brown & sharpe Global 121510, Руководство пользователя

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Introduction to CMM
Global User Manual
10-9
Intro. to CMM
An Explanation of Datum
A datum is a location. We use datum’s as guides to tell others
where we are or as directions on how to get to places. On the
map shown the Ritz Hotel is a datum. So are streets, the train
station, the museum, and the restaurant. Thus, by using an
origin, datum’s, directions and distances people have all the
information they need to get from one location to another.
For example, to get from the train station (origin) to the restau-
rant, you walk 2 blocks north on Elm Street (datum), take a
right, and walk 2 blocks east on Maple (datum).
Figure 14 Map Datums
Ma
ple
A
1
2
3
4
5
B
C
D
E
Birc
h
Ch
es
tnu
t
Sycamore
Elm
Oak
Ritz Hotel (Datum)
Restaurant (Datum)
Train Station (Datum)
Museum (Datum)
Figure 6