We're working on all new "box cards" for the fire company (basically, these are a script for how response for different kinds of incidents are handled) and my task was to get all of the Landing Zones (LZ's) checked, and get their coordinates and a site naming convention done.

Instead of just making something up that seemed right, we took the radical step of asking the helo pilots how they would like us to present them with coordinates.

Here's how we do it now.

LZ Designators for Station 47 are Lat/Long Decimal Format as follows:

DEG.MIN
DATUM WGS-84

To notify dispatch of coordinates for an LZ, tell the dispatcher:

"We are setting up an LZ at "(name of LZ)"
GPS coordinates for as follows:
40.559 Say "Forty POINT FIVE-FIVE-NINER North"
75.122 Say "Seventy-Five POINT One-Two-Two West"

Listen for dispatcher readback and confirm accurate information.

Rather than "Forty" which can be heard as "Fourteen" and "Seventy" being heard as "Seventeen", I'd recommend saying "Four-Zero decimal Five-Five-Niner North", and in the same format I'd recommend, "Seven-Five Decimal One-Two-Two West". Putting it in context, "Fourteen" and "Seventeen" may not make much sense, but break it all down so there's no confusion.

Good point, we'll update.

I would think that method would actually make more since, especially to an aviator helicopter pilot, as that is similar to how numbers/radio frequencies are called out over aviation communications. (I think they say “point” instead of “decimal”, though, but I could be wrong.) Keeping things consistent to the way pilots normally do things could prevent a lot of confusion.

Wait a sec, is that DDD.MMM or DDD.DDD? If the part after the decimal is minutes, i.e. only goes up to .599, I could see that causing problems, especially if you have helo guys from out of the area or otherwise unfamiliar with your system.

Most GPS have a display option of DD.DDD (decimal degrees, not minutes) which will actually give more precision with the sme amount of digits.

Just a thought from someone who uses GPSs but knows next to nothing about flight ops or fire/rescue.

They told us DDD.MMM is all they need.
It's THEIR system we're using, not ours Thats the point here. We asked them.

Martin:

You mean your agency cannot talk directly to the pilots in these situations? I would seem to cut down on mistakes being made.

Our agency (as are most in Idaho) are allowed to coordinate directions, patient updates and landing zones directly to the responding lifeflight helicopter service. Usually, while the pilot is busy flying, the nurse or paramedic will take the information from a ground crew member. This avoids the hassle of trying to relay through several dispatchers.

Take care,

Stargazer

I'm afraid I find these two lines confusing.

The first line says "Lat/Long Decimal Format", which I take to mean degrees and decimal degrees, i.e. 0.5 degrees is 30 minutes, 0.75 degrees is 45 minutes.

The second line says DEG.MIN, which I take to mean the number of degrees followed by a point followed by the number of minutes. This is at odds with the previous line.

Since I have interpreted this incorrectly I am worried that someone else could too, which I think it what WScott (above) was alluding to.

I know you are using someone else's system, which is great (I wish it happened more often) but IMHO the instructions need to be entirely unambiguous so that you can be sure you are using it properly.

Perhaps you have paraphrased the description of the system, inadvertently introducing confusion?

A

I agree, didn't pick up on that before. I assumed the decimal point indicated a DD.DDD format, not a DD.MMM format. I'd use a hyphen rather than a decimal point, but as Martin said:

So, sorry to bring this up, but are you going to clarify this post? If I and two others are confused reading about the system, isn't there a risk that someone using the system might get confused too?

Specifying a WGS84 reference is subject to a lot of misinterpretation.

There are the following ways to specify a global GPS location

There is Degrees Decimal Notation.

DDD.DDDD N DDD.DDDD W
DDD.DDDD N DDD.DDDD E
DDD.DDDD S DDD.DDDD W
DDD.DDDD S DDD.DDDD E

There is Degrees Minutes Decimal Notation.

DDD,MM.MM N DDD,MM.MM W
DDD,MM.MM N DDD,MM.MM E
DDD,MM.MM S DDD,MM.MM W
DDD,MM.MM S DDD,MM.MM E

There is Degrees, Minutes, Seconds Notation.

DDD,MM,SS N DDD,MM,SS W
DDD,MM,SS N DDD,MM,SS E
DDD,MM,SS S DDD,MM,SS W
DDD,MM,SS S DDD,MM,SS E

There are 12 different formats each giving a different location but using the same numeric data

e.g.

45.6763 N 76.6783 W
45,67.63 N 76,67.83 E
45,67,63 N 76,67,83 W
45,67.63 N 76,67.83 W
45,67,63 S 76,67,83 W
45.6763 N 76.6783 E

Are at completely different locations.

This is why in the UK we mostly use Grid Square Referencing OSGB36, as it doesn't lead to confusion.

We have the same issues here in CA. Our searchers us UTM grid coordinates, but pilots use LAT/LON. Having a communications van
to help catch errors is very helpful.

Yes, but the original message specified both of the first two formats you state. Either one is clear, but to use both is conflicting.

I suppose in the UK you can ignore 'S', as it is entirely in the Northern Hemisphere, but you have to get E and W right thanks to that tricky Greenwich Meridian. In the US, GPS positions will always be N and W.

A

Good point. But is always good practice to specify whether your location is either east or west of the Greenwich Meridian an North or South of the equator.

There have been occasions where the UK HM coast guard have recieved emergency rescue calls south of the equator and east of the Greenwich Meridian.

When a using a GPS to call in a emergency location, specifing the coordinate or geodetic system is good practice also.

So, martinfocazio can you please clarify?

Hi martinfocazio,

If using Decimal Degrees notation. i.e. DDD.DDD N DDD.DDD W is the one being specified by the helo pilots I would use the following or something similar for the dispatch sentence format. As most GPS equipment can be setup to display 2 geoedetic coordinate systems i.e. a secondary coordinate system in addition to WGS84 Decimal Degrees. I would also ensure that the second coordinate system is outputing UTM coordinates for all the GPS equipment in use.


To notify dispatch of coordinates for an LZ, tell the dispatcher:

"We are setting up an LZ at (name of LZ)"
"DATUM is WGS84. Decimal Degrees GPS coordinates for LZ is as follows"
"FOUR ZERO DECIMAL FIVE-FIVE-NINER NORTH"
"SEVEN FIVE DECIMAL ONE-TWO-TWO WEST"

OK! I sent a copy of your message to them and they agreed, so there we are.

Martin,
Great call getting the actual stakeholders involved. It can really be enlightening to see the world from their viewpoint.

While I use GPS, even I learned something from the various postings in response to your initial post.