shrug-l: Trimble ProXRS VS Trimble GeoExplorer XT

Wed, 19 Oct 2005 09:38:37 -0400

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Holli Brandt:

Having used both handheld (Garmin) and prec-ag (Trimble with multipath 
reducer--a prec-ag unit typically has faster update than a pathfinder-type 
unit, since it is meant for rolling-stock applications, but its output 
cannot be post-processed) WAAS realtime-readout units simultaneously in 
field, and comparing them to some benchmarks and also positions of suitable 
(pavement corner) features on DOQQs (via pad/laptop mobile-map), my 
impression (not a formal study as of yet) is that the overall performance 
is frustratingly variable, but in a good situation (open unobstructed 
field) a conservative figure of 2-3 m is about right (which is a bargain 
considering that the service is free and nearly nationwide).  The problem 
comes with "bad" situations, which are quite common along field edges and 
roadsides -- typical FL regrowth/windbreak treelines located southwards 
(where the WAAS signal is coming from relative to FL), and worst of all a 
powerplant/powerline southwards; the handheld WAAS unit is crocked by both, 
the prec-ag WAAS unit by just the latter.  I have not yet tested such 
receivers in big-tree woods or down in ravines, but would expect to 
encounter trouble at such sites also, based on reports by 
others.  Buildings can also be obstacles for WAAS receivers; the denser and 
taller the buildings, the worse the trouble, unless you are willing to do 
"Harold Lloyd" rooftop stunts.

If you want to try to achieve code-based meter-level positions with 
reasonable reliability, as Tripp Corbin posted, you will likely have to 
find a base station cooperator and use realtime-readout with one of the 
rover units designed for that, or switch to post-proc (esp. for 
submeter).  But for powerline/ravine-crocked situations, you may still have 
to rely on conventional survey tools, or perhaps a GPS+rangefinder system 
from a vantage north of the powerline, or a mining-style relay.

Your plan to rent (or get a try-out period) a GPS system to gage its 
performance under your own situations, before you make a purchase, is a 
good one.  When you get to that point, please drop a line about the results 
to shruglist.

Good hunting,

Jack Jordan
UF-IFAS-CRS

At 07:47 AM 10/19/2005, Tripp Corbin wrote:
>Holli,
>Based on my experience, which has not been with Trimble units, in order to 
>get reliable sub-meter locations WAAS correction is not sufficient. I 
>would only guarantee plus or minus 2 to 3 meters using WAAS alone. In 
>order to get reliable sub-meter positions in the field without post 
>processing, I use either Coast Guard beacons or Omnistar corrections. 
>Otherwise post processing is required.
>
>I hope this helps.
>
>
>
>Tripp Corbin, MCP, GISP
>
>Associate Vice President, GIS/Mapping
>
>ESRI Authorized Instructor
>
>Keck & Wood, Inc.
>
><http://www.keckwood.com/>www.keckwood.com
>
>(678) 417-4013
>
>(678) 417-8785 fax
>
>
>
>Keck & Wood, Inc now offers Introduction to ArcGIS/ArcView training 
>classes. Contact me for more information.
>Currently Scheduled Classes:
>Introduction to ArcGIS I - October 25-26 in Thomasville, GA (Class is 
>sponsored by the <http://www.swgrdc.org/planning.htm>Southwest GA RDC GIS 
>Dept.)
>
>Introduction to ArcGIS II - November 7, 9, & 10 at the 
><http://shrug-gis.info/workshop05>SHRUG Workshop in Tallahassee, FL
>-----Original Message-----
>From: shrug-l-admin@lists.dep.state.fl.us 
>[mailto:shrug-l-admin@lists.dep.state.fl.us] On Behalf Of Holli Brandt
>Sent: Tuesday, October 18, 2005 7:50 AM
>To: shrug-l@lists.dep.state.fl.us
>Subject: shrug-l: Trimble ProXRS VS Trimble GeoExplorer XT
>
>Good Morning Everyone -
>Yes, I am still plugging the forum for information even though I have 
>moved.  Still the best source for information and opinions.
>
>We are going to be completing some field work in the near future and are 
>looking into renting a GPS Unit (trying it out before we buy).  For 
>sub-meter accuracy, the following two units were recommended time and time 
>again, the Trimble ProXRS VS Trimble GeoExplorer XT.  I am aware of the 
>basic differences between these two units, ProXRS has external antennae 
>and differential GPS and the GeoXT has internal antennae and WAAS.  I know 
>which way I am leaning but would like to hear what any of you have to say 
>before I commit.
>
>Any personal opinions or criticisms about these units?  Which do you 
>suggest?  Any other GPS unit you prefer?
>
>
>Thanks - Holli
>
>
>Holli M. Brandt
>Project Manager
>EnVetCo
>500 S. Independence Blvd
>Suite 200
>Virginia Beach, VA 23452
>(757) 518-8491
><blocked::mailto:brandth@tesorocorp.com>brandth@tesorocorp.com
>

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Holli Brandt: 
Having used both handheld (Garmin) and prec-ag (Trimble with multipath
reducer--a prec-ag unit typically has faster update than a
pathfinder-type unit, since it is meant for rolling-stock applications,
but its output cannot be post-processed) WAAS realtime-readout units
simultaneously in field, and comparing them to some benchmarks and also
positions of suitable (pavement corner) features on DOQQs (via pad/laptop
mobile-map), my impression (not a formal study as of yet) is that the
overall performance is frustratingly variable, but in a good situation
(open unobstructed field) a conservative figure of 2-3 m is about right
(which is a bargain considering that the service is free and nearly
nationwide).&nbsp; The problem comes with &quot;bad&quot; situations,
which are quite common along field edges and roadsides -- typical FL
regrowth/windbreak treelines located southwards (where the WAAS signal is
coming from relative to FL), and worst of all a powerplant/powerline
southwards; the handheld WAAS unit is crocked by both, the prec-ag WAAS
unit by just the latter.&nbsp; I have not yet tested such receivers in
big-tree woods or down in ravines, but would expect to encounter trouble
at such sites also, based on reports by others.&nbsp; Buildings can also
be obstacles for WAAS receivers; the denser and taller the buildings, the
worse the trouble, unless you are willing to do &quot;Harold Lloyd&quot;
rooftop stunts. 
If you want to try to achieve code-based meter-level positions with
reasonable reliability, as Tripp Corbin posted, you will likely have to
find a base station cooperator and use realtime-readout with one of the
rover units designed for that, or switch to post-proc (esp. for
submeter).&nbsp; But for powerline/ravine-crocked situations, you may
still have to rely on conventional survey tools, or perhaps a
GPS+rangefinder system from a vantage north of the powerline, or a
mining-style relay. 
Your plan to rent (or get a try-out period) a GPS system to gage its
performance under your own situations, before you make a purchase, is a
good one.&nbsp; When you get to that point, please drop a line about the
results to shruglist.&nbsp; 
Good hunting, 
Jack Jordan 
UF-IFAS-CRS 
At 07:47 AM 10/19/2005, Tripp Corbin wrote: 
<blockquote type=3Dcite class=3Dcite cite>Holli, 
Based on my experience, which has not been with Trimble units, in order
to get reliable sub-meter locations WAAS correction is not sufficient. I
would only guarantee plus or minus 2 to 3 meters using WAAS alone. In
order to get reliable sub-meter positions in the field without post
processing, I use either Coast Guard beacons or Omnistar corrections.
Otherwise post processing is required. 
&nbsp; 
I hope this helps.=20
 
&nbsp; 
&nbsp; 
Tripp Corbin, MCP, GISP 
Associate Vice President, GIS/Mapping 
ESRI Authorized Instructor 
 
Keck &amp; Wood, Inc. 
 
<a=
 href=3D"http://www.keckwood.com/">www.keckwood.com</a> 
 
(678) 417-4013 
 
(678) 417-8785 fax 
 
&nbsp; 
Keck &amp; Wood, Inc now offers Introduction to ArcGIS/ArcView=
 training classes. Contact me for more information. 
Currently Scheduled Classes: 
Introduction to ArcGIS I - October 25-26 in Thomasville, GA (Class is=
 sponsored by the <a href=3D"http://www.swgrdc.org/planning.htm">Southwest=
 GA RDC GIS Dept.</a>) 
Introduction to ArcGIS II - November 7, 9, &amp; 10 at the <a=
 href=3D"http://shrug-gis.info/workshop05">SHRUG Workshop</a> in=
 Tallahassee, FL=20
<dl>
<dd>-----Original Message-----=20
<dd>From: shrug-l-admin@lists.dep.state.fl.us [<a=
 href=3D"mailto:shrug-l-admin@lists.dep.state.fl.us"=
 eudora=3D"autourl">mailto:shrug-l-admin@lists.dep.state.fl.us</a>] On=
 Behalf Of Holli Brandt=20
<dd>Sent: Tuesday, October 18, 2005 7:50 AM=20
<dd>To: shrug-l@lists.dep.state.fl.us=20
<dd>Subject: shrug-l: Trimble ProXRS VS Trimble GeoExplorer XT 

<dd>Good Morning Everyone -=20
<dd>Yes, I am still plugging the forum for information even though I have=
 moved.&nbsp; Still the best source for information and opinions.=20
<dd>&nbsp;=20
<dd>We are going to be completing some field=
 work in the near future and are looking into renting a GPS Unit (trying it=
 out before we buy).&nbsp; For sub-meter accuracy, the following two units=
 were recommended time and time again, the Trimble ProXRS VS Trimble=
 GeoExplorer XT.&nbsp; I am aware of the basic differences between these two=
 units, ProXRS has external antennae and differential GPS and the GeoXT has=
 internal antennae and WAAS.&nbsp; I know which way I am leaning but would=
 like to hear what any of you have to say before I commit.=20
<dd>&nbsp;=20
<dd>Any personal opinions or criticisms about=
 these units?&nbsp; Which do you suggest?&nbsp; Any other GPS unit you=
 prefer?=20
<dd>&nbsp;=20
<dd>&nbsp;=20
<dd>Thanks - Holli=20
<dd>&nbsp;=20
<dd>&nbsp;=20
<dd>Holli M. Brandt=20
<dd>Project Manager=20
<dd>EnVetCo=20
<dd>500 S. Independence Blvd=20
<dd>Suite 200=20
<dd>Virginia Beach, VA 23452=20
<dd>(757) 518-8491=20
<dd><a=
 href=3D"blocked::mailto:brandth@tesorocorp.com">brandth@tesorocorp.com</a><=
/font>=20
<dd>&nbsp;=20
</dl></blockquote></body>
 
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