COMMUNITY MAPPING: Converting Geographic Coordinates Manually
ASK
Do you know that there is more than one way to record latitude and longitude? Why is it important to convert all
coordinates into one format and how is it done?
In this section, you will learn three ways geographic coordinates (latitude and longitude) are formatted. You will also
learn how to use a formula to convert the coordinates into one consistent format.
INVESTIGATE
It is important to understand the different ways geographic coordinates are recorded because if they are not in the same
format it can get very confusing. Plus if you are creating a layered map, you cannot layer coordinates onto your map
unless they are the same format. In other words, waypoints will not show up on your map until you convert them all
into the same format.
RECORDING LATITUDE AND LONGITUDE
There are three ways to record latitude and longitude.
1. Decimal Degrees (DD) places latitude and longitude coordinates in decimal fractions. This method is commonly
used with GPS, GIS, and online map applications.
2. Decimal Minutes (DM) places latitude and longitude coordinates in decimal minutes.
3. Degrees Minutes Seconds (DMS) places latitude and longitude coordinates in degrees, minutes, and seconds.
EXAMPLE
All of the formats below refer to the same location. The latitude and longitude are represented differently in different
formats.
The State 4H Office
1902 Fox Drive
Champaign, IL. 61820
Normal GPS Coordinates (WGS84 Datum)
DD
DM
DMS
40.09254 -88.24866
N 40° 05.552 W 088° 14.919
N 40° 5’ 33.1476” W 88° 14’ 55.1652”
DD (Decimal Degree) = N 40.09254, W -88.24866
DM Decimal Minutes = N 40° 5.552, W 088° 14.919
DMS (Degrees Minutes Seconds)= N 40° 5’ 33.1476” W 088° 14’ 55.1652”
(lat) 40 degrees 5 minutes 33.147 seconds
(lon) -88 degrees 14 minutes 55.1652 seconds
CONVERTING COORDINATES
Converting your waypoint data from Degrees Minutes Seconds (DMS) to Decimal Degree (DD) format (or vice versa) is
easy and can be done automatically on the Internet or it may be converted manually with this formula:
(D + M/60 + S/3600) = DD
CREATE
Let’s say you live in the city of Springfield, the state capitol of Illinois. Your club’s members have identified and divided
up local places of interest and have gathered their coordinates. All coordinates are in the Decimal Degree (DD)
format except for the Abraham Lincoln Presidential Museum. That person’s GPS receiver was set to Decimal Minute
DM conversions, and therefore that waypoint does not show up on your map. You need to convert the latitude and
longitude coordinates from DM to DD.
Abraham Lincoln Presidential Museum
212 N. Sixth Street
Springfield, IL 62701
DM coordinates
Latitude: 39º. 48.103 Longitude: 089º. 38.873
D
D
M
M
Use the formula above to convert these coordinates from DM to DD. Remember, if you do not have a coordinate to put
in the formula then zero is used.
Click for the correct answer: DD = (lat) 39.80172 (lon) -89.64788
DISCUSS
• When is it necessary to convert geographic coordinates into the same format?
• Did you find the manual formula easy to use? Explain.
REFLECT
• How can your new conversion skills help you now and in the future?
Developed by Dr. Lisa Bouillion Diaz, Barb Roberts, Terri Myers, Dr. Nama Budathoki, Wilbon Anthony, Susan Hayden, and
Dawn Waller. University of Illinois Extension, 2011. College of Agricultural, Consumer & Environmental Sciences/State/
County/Local Groups/USDA cooperating. University of Illinois Extension provides equal opportunities in programs and
employment. http://web.extension.illinois.edu/4hmapmakers/