GPS Coordinates (format) for SAR, especially for DSAR

[AlabamaDroner]

I have been wondering, is there a standard format for GPS coordinates for SAR? And, is there a reason to prefer one over the other?

 

[sar104]

There is no standard format. Most ground searches are run using UTM coordinates under the WGS84 datum, although in some areas the 7.5' quads are still NAD27, so that get's used too. In some areas those datums can differ by a couple of hundred meters. Air operations are exclusively done in lat/long, typically decimal degrees. The datum is mostly irrelevant in lat/long.

Consumer GPS units mostly default to WGS84, but can be set to NAD27. The biggest problem that I find is that most people barely know the difference and don't know how to check or change that setting.

 

[Thoraldus]

I have been wondering, is there a standard format for GPS coordinates for SAR? And, is there a reason to prefer one over the other?

Our group is standardizing on degrees.decimal as that is used by our helicopter support. We just had a training session on converting all the formats back and forth. We want our SAR members to be fluent in all LAT/LONG formats.

 

[sar104]

Our group is standardizing on degrees.decimal as that is used by our helicopter support. We just had a training session on converting all the formats back and forth. We want our SAR members to be fluent in all LAT/LONG formats.

I think that they should be familiar with both coordinate systems, but lat/long is not as well-suited as UTM to ground search. The quads all use UTM grids, accurate interpolation of lat/long is much harder, and UTM is much more easily related to actual distance on the ground.

 

[Thoraldus]

I think that they should be familiar with both coordinate systems, but lat/long is not as well-suited as UTM to ground search. The quads all use UTM grids, accurate interpolation of lat/long is much harder, and UTM is much more easily related to actual distance on the ground.

Sorry I wasn't more clear above. Internally we use UTM for ground search, but talk DDD.DDD when talking to external agencies.

 

[sar104]

Sorry I wasn't more clear above. Internally we use UTM for ground search, but talk DDD.DDD when talking to external agencies.

Okay - that's exactly how we do it too.

 

[BigAl07]

Sorry I wasn't more clear above. Internally we use UTM for ground search, but talk DDD.DDD when talking to external agencies.

I think that's about as close to a "standard" as you'll find.

 

[kadras]

I have been wondering, is there a standard format for GPS coordinates for SAR? And, is there a reason to prefer one over the other?

In general, US ground SAR prefers UTM/MGRS/USNG, air and maritime SAR prefers lat/lon. As for lat/lon format...

Both the 2018 US National Search and Rescue Supplement to the International Aeronautical and Maritime SAR Manual and the 2019 Australian National SAR Manual define position as "A geographical location normally expressed in degrees and minutes of latitude and longitude."

The Land SAR Addendum to the US National SAR Supplement uses the same definition. It expands on that "During SAR operations (and to avoid confusion) Latitude and Longitude should be in one standard format: DD-MM.mm. If required, use up to 2 digits to the right of the decimal. If required, allow 3 digits in the degrees field for longitude (i.e., DDD-MM.mm)."

The US Coast Guard addendum states: “Lat/Long in degrees, minutes and tenths of minutes.”

US Chairman of the Joints Chiefs of Staff Instruction 3900.01 Position (Point And Area) Reference Procedures "latitude and longitude, will be expressed in degrees, minutes, and decimal minutes (DDMM.mmmm)."

The international Cospas-Sarsat satellite system reports coordinates in DD MM.m, (one digit to the right of the decimal) for LEOSAR, MEOSAR, and Confirmed Position (formerly know as Merge or Composite) derived locations. Encoded positions (from GPS) are DD MM.mm (two digits right of the decimal). However the two digits won’t be from .00 to .99, the system limits them to increments of 4 seconds, so .00, .07, .13,…., .80, .87, .93..

In Colorado the unwritten accepted practices in the SAR community are DD MM.mm for the fixed wing and helo crews, and is the format that they expect to receive the coordinates, and UTM for ground SAR.

Computer and GIS types like decimal degrees DDD.dddddd.

FAA doesn't have a consistent practice on the format for lat/lon.

 

[AlabamaDroner]

Thanks for the input. I knew there’d be a wealth of information here. I’m basically feeling like we should just make sure we’re familiar with all the formats.

 

[kadras]

Thanks for the input. I knew there’d be a wealth of information here. I’m basically feeling like we should just make sure we’re familiar with all the formats.

Yes, you'll run into all of them, and depending on where you are, some formats will be used more than others.