[GeoStL] Re: what is this?

That is a surveyor's nail in asphaltic concrete at the Harrisburg airport. 
Those types of surveyors marks are placed in areas where a traditional flag on 
a stick won't work, i.e., roads, parking lots, runways and taxiways, or where a 
more permanent marker is needed. The sketch on the notebook page is the 
surveyor's notes to relocate that particular nail. In this case, where NASA is 
performing some kind of high-altitude topographic mapping, these points serve 
as ground control points to tie the maps into. I notice that the one on the 
Columbia, MO, airport is an "X" chiseled into a concrete curb.
http://aol.wff.nasa.gov/aoltm/gps_sites/colum.html  
Locating these would be like hunting benchmarks. Unfortunately, most of these 
marks at airports would be in areas not generally accessible to the public 
these days.
If you back up the address to http://aol.wff.nasa.gov/aoltm you will get a 
brief explanation of how these gps waypoints are used.

Pam E. Tribble 157  


----- Original Message -----
From: Jen Guyer
Sent: Friday, October 25, 2002 8:57 PM
To: geocaching@xxxxxxxxxxxxx
Subject: [GeoStL] what is this?


http://aol.wff.nasa.gov/aoltm/gps_sites/capcity.html  

I was doing a search of New Cumberland, Penn and found this. The New Cumberland 
GPS site. And of course anything GPS catches my eye. But what is it?

Jen

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