Geoscience Reference
In-Depth Information
walking to find out what your average walking speed is. To determine
this, set the receiver to the page where you can determine how fast you
are moving (km/h). If you could sustain 5 km/h, each day you could
cover 120 km. You could thus walk around the Earth in 40008/120, or
333.4 days. However, traversing the ice at the poles, mountain ranges,
and the oceans would significantly slow your progress!
5. How long would it take to walk along the equatorial circumference
(in days)? At the same rate of speed that was used above, you could
walk around the Equator in 385.4 days. Here, mountains in Ecuador,
Kenya, and Indonesia would slow your progress, and once again you
would have that pesky problem of traversing the oceans.
6. How long would it take for you to walk along the circumference of
your line of latitude in Table 2.2 (in days)? At 40 degrees north lati-
tude, the circumference is 30,656.92 km. Therefore, it would require
255.5 days at 120 km/day.
2.3.4 Determining the mass and volume of the Earth using Table 2.3
With a GPS, you can also determine the mass and volume of the Earth. Follow
steps a through f in Table 2.3 .
2.4 Measuring positions on the Earth surface, and fractions
Most of us studied fractions from primary school to university level and use
them in our everyday lives. However, when engaged in field work, it is impor-
tant to feel comfortable with such matters so that one can devote full attention
to what is going on in the field and need not have to stop and consider frac-
tional conversions and transformations. Thus, we offer a quick review of frac-
tions emphasizing conversion from degree/minute format to decimal degrees
and the addition of fractions with different denominators. We illustrate the
concepts through worked examples.
For example, consider the conversion of 42 degrees, 31 minutes, 47 sec-
onds, to decimal degrees. This entity can be written in fractional form as
42 + 31/60 + 47/3600. Use a calculator to evaluate the answer. Where did the
value of 3600 come from? Consider the standard clock. It is in base 60, with
60 seconds creating one minute, and 60 minutes creating one hour. Similarly,
measurements on the Earth are in degrees, minutes, and seconds (DMS), also
in base 60, but with degrees, minutes, and seconds measured as distances
instead of time units. So, here, 3600 is 60 squared, required because 60 sec-
onds create one minute, and 60 minutes create one degree. So, the answer is
simply (approximately) 42 + 0.5167 + 0.013056 = 42.529756.
Now, reverse the process: Convert 42.53 to degrees, minutes, and seconds.
Seconds is the finest unit. There are 3600 seconds in a degree because there are
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