What format should I use to report my location to emergency responders?

If you're in Britain, you can either provide GPS coordinates in latitude and longitude as normal, or an Ordnance Survey grid reference which is easily obtained from the maps normally used in Britain. The OS grid is essentially a transverse-Mercator projection, but is not the same as UTM.

Probably mountain-rescue teams would prefer OS grid coordinates, because they will refer to OS maps for their own navigation. However, I expect they also have GPS units which can perform the conversion automatically.

An OS grid reference formally consists of two letters, identifying a general regional grid, followed by six digits (three for eastings, then three for northings) which identify a location within that grid to within 100m. The grid squares marked on OS maps intended for hiking (eg. Landranger series) are normally 1km square; road maps often have 10km squares instead.

There should be a legend on each map explaining how to construct a full grid reference from the map, as well as the local relationship between "grid north" and the magnetic and true norths.

posted over 6 years ago

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Chromatix‭

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Always have a water proof map of the area you're traveling in ( one with coordinates on each side if you can help it ), and a compass you can use to triangulate your position with. You'll be better prepared in an emergency and more confident outdoors in general if you practice triangulating your position until it comes naturally: http://www.rei.com/learn/expert-advice/navigation-basics.html

As a backup, have a reliable GPS, and carry extra ( fresh ) batteries for it, more than you think you will ever need. Obviously having your coordinates in an instant will save you time, but electronics aren't to be trusted with your life.

If you can give your coordinates to dispatchers, you're leaps and bounds ahead of most people that need assistance ( have the dispatcher confirm your coordinates ). Most search and rescue teams have the skill and equipment to translate your coordinates into their preferred format faster than you can even read them.

posted over 10 years ago

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Scott Hillson‭

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In the marine environment, it's often a little easier if you reference a known location. Offshore, you want to use lat/lon coordinates for sure.

But if you're a mile from the coast (or less), it's a lot easier for people to find you if you say "We're a hundred yards south of buoy three, looking at the hotel with the red roof."

I worked for a water rescue service for a bit, and it takes time and clarity to hear a full string of coordinates across a VHF connection. Also, if you're a single minute of latitude or longitude off, that's a big difference. Plus, those same coordinates need to be manually plugged into a chartplotter, which takes time and can't be done while the boat is racing towards you.

But the people who are coming to get you inshore on the water are very familiar with the coastline and will know buoy #3 instantly, and there's no way you're going to know the red roofed hotel unless you're really staring at it.

So while not to discount coordinates, stating what you can see around you is a great confirmation and at least where I worked would get me headed in your direction ~30 seconds faster and with a bit more certainty.

posted over 9 years ago

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Eric‭

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I'd give my position in terms of landmarks ("I'm about five miles up Independence Creek; look for the silver emergency blanket draped over the bushes"). If I had a GPS, I'd also give coordinates in whatever units it displays. If you've ever gone geocaching, you'll know that while coordinates are precise, they don't tell you what the terrain is like or which direction to approach from; landmarks can.

posted over 10 years ago

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Mark‭

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I have twice had problems with this in working with groups in emergencies. The group mistakenly reading decimal minutes as DMS, adding in unnecessary delays in reaching the group. In conversations with lifeflight personnel they say they can use any format, but prefer DMS. All the groups that I work with on policies I insist on them using DMS for that reason.

posted about 6 years ago

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Cliff Stockton‭

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I would recommend UTM coordinates; it avoids the formatting uncertainty of lat/long and is better suited for ground operations. (Easy to translate to paper maps, define search areas, and calculate distances.) If you use the WGS84 datum, the numerical portions are also identical with the military grid reference system (MGRS) and the national grid (USNG). In my area the local mountain rescue groups (BAMRU, Tahoe Nordic) use UTM.

That said, aircraft and ships at sea usually prefer latitude and longitude values as the numbers don't "reset" when you cross zones, and they are usually covering much greater distances than people on land. Per the addendum I added at the end, the recommended format is degrees and decimal minutes. The linked PDF suggests reading coordinates as in the following example (for 39° 36.06’N by 76° 51.42’W): “Three nine degrees, three six decimal zero six minutes North by seven six degrees, five one decimal four two minutes West.”

Regardless of coordinate system, have the person on the other end repeat the numbers back to you; this is one set of numbers you don't want to have an error. Writing down your message before communicating will also help you with a poor connection or low batteries as you'll avoiding wasting time trying to remember what else you need to communicate.

Finally, as others mentioned, the dispatcher should be able to handle any coordinate format, and any search teams will be using topo maps and translating the coordinates to their preferred format. (They are usually familiar with the areas they regularly work in.)

Addendum: I suspected that [within the US] UTM was becoming a SAR standard, as a quick Google suggests that to be the case. Further digging indicates the National Search and Rescue Committee has designated the US National Grid (USNG) system as the standard coordinate system for land-based SAR in the United States, and latitude and longitude (in decimal minutes) for aircraft and boats. This does not mean that some (many?) local agencies are no longer using their older preferred systems; full compliance is probably many years away. If you want to know more about USNG, I suggest posting a separate question, but here's a comparison:

• USNG: 18S UJ 23371 06519

• MGRS: 18SUJ2337106519

• UTM: 18 323371 4306519

(Note that USNG and MGRS use a letter pair for the 100km grid squares whereas UTM doesn't; UTM instead has additional digits. The Easting and Northing values always have the same precision: 3x3, 4x4, and so forth. I personally prefer the USNG style.)

posted over 10 years ago

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requiem‭

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I'd give them whatever my device or map provided me, and let them convert to whatever their devices or maps use. Anyone used to receiving lat/lon coordinates regularly should be able to convert from various formats to whatever they use internally.

You're the one in trouble with limited resources. You're out there with a broken leg, lost, in the cold or dark, or whatever. You're a lot more likely to screw up than someone sitting in a office who is professionally used to dealing with this and probably has equipment that does conversions for him routinely.

You are over-thinking this.

posted over 10 years ago

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Olin Lathrop‭

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