Coordinates for Sarsat Hits

[sardak]

This poll is prompted by a recent discussion on a SAR lister.  It had to do with a PLB mission and the coordinate format that Sarsat hits are in.

As a bonus question, what datum are the coordinates in?

Mike

[CadetProgramGuy]

D:M:S, plus or minus a state.......

[Al Sayre]

Every time I talk to them (about once a week), I get degrees, minutes, tenths of a minute.

[sparks]

I'd be happy if the alerts weren't 5+ hours after the ELT was noticed by various airline pilots and private aircraft.

[lordmonar]

The Datumn should be WSG 88 IIRC.

[isuhawkeye]

this really doesn't nead to be a pol.  I've only ever seen them do it 1 way.

[ctrossen]

this really doesn't nead to be a pol.  I've only ever seen them do it 1 way.

Correct. Degress, Minutes, tenths of Minutes. That's the only way I've ever received coordinates from a controller.

Now, the difficult part comes when giving specific assignments to a G-1000 aircrew. The G-1000 default is Deg, Min, Sec. If the crews don't actively remember that, there may be some issues. (Then again, one would hope that someone would realize something is wrong when they can't enter N43 13.7  W88 24.85 as a waypoint.)

[Al Sayre]

It's simple enough to convert them before you give them out... 0.1 Minutes = 6 seconds.

[RiverAux]

the last time I looked, and this was with an Apollo GPS, they were set to NAD27 datum.  If AFRCC is using something different it will cause a small discrepancy.  Probably not enough to affect an aircrew though.  What datum is the g1000 set to?

[sardak]

this really doesn't need to be a poll.  I've only ever seen them do it 1 way.

Correct. Degrees, Minutes, tenths of Minutes. That's the only way I've ever received coordinates from a controller.

Degrees, minutes, tenth of a minute is correct.  DDD MM.m
The Sarsat system generates them in that format before they are given to any RCC.

Unfortunately, what prompted this poll was a mission in which the coordinates in this format were read to the non-CAP SAR organization as degrees, minutes, seconds.  This created confusion at both ends of the conversation and to the teams in the field.

As part of the after action review, a poll similar to this one was conducted within AFRCC.  The results were "disappointing" according to the commander.  He asks:
a. That everyone understand there are some relatively inexperienced controllers.
b. That if there is an issue, concern or possible misunderstanding during a mission, request that an AFRCC supervisor join in the conversation then, not after the mission.

As for the datum, that question was posed to the controller during the mission.  The question just added to the problems because no one knew.  The reason it was asked is because most USGS 7.5 minute topo maps are drawn to NAD27, and that's what the field teams were using.

The FAA works in NAD83 and WGS84 and the DoD works in WGS84 (unless some specific theater operation requires a local one).  Unless you're a surveyor, NAD83 and WGS84 can be considered equivalent.   But there can be a difference of up to a hundred meters or so, depending on the location in the US, between a position in NAD27 and WGS84/NAD83 if the datum of the map and position aren't the same.  All handheld GPS receivers can do the conversion, as well as a number of computer programs.

I can't speak to RiverAux's comment specifically, but the Apollo and Garmin aviation GPS manuals I've looked at, including the one for the G1000, all state that the datum is WGS84 and is not user selectable, which makes sense.

Here's a brief article on this search: PLB Search

Mike

[RocketPropelled]

....and another good example of What To Put Into a Decent Mission Brief.

Make sure the GT types and the aircrew are either a) working on the same datum (WGS84 works nicely), or b) someone's converting their numbers to an appropriate format.

[Nick]

This poll is prompted by a recent discussion on a SAR lister.  It had to do with a PLB mission and the coordinate format that Sarsat hits are in.

As a bonus question, what datum are the coordinates in?

Mike

MGRS (WGS84)!

Oh, sorry... wrong SAR.