U.S. National Grid Emergency Location Markers (ELMs)

Basic background information on the USNG system is available here:

http://usngcenter.org/elm-background/

The main reason for using USNG is that the markers (ELMs) and the format are easily read in a panic situation and the information can be conveniently and accurately transmitted via voice or text.

The current WGS84 standard, commonly used in many navigation devices, can be confusing especially to those who are not familiar with latitude and longitude.

The readouts on some devices (GPS, smartphone, etc.) display longitude then latitude instead of latitude and longitude. Which number is which? It often isn’t clear. Some units omit the third digit necessary for accurate longitude as in 75 degrees rather than the correct 075 degrees. Some use polarity symbols as well.

There is no standard latitude / longitude readout format on navigation devices which often causes confusion when reporting field coordinates during stressful situations. Responders often have to convert the reported information to another format (usually USNG) which takes precious time and may cause transcription errors.

The US military developed the Military Grid Reference System (MGRS) during WWII for many of the above reasons. The USNG system is based on the MGRS.

Luckily, most navigation devices will read out in many different formats and there are a host of smartphone apps available that will quickly convert between formats.

There is absolutely NO difference numerically, geographically, or in accuracy between the numbers "75" and "075". Leading zeros are dropped by any computer code which would process the coordinates. Leading zeros (as opposed to trailing zeros: 75.0 is NOT the same as 75) add nothing to the accuracy of a number.

I did not say there was a difference in accuracy between 75 and 075. Depending on the unit or system, the 3rd digit is often required when entering correct longitude

My point was that it just adds to the confusion for someone who isn't familiar with the WGS coordinate system when relating the coordinates to an emergency responder.

"Some units omit the third digit necessary for accurate longitude as in 75 degrees rather than the correct 075 degrees."

Ummmm, yeah, you did. In so many words.

I could have constructed the sentence differently. I was referring to the INPUT accuracy, not the position accuracy.

Sorry for the confusion.