Latitude and Longitude
Introduction to Chart Navigation for
“THE CHARLESTON HARBOR CIVIL WAR BATTLE MAP”
There is general acceptance that the available navigational information and data used to develop this graphical chart, to position shipwrecks and general battle areas is far more accurately presented than the navigational means available to the subject matter of the chart.
All locations on Planet Earth can be described by two numbers--its latitude and its longitude. If a ship's captain wants to specify a position on a map, these are the "coordinates" they would use. Knowledge of the harbor and it’s history with its unchanging landmarks and recent verifications of facts assisted by the availability of information on the internet made this map possible.
List of shipwrecks and obstructions in Charleston Harbor in PDF format
Latitude: Measurement of distance in degrees north or south of the Equator; from the Latin latus, meaning "wide".
Longitude : Measurement of distance in degrees east or west of the prime meridian; from the Latin longus, meaning "length".
How To Convert a Decimal to Sexagesimal
You'll often find degrees given in decimal degrees (121.135°) instead of the more common degrees, minutes, and seconds (121°8'6"). However, it's easy to convert from a decimal to the sexagesimal system.
Here's How:
longitude and latitudes have been divided into degrees, minutes (') and seconds ("). There are 60 minutes in each degree. Each minute is divided into 60 seconds. Seconds can be further divided into tenths, hundredths, or even thousandths.
Latitude Longitude Conversion a. The number is positive so its a NORTH latitude. So 32.71909722° is 32.71909722° N. |
e. Multiply the remaining 0.145832' by 60 to get the number of seconds: 0.145832 x 60 = 8.74992 seconds (8.74992"). |
b. Break up the 32.71909722° into 32° + 0.
71909722°. So the number of whole degrees |
f. Round off: 8.74992 seconds becomes 08.75 seconds. |
c. Multiply the remaining 0. 71909722° by 60 to get the number of minutes: 0. 71909722 x 60 = 43.145832 minutes (43.145832 '). |
g. So, the latitude is 32° 43' 08.75" NORTH latitude. |
d. Break up the 43.145832 ' into 43' + 0.145832 '. So the number of whole minutes is 43'. |
h. So the final answer for the latitude |
Symbols: ° Degrees ' Minutes "Seconds
Degrees, Minutes and Seconds
DDD° MM' SS.S"
32° 43' 08.75"N
This is the most common format used to mark maps. It's also the most
cumbersome to work with. It's a lot like telling time…
There are sixty seconds in a minute (60" = 1') and
There are sixty minutes in a degree (60' = 1°).
The
Charleston Harbor Civil War Battle map is taken from the format used
by Navigational charts. The minutes are divided into tenths of a minute giving
each mark a value of 6 seconds.
Keeping in mind a few easy conversions between seconds and decimal minutes will
help when working with maps that use degrees, minutes and seconds.
15 seconds is one quarter of a minute or 0.25 minutes
30 seconds is one half of a minute or 0.5 minutes
45 seconds is three quarters of a minute or 0.75 minutes
Degrees and Decimal Minutes
DDD° MM.MMM'
32° 18.385' N 122° 36.875' W
This is the format most commonly used when working with electronic navigation equipment.
Decimal Degrees the format most computer based mapping systems display
DDD.DDDDD°
32.30642° N 122.61458° W
or +32.30642, -122.61458
The basic unit of latitude and longitude is the degree and subdivisions of a degree. NOAA will also use a decimal point, such as 32.789°N referred to as decimal degrees on their Chart of Obstructions. Decimal degrees are an option on Global Position Systems (GPS) or with online topographic maps, but decimal degrees are not used on printed maps. On these topographic maps the latitude and longitude units are expressed in degrees, minutes, and seconds. Each degree is subdivided into 60 minutes('). Each minute is divided into 60 seconds(''). The Seconds are tick marked and divide the minutes into 10 parts giving each mark a value of 6 seconds (“)
List of shipwrecks and obstructions in Charleston Harbor in PDF format
www.hunleystore.com to purchase map. |