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August 4th, 2008
Cadastral Expert Improves Business with Low-Cost GPS

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PR – Alessandro
Prudenzi is considered by many to be one of the pre-eminent cadastral experts in
the Brescia region of Lombardy. He’s proud of that reputation and does all he
can to retain the respect of his colleagues and clients.  Ultimately, that means working to the
highest standards of quality and accuracy.


An architect
by training, Prudenzi served in the Brescia Office of Cadastre for ten years,
then, fifteen years ago, he opened his own independent office to perform
appraisals and verifications of local real estate property and technical
consulting to the Court of Brescia. 
Because land survey is just one aspect of his multi-faceted practice,
Prudenzi had until recently relied solely on a total station for land survey
work. He knew, though, that there’s no one tool for every job; in difficult
terrain, GPS would be a better solution. But GPS has been cost-prohibitive,
particularly for the limited use Prudenzi expected to give it. He knew too that
GPS products have been changing rapidly. 
GPS would make sense if he found a high-accuracy system that would
amortize quickly even with limited use. 


He found an
ideal solution after carefully researching the available information, consulting
numerous colleagues, and testing many different GPS brands and models for
accuracy, ease of use and cost. 
With the study complete, Prudenzi found that Magellan, one of the
fasting-growing GPS brands in the world, offered the best solution with its
ProMark3 RTK.  Its low cost, high
accuracy, simplicity of operation, and versatility proved superior. Prudenzi
said that Giorgio Viaggi, of Guido Veronesi SRL, the Italian distributor for the
Magellan ProMark3, provided excellent assistance in helping to select the
ProMark3 RTK.



reports that in many tests conducted in his backyard on different days, the
ProMark3 RTK consistently outperformed Magellan’s own published accuracy
standards. For example, he says, ”In static mode using a free reference network,
Spidernet, with its reference stations from 90 KM to 130 KM distant, the same
points showed a variation from 0.02 to 0.04 m, against a predictable and
acceptable datum, which Magellan publishes, of 0.095 to 0.125 m (0.005m +
1ppm).  The true values are
decidedly better than those expected.”


And in
different RTK tests he conducted, he says, “using previously calculated points,
the verifiable error is always in my experience less than 0.01



processing: convenience and low cost

Prudenzi’s view, a decisive advantage of the ProMark3 RTK is its ability to
simultaneously collect raw data during RTK sessions.  “I want to underline,” he says, “that
Magellan has great post-processing software, GNSS solutions office software, and
it’s free. In my experience, surveyors can be frightened by the cost of
post-processing software and so they do surveys only in RTK. When I’m in RTK
mode, I now always collect for 15 seconds on every point to gather the raw data
that later allows me to easily reduce my error down to 0.001 to 0.003m.  In this way, the ProMark3 RTK delivers a
level of accuracy the equal of instruments costing more than twice as much.” He
adds, “It is very simple to both record data in RTK mode together with raw
data.  The raw data is then easily
used in the GNSS solutions software to achieve millimeter level accuracy, all
with a low-cost L1 unit.”


base + rover

particularly likes the ProMark3 RTK’s base plus rover system, which is
all-inclusive together with a license-free plug and play radio.  While much of Lombardy has good VRS coverage, he often works in zones
with limited coverage, one reason he particularly likes the base plus rover
freedom offered by the ProMark3 RTK.


notes that many surveyors, because of the high cost of GPS system and to hold
costs down, will purchase only a rover and use differential corrections
broadcast from nets in their area. The problem is that in too many areas
differential corrections are not available and even when they are, the virtual
reference station will sometimes be some distance away.  A virtual station 4 km distant, he
points out, will have an error of almost 4 mm.  But with the ProMark3 RTK, its low cost
includes a base station and rover, at a cost equivalent to what another brand’s
rover alone costs.  “When I collect
in RTK using the base station and simultaneously collect raw data, I can achieve
a precision up to ten times better than the rover only with differential



always uses the ProMark3 RTK in difficult physical conditions, such as demanding
terrain and significant vegetation. 
In these conditions a job that would take two days with a total station
takes but a couple of hours with the ProMark3 RTK.  Importantly, the relatively low cost of
the ProMark3 RTK means that even in Prudenzi’s limited field survey work, the
cost is quickly amortized.


cadastral law requires the use of three reference points to locate a house.  Therefore, a house might require a
minimum of more than a dozen points to be measured. And those points all need to
be right on.  Even though the
ProMark3 RTK is half the cost of competitive brands offering similar results,
its accuracy is so impressive that Prudenzi now uses the unit for almost half
his land survey jobs. 


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