Newsgroup sci.engr.surveying 3874

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In article <19970101155800.KAA12209@ladder01.news.aol.com>
           levsurvr@aol.com "LEVSurvr" writes:
> Mark, I have been using a Geotronics System 4000 for over 4 years. The
> advantage over the System 600 is that you can direct the area of "vertical
> search" by use of the telescope on the remote unit. Geotronics does not
> now promote the 4000, but it is still available. I believe it is also more
> durable under field conditions. I do not like the idea of cables etc. when
> working in brush
> 
> Regards,
> 
> Larry E. VanOsdol, LS
> 120 West LaSalle Avenue, Suite 304
> South Bend, IN 46601
> 
Larry, 
On the latter point about cabling, I tend to agree. Working through
overgrown areas with  the robotic system is somewhat frustratiing at
times.
The inability to reset the vertical search area is a bad ommission 
on the manufacturers part. I believe that the search facility of the
instrument is only just adequate at best. What I thought would have 
been the most obvious faclity would to be able to directly drive the
vertical and horizontal planes from the remote keyboard. I am sure
that this would be a real boost to the search facility, especially
on sites with a large vertical displacement.
In its defence, I am generally pleased with it, and on flat sites,
the search facility works well, bad thats the ideal situation.
-- 
Regards
Mark Johnson

Survey quality DGPS will require a reference base station set over
your marker if you expect to be able to read on the order of a 1 cm
over your property.  You will also need some precise angular reference 
(another known reference).  If these references are only known by
latitude and longitude, you will need an accuracy of about 3 thousanths
of an arc second
If you have dgps service from a dgps provider such as DCI or OMNISTAR,
the best you can expect is a few meters accuracy. See:
   http://www.cnde.iastate.edu/staff/swormley/gps/dgps.html
If your marker is known to the nearest second of arc, then you know
the location to 100 feet or so. 
__________________________________________________
Sam Wormley - http://www.cnde.iastate.edu/gps.html