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ctxguide
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PostPosted: Tue Jul 29, 2008 1:02 am    Post subject: Mapomania Reply with quote

Read below about my revelations while working toward completing the National Geographic Maps NavPro exam.
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ctxguide
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Joined: 01 Jan 1970
Posts: 2422

PostPosted: Tue Jul 29, 2008 1:04 am    Post subject: Reply with quote

I spent the last several weeks working toward completing my National Geographic Maps NavPro exam and in the process have learned quite a few new things.

First of all, I remember while backpacking in the mountains of North Carolina how concerened we were with the reliability of our GPS unit. At that time (1998), the US government tampered with the satellite signals so that civilian GPS units could not be nearly as accurate or reliable as the government's. This was called selective availability. Because of this, us old timers working with GPS units for the last ten years or more may just assume that we have to be careful of the governments tampering. I am releived to say that selective availability was discontinued in 2000 and the signals are no longer tampered with intentionally.

The other shocker was how much that crazy magnetic north moves around. I knew that it moved, but it can actually move by as much as 80km in one day! It kind of oscilates on a daily basis, which is why it can move such a great distance within 24 hours. It also migrates as much as 40km northwest each year. This may not seem like such a big deal, but whenever calculating magnetic declination with your compass, be careful of maps greater than two years old. Old maps may have significant magnetic declination discrempancies, so user beware. A handy magnetic declination calculator can be found at http://www.ngdc.noaa.gov/geomagmodels/Declination.jsp .

Besides the above concepts, I also had to define the following terms: rastor & vector maps, teslin, NAD 27 CONUS, UTM, WAAS, DEM, agonic line, isogonic line, Universal Polar Stereographic, planimetric, hypsometric, DRG, bathymetry, great circle, bearing, and heading (among many oethers). This was very much a technical exam.

If you would like to see if you can pass the exam, go to http://www.topo.com/forums/34/topics/863 and click on the link from the first posting. If you pass, you receive 25 map credits toward topo maps for the free TOPO! Explorer application as well as a NavPro hat, patch, and stickers (I was hoping for a coloring book). If you get them all correct, you get the equivalent of a TOPO! State Series in map credits! This is easier said than done. I knew quite a bit about maps and navigation to begin with, so I was gunning for the 100%. Even so, I still missed quite a few questions.
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