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Chapter 2 Where in the Geospatial World Are You?
GCS and UTM are completely different systems,
but there are utilities to make conversion from one
system to another simple and easy. One of these is
available at http://www.cellspark.com/UTM.html.
This Web resource is used to convert from GCS to
UTM or vice versa. You can specify your datum (reference ellipsoid), and then enter the latitude and
longitude coordinates of a location (in either DD
or DMS) and the utility will calculate the location’s
UTM coordinates. It can also calculate the latitude
and longitude values when given UTM coordinates.
The first step is to obtain GCS coordinates
of places before figuring out what their UTM
equivalents are. A good source of coordinates can be
found at http://lat-long.com. This Website allows
you to input the name of an object (for instance,
use the Empire State Building) and the state (New
York) or county and it will return the lat/long (in both
DD and DMS) for that place. Copy those coordinates
into the UTM converter (use the WGS84 ellipsoid) to
determine the UTM coordinates of the Empire State
Building. Use the two Websites in conjunction with
each other to determine the UTM coordinates of
prominent locations around your area (public libraries, city hall, or your school).
Hands-on Application 2.3
Converting from Latitude/Longitude to UTM
Like UTM, SPCS requires you to specify a zone, an easting, and a northing in
addition to the state the measurements are being made in.
SPCS divides the United States into a series of zones. Unlike UTM Zones,
which follow lines of longitude, SPCS zones are formed by following state
or county boundaries. A state is often divided into multiple zones—for example, Ohio has two zones: Ohio-North and Ohio-South. Nevada has three
zones: Nevada-West, Nevada-Central, and Nevada-East. Texas has five zones,
California has six zones, while all of Montana is represented by a single zone
(Figure 2.8). To determine the coordinates for a point in SPCS, you must first
know which state the point is in and then identify the zone in that state. For
example, to map data from Miami, the state would be Florida and the zone
would be Florida-East, while Cleveland would be in the state of Ohio and in
the Ohio-North zone.
The next step is to determine the northing and easting. Like UTM, both
of these are measured north and east from a pre-determined baseline and
meridian, but in SPCS, measurements are made in feet (using the NAD27
datum) or in feet or meters (using the NAD83 datum). Each of the SPCS
Zones has its own baseline and its own principal meridian. Two projected versions of SPCS are used—the Transverse Mercator version, which is usually
used for states that have a north-south orientation (such as Indiana), and the
Lambert Conformal Conic version, which is usually used for states that have
a more east-west orientation (such as Ohio). Depending on the version used,
the zones’ baselines and meridians are positioned differently.
Baselines are placed a distance under the zone’s southern border and
measured north from there (to ensure all positive values). In the NAD27
SPCS zone one of the
divisions of the United
States set up by the
SPCS.
Chapter 2 Where in the Geospatial World Are You?
GCS and UTM are completely different systems,
but there are utilities to make conversion from one
system to another simple and easy. One of these is
available at http://www.cellspark.com/UTM.html.
This Web resource is used to convert from GCS to
UTM or vice versa. You can specify your datum (reference ellipsoid), and then enter the latitude and
longitude coordinates of a location (in either DD
or DMS) and the utility will calculate the location’s
UTM coordinates. It can also calculate the latitude
and longitude values when given UTM coordinates.
The first step is to obtain GCS coordinates
of places before figuring out what their UTM
equivalents are. A good source of coordinates can be
found at http://lat-long.com. This Website allows
you to input the name of an object (for instance,
use the Empire State Building) and the state (New
York) or county and it will return the lat/long (in both
DD and DMS) for that place. Copy those coordinates
into the UTM converter (use the WGS84 ellipsoid) to
determine the UTM coordinates of the Empire State
Building. Use the two Websites in conjunction with
each other to determine the UTM coordinates of
prominent locations around your area (public libraries, city hall, or your school).
Hands-on Application 2.3
Converting from Latitude/Longitude to UTM
Like UTM, SPCS requires you to specify a zone, an easting, and a northing in
addition to the state the measurements are being made in.
SPCS divides the United States into a series of zones. Unlike UTM Zones,
which follow lines of longitude, SPCS zones are formed by following state
or county boundaries. A state is often divided into multiple zones—for example, Ohio has two zones: Ohio-North and Ohio-South. Nevada has three
zones: Nevada-West, Nevada-Central, and Nevada-East. Texas has five zones,
California has six zones, while all of Montana is represented by a single zone
(Figure 2.8). To determine the coordinates for a point in SPCS, you must first
know which state the point is in and then identify the zone in that state. For
example, to map data from Miami, the state would be Florida and the zone
would be Florida-East, while Cleveland would be in the state of Ohio and in
the Ohio-North zone.
The next step is to determine the northing and easting. Like UTM, both
of these are measured north and east from a pre-determined baseline and
meridian, but in SPCS, measurements are made in feet (using the NAD27
datum) or in feet or meters (using the NAD83 datum). Each of the SPCS
Zones has its own baseline and its own principal meridian. Two projected versions of SPCS are used—the Transverse Mercator version, which is usually
used for states that have a north-south orientation (such as Indiana), and the
Lambert Conformal Conic version, which is usually used for states that have
a more east-west orientation (such as Ohio). Depending on the version used,
the zones’ baselines and meridians are positioned differently.
Baselines are placed a distance under the zone’s southern border and
measured north from there (to ensure all positive values). In the NAD27
SPCS zone one of the
divisions of the United
States set up by the
SPCS.