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Think about this—you’re at the mall and your cell phone rings. It’s a friend calling you with a really basic question: “Where are you?” For such a simple question, there’s really a wide variety of answers. You could say “I’m at the mall,”
which gives the other person some basic location information, but only providing they know where the mall is. If they’re calling from out of town and unfamiliar with the location of the mall, what you’ve told them is useless for them to
know where you are. If you tell them “I’m in Columbus,” then they have another
type of information, but Columbus is a big city, and they still don’t know where
you are in the city. You could give them the name of the cross streets by the mall,
the address of the mall, or the name of the store you’re in at the mall, and even
though all of the above contain different levels of information, your friend still
won’t have the information needed to know precisely where you are.
For instance, the answer of “I’m at the mall” effectively conveys your
location only if the person you’re talking to has some sort of knowledge of
the mall’s location. If she has a reference like “the mall’s on the north side of
town” or “the mall is just off exit 5 on the freeway,” then she has some idea
of your location. For the location information to make sense, she needs to
have something (perhaps a map of the city you’re in) to reference the data to.
If you need specific information about your exact location, you’d have to be
much more specific than saying you’re at the mall. For example, in the case
of a medical emergency, Emergency Medical Technicians (EMTs) would need
to know your exact location (they couldn’t afford to waste time searching the
entire mall to find you). In this particular case, you would need to provide
precise location information so that the EMTs would be able to find you, no
matter where you are.
Geospatial technology works the same way. First, since it deals with
geospatial data (that is linked to non-spatial data), there has to be a way of
Where in the Geospatial
World Are You?
Locations in a Digital World, Position Measurements, Datums,
Coordinate Systems, GCS, Map Projections, UTM, and SPCS
2
Think about this—you’re at the mall and your cell phone rings. It’s a friend calling you with a really basic question: “Where are you?” For such a simple question, there’s really a wide variety of answers. You could say “I’m at the mall,”
which gives the other person some basic location information, but only providing they know where the mall is. If they’re calling from out of town and unfamiliar with the location of the mall, what you’ve told them is useless for them to
know where you are. If you tell them “I’m in Columbus,” then they have another
type of information, but Columbus is a big city, and they still don’t know where
you are in the city. You could give them the name of the cross streets by the mall,
the address of the mall, or the name of the store you’re in at the mall, and even
though all of the above contain different levels of information, your friend still
won’t have the information needed to know precisely where you are.
For instance, the answer of “I’m at the mall” effectively conveys your
location only if the person you’re talking to has some sort of knowledge of
the mall’s location. If she has a reference like “the mall’s on the north side of
town” or “the mall is just off exit 5 on the freeway,” then she has some idea
of your location. For the location information to make sense, she needs to
have something (perhaps a map of the city you’re in) to reference the data to.
If you need specific information about your exact location, you’d have to be
much more specific than saying you’re at the mall. For example, in the case
of a medical emergency, Emergency Medical Technicians (EMTs) would need
to know your exact location (they couldn’t afford to waste time searching the
entire mall to find you). In this particular case, you would need to provide
precise location information so that the EMTs would be able to find you, no
matter where you are.
Geospatial technology works the same way. First, since it deals with
geospatial data (that is linked to non-spatial data), there has to be a way of
Where in the Geospatial
World Are You?
Locations in a Digital World, Position Measurements, Datums,
Coordinate Systems, GCS, Map Projections, UTM, and SPCS
2