Geographical coordinate systems are methods of encoding locations on the earth’s surface. They derive from the standard latitude-longitude method, called “Lat-Long” for short, which was first developed around the 3rd Century BCE by the Greek polymath Eratosthenes. Many systems have been developed to encode Lat-Long in a more human-readable form. These are called ‘geocode’ systems. We will describe decimal Lat-Long and two geocode systems.
We will confine ourselves to three of these methods:
Latitude/Longitude (Lat-Long) This system originally used degrees, minutes, and seconds of angle. With the advent of the Global Positioning System (GPS), Lat-Long locations are expressed in decimal degrees, using the World Geodetic System (WGS 1984).
For example, 37.90832872733463, -122.3445632042944 corresponds to a location in the middle of Shimada Friendship Park, in Marina Bay, Richmond, California.
Clearly, the 14 decimal places shown above would be overly precise and useless for communication. Using 4 decimal places is more than sufficient for most purposes. For example, the 4-digit version of the above location (37.9083, -122.3445) would enable you to determine that it was somewhere in a circle of approximately 40-foot radius in Shimada Friendship Park—a small park of about 3 acres (130,680 square feet). This blog page has a great description of how the change in the number of decimal places affects the location precision.
What3Words What3Words is a proprietary system which encodes the decimal degrees of Lat-Long using a combination of three English words separated by periods.
For example, ropes.slim.marker identifies a location in Richmond, California very near the Lat-Long location, above.
Plus Codes
Open Location Code (OLC), called "Plus Codes", is a system of encoding that was developed by Google engineers in 2014 and placed in the public domain (See the following link for more information: maps.google.com/pluscodes). One of the stated objectives for this method was to give persons with no formal address for their dwelling to have an address that resembled a postal code. Plus Codes are accepted as legal addresses in several places, including Cape Verde, parts of Kolkata, India, and the Navajo Nation.
For example, 849VWM54+75R corresponds to a location very near the Lat-Long and What3Words locations, above.
One convention for use of Plus Codes is to use only the characters beginning with the 4th character to the immediate left of the + sign and add a named location. For example, in this case, WM54+75R, Richmond, CA would work nicely.
Here’s how to obtain a location in one of the above systems.
Lat-Long & Plus Codes
The Google Maps mobile app can give both Lat-Long and Plus Codes. To obtain Lat-Long or Plus Codes locations open the Google Maps app and navigate to a location. Tap the red symbol showing the location. Scroll down on the page that opens and you will see both a Plus Codes location and a Lat-Long location. Tap the one you want to use and it will be copied to the clipboard.
The Google Maps app and the Google Maps website will also show a location on a map, if you type it in. For example, typing in WM54+75R, Richmond, CA will show you the correct location, as will 849VWM54+75R. This works for Lat-Long as well.
Locations in the Plus Codes format can also be obtained by using the Google Plus Codes website: maps.google.com/pluscodes. On the website, scroll down until you see the “Find Your Code” button at the very bottom of the page. The button will take you to a map with a search box. It is simple to use.
What3Words
You can get a location in What3Words form using the What3Words app or the What3Words.com website. Simply use the search box shown in the website or the app to find a location. You will have multiple possibilities to choose from. For example, you could find the 3-word location nearest the front door of your house or use a nearby street corner.
To show a location using the What3Words format requires that you use the app or the website.
Test of these methods in radio communication
During the 1st Wednesday @ 11:00 o'clock EmComm exercise on 2 February 2022, we compared these methods for reporting location. The goal was to have all participants pre-test their cellphone or computer with these methods and attempt to find a location based on one of three transmitted geocodes:
Each pronounced geocode indicated the same location—Gobbler’s Knob Visitor Center, where Punxsutawney Phil "predicted" how long winter would last. Our first successful on-the-air winner was Marty West [WREP909], who was soon followed by others.
Based on our experience, we suggest that W3W and Plus Codes be avoided as a spoken geocode in radio EmComm.
W3W is subject to misinterpretation, and it takes longer to accurately transmit. For example, operators reported that they ended up in other places like Colorado or Wisconsin. One person heard “cattle.reform.trait” instead of “kettle.reforms.trade” and was sent to a spot in eastern Russia.
Similarly, the Plus Code system uses a mix of letters and numbers and presents its own difficulties in communicating over the radio.
In contrast, a Lat-Long is simply a pair of numbers (to a few decimal places). We no longer plan to use W3W or Plus Codes in future 1st Wednesdays EmComm nets.