GPS Format differences

[Mark Mocho]

n another thread, I briefly touched on the need to use the proper coordinate format when reporting things like landout position. There are three main formats used by GPS. Many are familiar with the traditional "Degrees, minutes, seconds" (DDD.MM.SS), but the default used by most Search and Rescue personnel is "Degrees, decimal degrees" (DDD.dddd). These are definitely NOT interchangeable and can give wildly different locations. The issue is switching from a system using Base 60 (60 minutes to one degree) to a Base 10 (10 or 100 or 1000 0r 10000 units per degree). As an example, I used Google Earth to drop a pin at a point at Moriarty airport. The point is at 34 degrees 59 minutes 38.65 seconds N, 104 degrees 59 minutes 36.68 seconds W. Using the same numbers, I entered them in the "Degrees, decimal degrees" format (34.5938 N, 104.5938 W) and dropped another pin. The points are 35.68 miles apart. See illustraion below. Make sure everybody is on the same page, or you might turn a retrieve into a major problem!

[Mark Mocho]

I forgot to list the third format used by GPS. It is "Degrees, decimal minutes" (DD.MM.mmmm). This is close to the "Degrees, Minutes, Seconds" format (DD.MM.SS.ss) but can still give position differences of a mile or so. The issue revolves around points that are close to the limit of 60 minutes per degree and 60 seconds per minute. If the position is right at an even degree like 35.00.00 ,105.00.00, there is no position error. But when you get close to the next degree and second (34.59.59, 104.59.59) the difference is significant.

[Stefan Will]

But the decimal representation of 34:59:38.65N 104:59:36.68W is 34.9941N, 104.9935W (the fractional degrees for 59 minutes is 0.983, not 59…

I think we would all be in real trouble if the decimal and DMS coordinates were that far off.

On Jun 11, 2026, at 9:23 AM, Mark Mocho <markm...@gmail.com> wrote:



In another thread, I briefly touched on the need to use the proper coordinate format when reporting things like landout position. There are three main formats used by GPS. Many are familiar with the traditional "Degrees, minutes, seconds" (DDD.MM.SS), but the default used by most Search and Rescue personnel is "Degrees, decimal degrees" (DDD.dddd). These are definitely NOT interchangeable and can give wildly different locations. The issue is switching from a system using Base 60 (60 minutes to one degree) to a Base 10 (10 or 100 or 1000 0r 10000 units per degree). As an example, I used Google Earth to drop a pin at a point at Moriarty airport. The point is at 34 degrees 59 minutes 38.65 seconds N, 104 degrees 59 minutes 36.68 seconds W. Using the same numbers, I entered them in the "Degrees, decimal degrees" format (34.5938 N, 104.5938 W) and dropped another pin. The points are 35.68 miles apart. See illustraion below. Make sure everybody is on the same page, or you might turn a retrieve into a major problem!

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[Stefan Will]

Or was your point that make sure you know the format before you blindly enter the digits?