Ethnobotanists can now record the exact location on the planet Earth a plant was found using a Global Positioning Satellite (GPS) system receiver. A GPS unit can mark the exact latitude and longitude at which a plant can be found. This not only records the location of the plant accurately, but also provides a way for future researchers to return to that exact location.
Using a GPS system requires knowing latitude and longitude. Longitude here in the FSM is measured in degrees (°) and minutes (') East of Greenwich, England. On the far side of the planet Earth, halfway around from Greenwich, is 180° degrees East, this is also 180 West. The International Date Line roughly follows the 180° degree East/West line of longitude. There are 60 minutes in one degree.
Latitude is measured in degrees North (or South) of the equator. The equator is 0 degrees latitude. The North pole is 90° degrees North Latitude, the south pole is 90 degrees South latitude.
The LRC on our campus is located at N 06°54.542', E 158°09.573'. That is read as, "Six degrees and fifty-four decimal five four two minutes North latitude, one hundred fifty-eight decimal five seven three minutes East longitude."
To provide an idea of how much these numbers change as we move on Pohnpei, the Spanish in Kolonia is N 06°57.994', E 158°12.695'. Spanish wall is only 3.452 minutes North of the LRC and 3.122 minutes East of the LRC. This 4.654 minutes Northeast "as the bird flies" using Pythagoras theorem. The straight line distance is about 8.919 km, so one minute is 1.916 km - just a little over a mile and a small amount less than 2 km.
High above the planet Earth, up in low Earth orbit, are roughly thirty satellites that a GPS receiver can contact to determine the location of the receiver anywhere on the planet Earth. Some receivers also report one's elevation above sea level as well as the latitude and longitude.
The unit we are using in class, a Garmin™ Foretrex 201® can communicate with up to 12 satellites at one time. The number of satellites and their signal strength is displayed on a satellite screen. Garmin refers to each screen as a "page." A button on the unit marked "page" allows one to change pages.
The buttons from left to right are power, goto, page, enter/mark, scroll down, and scroll up:
Because a GPS receiver knows its exact location on the surface of the planet, these units are also used to help one navigate. Most units do more than report location in latitude and longitude, they also provide information on where you have been (breadcrumb trail or track) and which way (bearing) you need to go to get to a known location (waypoint).
Recording a location, called "marking a waypoint" by Garmin, can be done two ways. One would be to enter the latitude and longitude manually. The field ethnobotanist is more often recording a location at which a plant is found. Setting a waypoint at one's current location is fairly easy. On the Foretrex 201 one simply holds down the button labeled "mark" (this is also the "enter" button). After a couple of seconds the waypoint page appears.
Press enter again to accept the waypoint without modification.
To navigate to pre-recorded waypoint, press the "goto" button on the unit. This will cause the "List All" waypoints page to appear.
Scroll to the desired tab. Note that waypoints are organized in subscreens alphabetically. To find a waypoint beginning with an "F" one must select the A-H tab in the waypoint "list all" screen. In the image the user has scrolled to the A-H screen to select the FACLTY waypoint (faculty building). Press enter in order to scroll through the list of A-H waypoints. The up and down arrow buttons usually move one up or down on a page.
Press enter to select the FACLTY waypoint. The Foretrex will change to the compass and bearing page to show the direction to the FACLTY waypoint. You must be MOVING for the bearing to be accurate: the Foretrex does not know which way it is "pointing." You must WALK forward and keep WALKING in order for the unit to remain oriented.
Once one has selected a waypoint to "goto," the mapping (also called track) screen shows the direction to the waypoint via a thicker line as seen in the diagram. The person is moving towards the "top" of the page. Behind the person - representing your location - a trail of "breadcrumbs" is left behind. Holding the Foretrex in front of one on their wrist, the thick line shows the direction to go to get to the selected waypoint. Again, this works only if one is MOVING: one must WALK or run or move in order for the thick line to point in the correct direction! Note that the breadcrumbs to the left of the person in the image was an earlier track made by that person when they were traveling in the opposite direction.
The following exercise has two overall goals: