Friday, 10 August 2012

GPS Tip - Position Averaging

Today's GPS tip is using position averaging.

Most mobile GIS software defaults to using one single GPS
position to define the XY of a point feature. That's quick but it
may not be very accurate.

Say that the accuracy of your GPS unit is 3 meters. You can imagine
an imaginary 'accuracy circle' with a radius of 3 meters extending
out from your GPS position.

When you start logging GPS data, the positions come in at whatever
frequency you've specified - maybe one position a second.

The majority of those positions will fall within the imaginary
accuracy circle - some of them closer to your actual location,
others farther out along the perimeter of the circle.  Some will
even fall outside of the circle entirely.

If only one GPS position is used to define the feature's coordinate,
it may dead-on at the actual XY, but it might just as easily be
outside of the circle - a difference of 3 meters in this example.

Position averaging allows you to collect several GPS positions
instead of just one.  Most will be in the circle, some will not -
but all get averaged together.

That averaged XY becomes the final coordinate of the point feature
and it's a very simple way to improve the accuracy of point data.

Happy Mapping!


Tuesday, 10 July 2012

GIS as a key Infrastructural component with immense value and benefits for Surveyors as well as for Spatial Planners and Scientists

GIS as a key infrastructural  component with immense value and  benefits for surveyors as well as for spatial planners and scientists.

What benefit do we have by using GIS? A column written by Jeff Thurston (Director Integral GIS, Inc.) about “Determining Benefits and Advantages of GI” in GeoInformatics (October/November 2002) provides a partial answer to this question. “GI has emerged, “ wrote Thurston, “from the lone individual in the corner office working away on some unknown project and using some unknown technology, and this individual was very hard to communicate with during coffee breaks. Those GI people seemed to speak a different language. Every once in a while a person would produce a colorful and useful map. It looked simple enough, and over time more and more people kept asking for maps. Then they wanted to compare things spatially. Next thing we knew there was a GPS and some satellite data in the organization. Then more and more people wanted to do different things with the data and the organization hired more of these people ...” [Thurston, 2002]. 
The text continues with the narrator questioning his fictional boss about the purpose and the benefit of this technology he does not fully understand:
“It surprised me when the boss said we are providing GIS data for business, entertainment, and environmental applications, sociological, population and even for research studies for other organizations amongst others” [Thurston, 2002].
Last but not the least, Thurston leaves us with the awareness that the information contained in GI-datasets such as cadastral and legal land registers, utility registers, and map databases is a key infrastructural component carrying immense (capital) value [Falk and Oliv, 2003]. But it is not only the value of the datasets; we also profit from the ability of GI-systems to analyze, compare, and combine them in their complex spatial context. By using these systems we can find answers for spatial questions that we would otherwise be hard pressed to obtain or be unable to provide. Thus it should not come as
a surprise that since Roger Tomlinson coined the term “Geographic Information System” for the Government of Canada in the early 1960s (Coppock and Rhind, 1991), the development of GI-systems and applications has made giant steps forward. Without realizing it, GIS has become a commodity without which our everyday life would be hard to imagine. But—and this is my question— do we already know and use all possibilities and advantages of GIS in our profession and for broadening the scope of our activities? Let’s
not forget that it was FIG and the German DVW president who sponsored the first international conference on Land Information Systems (these days discussed under the general term GIS) in
Germany in 1978. I attended the conference, but the response of other practitioners and academics was close to zero! It took almost 15 years for GIS to became a hot issue among European surveyors and universities (Schilcher, 2001).

This is a clip from  —opening address by univ. prof. dr. ing. holger magel, president, FIG. 
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