How different is aviation GPS?

Paul Tomblin wrote:
Years and years ago, I was told how to access some diagnostic modes on my
Garmin GPSMAP 195. The diagnostic mode showed the state of all sorts of
internal stuff, and from that it was apparent that one major difference
between the aviation 195 and the marine 175 is that the 195 had
temperature and pressure sensors. I suspect they put that in there so
that they could correct the results from the GPS radio for those factors.
The other major difference was that the 195 had WAY more flash memory to
store all those aviation waypoints.

Paul,
Do you happen to remember what the keystrokes were to get to the 195's
diagnostic mode? I'd be curious to see what mine is saying.

--- Jay


--

Jay Masino "Home is where the critters are"
http://www.JayMasino.com
http://www.OceanCityAirport.com
http://www.oc-Adolfos.com

Paul Tomblin wrote:

Years and years ago, I was told how to access some diagnostic modes on my
Garmin GPSMAP 195. The diagnostic mode showed the state of all sorts of
internal stuff, and from that it was apparent that one major difference
between the aviation 195 and the marine 175 is that the 195 had
temperature and pressure sensors.

I've had several handheld, general purpose / outdoor GPS units that gave
temperature and possibly (I don't clearly remember) pressure in
diagnostic mode.

Many newer marine units have external water temperature, depth sensor,
and water speed sensor capabilities, as well as the same memory
capabilites as aviation units. While airplanes need aviation waypoints
and related information, boaters need serious waterway chart storage, so
memory is just as important. The better marine units have the
waterborne equivalent of our VFR charts stored and displayed by the
unit. I really think price differences have more to do with our $70
inner tubes and $50 carriage bolts than technology differences.

Here's one link to diagnostic modes, use at your own risk:
http://www.gpsinformation.org/dale/secret.htm

The rest of the site:
http://www.gpsinformation.org is got enough info to spin your head! G

We've flown with a Garmin 196 next to an eTrex Vista and a 60CS (with an
included magnetic compass and barometric altimeter), the 196 was no more
accurate than the $3-400 handheld units. My co-owner has the marine
clone of the 296, loaded with "BlueCharts", and the unit is just as
accurate, feature laden, and powerful as the aviation model.

wrote in message
oups.com...
As part of my work (civil engineer), I routinely use GPS equipment in
surveying. And construction specifications usually calls for this
equipment to be held stationary for as much as three hours where
crucial transition points are to be located, and for up to twenty
minutes at less important locations.

I guess since you folk use GPS to navigate all across the globe and
requires to be both very precise and instantaneous, my equipment is
very much inferior to what's used in aviation.

Has anyone here used the type of equipment I'm mentioning? You should
see the time the thing I use takes to stabilize itself to show the
elevation... you'd comfortably CFIT if you had that in your airplane
)

Aircraft GPS systems are accurate to about 30 feet; how well do you think
that would work if your building a bridge, or more importantly, a tunnel?

Matt Barrow wrote:

Aircraft GPS systems are accurate to about 30 feet; how well do you think
that would work if your building a bridge, or more importantly, a tunnel?


Some, maybe even many, aviation units can get far better accuracy with
differential and WAAS corrections.

In article ,
B A R R Y wrote:

Many newer marine units have external water temperature, depth sensor,
and water speed sensor capabilities, as well as the same memory
capabilites as aviation units. While airplanes need aviation waypoints
and related information, boaters need serious waterway chart storage, so
memory is just as important. The better marine units have the
waterborne equivalent of our VFR charts stored and displayed by the
unit. I really think price differences have more to do with our $70
inner tubes and $50 carriage bolts than technology differences.

Marine units (at least the high-end ones) often have tide charts built into
them too. Unlike winds aloft, tide heights and tidal currents are very
predictable and can be calculated years in advance. A good GPS unit will
have these tables built in, and can superimpose on the displayed chart a
field of current vectors, and tidal water depths.

Marine units also have a feature which is very handy on a boat, but more or
less useless on an airplane (unless you're hauling skydivers). Hit the MOB
(Man Over Board) button, and the unit will immediately store your current
position as a user waypoint and start navigating to it.

They also often have an anchor watch feature, which sounds an alarm if you
ever get more than N feet away from your current position. You do then
after you've anchored to alert you to the possibility that your anchor is
dragging (you set N to however many feet of rode you've put out).

Oh, yeah, and marine units tend to be waterproof. I don't know of many
aviation units that are designed to 1) float, and 2) survive be submersed
in salt water.

wrote:
Bob Noel wrote:
[snip]
Has anyone here used the type of equipment I'm mentioning? You should
see the time the thing I use takes to stabilize itself to show the
elevation... you'd comfortably CFIT if you had that in your airplane
yeah, but what is the accuracy of your GPS?
I suspect it is much more accurate than needed for aviation.


Not really Bob. Most building, refinery and pipeline surveys accept a
+/- 0.8 centimeter variation, so it isn't pinpoint like in aircraft, I
think.

I had my property surveyed and asked what the accuracy was. The
surveyor replied that 0.1 foot is the standard for most applications and
0.01 foot is required for commercial, high-precision applications.
They use GPS (DGPS??) but I don't know how.

Aircraft systems are designed to rather wide standards,
measured in meters and not the centimeter accuracy of a
surveyor's system. An aviation GPS will lock on to all
visible satellites and begin giving navigation solutions
within just a few minutes. The aviation and
automotive-marine-hiker GPS include a navigation computer
and will to some degree do all the calculations and display
results. Your impression about aircraft accuracy is 100%
backwards.


You can find the specifications for GPS systems on the
Garmin or other makers web sites.


wrote in message
oups.com...
| Bob Noel wrote:
|
| [snip]
| Has anyone here used the type of equipment I'm
mentioning? You should
| see the time the thing I use takes to stabilize itself
to show the
| elevation... you'd comfortably CFIT if you had that in
your airplane
|
| yeah, but what is the accuracy of your GPS?
| I suspect it is much more accurate than needed for
aviation.
|
|
| Not really Bob. Most building, refinery and pipeline
surveys accept a
| +/- 0.8 centimeter variation, so it isn't pinpoint like in
aircraft, I
| think.
|
| Btw, just out of interest - does TCAS use GPS data in some
ways too?
|
| Ramapriya
|

Roy Smith wrote:
In article ,
B A R R Y wrote:

.....
Hit the MOB
(Man Over Board) button, and the unit will immediately store your current
position as a user waypoint and start navigating to it.

We use the MOB feature to memorize where we parked the car while
Geocaching. Also, MARK saves a point on a route list. We "drop a mark"
every time a decision (to turn etc) is made. The route can be reversed
to get back to the car.

wrote:
As part of my work (civil engineer), I routinely use GPS equipment in
surveying. And construction specifications usually calls for this
equipment to be held stationary for as much as three hours where
crucial transition points are to be located, and for up to twenty
minutes at less important locations.

I guess since you folk use GPS to navigate all across the globe and
requires to be both very precise and instantaneous, my equipment is
very much inferior to what's used in aviation.

Has anyone here used the type of equipment I'm mentioning? You should
see the time the thing I use takes to stabilize itself to show the
elevation... you'd comfortably CFIT if you had that in your airplane
)

Ramapriya


In addition to what every one else mentioned, aviation GPS also has a
feature known as RAIM which stands for Receiver Autonomous Integrity
Monitoring. It warns you of any problems with the satellite signals.
Some have RAIM prediction as well.

"B A R R Y" wrote in message
. net...
Matt Barrow wrote:

Aircraft GPS systems are accurate to about 30 feet; how well do you think
that would work if your building a bridge, or more importantly, a tunnel?

Some, maybe even many, aviation units can get far better accuracy with
differential and WAAS corrections.


WAAS will provide about 10 feet, but that only for approaches with WAAS
augmentation.

See nice graphic at http://www.garmin.com/aboutGPS/waas.html