Latitude is measured in degrees north when in the northern hemisphere and degrees south when in the southern hemisphere. [2] X Research source
180 degrees longitude is known as the international dateline. [4] X Research source Longitude is given as degrees east when in the eastern hemisphere and west when in the western hemisphere. [5] X Research source
Online topographic maps express longitude and latitude decimal degrees in degrees, minutes and seconds. Each degree equals 60 minutes, while each minute equals 60 seconds. The comparison to time allows for easier subdivision. [7] X Research source
Remember how to convert time in order understand a map using decimal degrees as degrees, minutes, and seconds[9] X Research source : 15 seconds = one quarter of a minute = 0. 25 minutes 30 seconds = half a minute = 0. 5 minutes 45 seconds = three quarters of a minute = 0. 75 minutes
Depending on what you’re trying to locate, make sure you’re using a map with an appropriate scale. If you want to find how far a state is from your own, you would want to use a map of the United States rather than one of the world.
Your map should have the lines of latitude and longitude forming a grid and dividing it into cross sections. A map ruler is easy to use and can be purchased at an outdoor supply store or online. Make sure that your map ruler corresponds to your USGS 1:24,000 scale map series. [12] X Research source Measure latitude first. The lines of latitude will be north and south parallels to your location. Place the zero end of your map ruler on the southern parallel. The next parallel to the north should be touched by the 2 ½ minute end. One edge of the ruler will be marked in minutes and seconds while the other edge is decimal minutes. Make sure to use the correct edge that corresponds to the coordinate format of your map. Slide the ruler to the right – or to the west – until it touches your location. Mark how much distance is between the southern parallel to your location. Add this to the latitude of the southern parallel to get the latitude of your location. [13] X Research source To measure the longitude you must place the ruler diagonally on the west and east meridians with the ends of the 2 ½ minute ruler touching both meridians. The lines of longitude on your map will be the east and west meridians of your location. You must measure diagonally because if you measure horizontally, the ruler extends past the grid because the meridians of longitude grow closer as they move from the equator. Move the ruler vertically until you find your location making sure to keep both ends of the ruler on the meridians at a diagonal. Record where your location is – in minutes and seconds – west of the eastern meridian. To find the the longitude of your location, add your measurement to the longitude of the eastern meridian. [14] X Research source
When writing down your coordinates, you may format latitude and longitude in three different ways[15] X Research source : Degrees (d. d°) - 49. 5000°, -123. 5000° Minutes (d°m. m’) - 49°30. 0’, -123°30. 0’ Seconds (d°m’s) - 49°30'00"N, 123°30'00"W When dealing with latitude and longitude, the North - South and East - West designators are removed and replaced with negative values for points south of the equator. [16] X Research source
Use a plumb line to ensure that the stick is vertical. [18] X Research source A plumb line is exactly as it sounds: a line with any type of plumb attached to it. Gravity will ensure that the plumb creates a vertical line.
Center a protractor at the pivot point. Suspend the plumb line also from this pivot point. [20] X Research source
The measurements are not completely accurate, other than spring and autumn equinox, because of the way the Earth is tilted as it orbits around the sun. [24] X Research source While there are complex tables that give you the correct factor to determine your exact latitude and longitude on any given day, accurately estimate based on the date relative to the spring and autumn equinox. For example, if you are measuring at the start of May, which is half-way between the spring – when the sun is directly above the equator – and summer equinox – when the sun is above 23. 45 degrees north of the Equator, you would just need to add half of 23. 45 degrees – 11. 73 – to your measurement. [25] X Research source
