Question 1

What does geodesy have to do with GIS?

Every GIS professional should be able to use the following concepts proficiently:

• Geoid
• Ellipsoid
• Latitude
• Longitude
• Datum

In specific, practicing in North America in the current era, these are implemented as:

• North American Datum of 1927
• North American Datum of 1983
• World Geodetic System 1984
• Clarke's Ellipsoid of 1866
• High Precision GPS Network (HPGN) (around Puget Sound, anyway)

1. Determine the "datum shift" from some prominent place in your life (home town, current residence, etc.). Write a paragraph explaining the phenomenon that your mother (or some significant non-GIS person) might understand.
2. Crusty operates the County CAD system for Benighted County. Give Crusty a good reason why to change his NAD27 data into NAD 83.
3. Determine the "deflection of the vertical" for some locations of interest to you (Hint these values are rather large around the Cascade range.) Explain the consequences of this phenomenon to users of traditional surveying, give the magnitude of the effect.
4. Take a look at some of the Global Grids literature (Lukatela's Hipparchus, Dutton's QTM, etc.). Present an argument to your boss (obviously design the project accordingly) to argue why to use something more exotic than planar coordinates or latitude longitude...
5. If the aliens abduct you and deposit you on a desert island with the most minimal of equipment (say, for purposes of argument, a pole 1 meter long and a Rolex watch), how long would it take you to figure out if you were a) still on the planet Earth? b) what location you were in if it is the Earth? What procedures would you have to use to determine these results? What other equipment would help you determine this more quickly (short of a pocket GPS- that is cheating! Aliens take all GPS receivers, since the silicon chips provide special nutrients for them...)

Your answers shouldn't be much longer than one page... The documentation of the NADCON software should help, as well as the Geoid96 project pages at National Geodetic Survey. See links from Lecture 3.