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I received an inquiry from Laughlin AFB in Del Rio, TX last week about their upcoming Half Marathon and 5K. The courses had been mapped out by the base Civil Engineers use GSI (Geographic Information System). Their question was - does this count as measuring? I gave them the name of the nearest measurer to DEl Rio.
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GIS is new to me. I expect the raw data is the same as what we see on Google Earth, and I'd expect the same level of accuracy.

I did a search and got:

GIS Mapping

I would be reluctant to accept this as equal to a competently-done bike measurement. One drawback is that the certifier would be presented with a take-it-or-leave-it pile of data.

There may be information relating to the accuracy of the method, but until such is presented and made understandable and credible, I do not believe we should accept it for course certification.
I have used GIS a little bit over the years. But I see no way it would be able to produce the type of accuracy we get with our current method. There's nothing like being on the ground. Some problems: (1) the image one is working with could be old, (2) the image has to be stretched to match control points on the ground and this procedure could be very different for different GID systems, (3) (Pete's point) how would the course be certified?

I totally agree with Alan. I use GIS mapping on a daily basis, and would not support its use in course certification.

To properly measure around curves, you would have to drop a measurement (track) point every 3 feet, or so. Unless you have a high-res image to work with, this is not feasible. Also, if the winding course passes under trees (as a park in Kansas has, which I measured), you cannot see the road, let alone the edges of the road.

No, GIS cannot be used for certification. I could compile examples of its inadequateness for the task, but that would take more time than it is worth. Suffice it to say that I can plot a course for surveyors to follow, and they get a different length for the road than what the software gave me.

Not to mention the elevation changes in a course, which GIS is taking from a database with partial data. An undulating road would not measure accurately. Cross a dam, and most GIS takes the elevation from the original countour, not the flat dam road (had that situation, also).

Nope. Can't use GIS for certs. Fine for pre-measure, though.

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