -- Steve DeVore, at the Midwest
Archeological Center in Lincoln, Nebraska. He replied with some comments on
accuracy and cost below.

Steve usually teaches a course or two every year on the use of remote
sensing equipment, including GPS. These courses are available to everyone,
not just government types. I see he posted an announcement of his next
course already.

I encourage those of you who are thinking about using GPS in the field, or
any other sort of electronic equipment, to give Steve's course
consideration.

Cathy Spude
[log in to unmask]

----- Forwarded by Cathy Spude/SANTAFE/NPS on 01/09/01 09:14 AM -----

                    Steve De Vore
                                         To:     Cathy Spude/SANTAFE/NPS
                    01/05/01             cc:
                    11:56 AM MST         Subject:     Re[2]: GPS at next SHA?






     Hi Cathy

     Cost and accuracy go hand in hand.  The less costly instruments are
     not as accurate as the more expensive systems.  You also have post
     process the data to get accuracy espoused by the manufacturer.

One has to be extremely careful when using the less expensive systems now
on the market.  I am referring here to the ones less than $500.00.  They
are fine for navigating around but probably only accurate to 10 m with SA
currently turned off.

The equipment in the $1000 to $5000 range can be post processed to within a
couple of meters.

The mapping grade equipment in the $10,000 can get one down to half a meter
with post processing.

The survey grade equipment which is provably of the $20,000 range can be
post processed to centimeter accuracy but it requires a long acquistion
time on the surveyed point.


Without post processing the data, the resulting accuracy is much less.

These are only some of the varibles to consider.  The level of accuracy
also depends on your needs.  If you are using the GPS units to map the
location of a site and its boundaries, the accuracy required is not as high
as in the case where you want to piece plot artifacts.

Elevation is another area of confusion.  At best, the vertical height is at
least twice as far off as the horizontal point.

One also has to use the correct datum system in calculating your location

These are just a few thoughts on the matter.


Steve

______________________________ Reply Separator _________________________________
Subject: Re: GPS at next SHA?
Author:  Cathy Spude at NPS
Date:    1/5/01 9:17 AM




Steve:

There's been a thread on the HISTARCH listserve over the last couple of
days about the use of GPS in the field. The main jist of the debate has
been the cost/accuracy one (nothing new here). However, recently, someone
suggested that there should be a training course in the use of GPS at the
next Society for Historical Archaeology meetings.

Bob tells me that you routinely include GPS in the remote sensing courses
you give. Is there a web site people could go to for this information?

Would you care to comment on the thread? I've attached what I consider to
be the most salient portion of the discussion below. Virgil Noble probably
has the whole thread, as he subscribes to the list, if this is anything
that might interest you.

Cathy

[attachment deleted for the sake of keeping this communication from
becoming huge]