Glider computers - what's important?

I'm using an elevation database accurate to less than one meter on a 100m
grid. That's far more that accurate enough to provide a glide footprint. I
choose not to display this as a visible map since it make more important
data hard to read and takes processing power. I just display airports,
turnpoints and the glide footprint.

Bill Daniels

"Marian Aldenhövel" wrote in message
...
Hi,

I want my glide footprint on the moving map.

This depends very much on accurate terrain elevation data. I am not sure
how good the publicly available data is. It does paint pretty pictures
in any case.

Elevations for airfields are very accurate and those for charted landouts
at least at GPS-accuracy.

Ciao, MM
--
Marian Aldenhövel, Rosenhain 23, 53123 Bonn
http://www.marian-aldenhoevel.de
"Success is the happy feeling you get between the time you
do something and the time you tell a woman what you did."

Bill Daniels wrote:
I'm using an elevation database accurate to less than one meter on a 100m
grid. That's far more that accurate enough to provide a glide footprint.

What is the advantage of a glide footprint to your soaring? Is it useful
in the mountains, or only in flatter terrain? Knowing I can reach an
unknown patch of ground doesn't sound useful, so I suspect I'm missing
something.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

An "ide footprint"? That was supposed to be "glide footprint"!


--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Eric,

Most soaring software that I have seen simply evaluates whether you will
clear obstacles along the flight path from your current position to the
selected destination. If the route is over Pikes Peak, it doesn't consider
going around it. Is there any software that identifies and calculates the
altitude require for the best route to a field?

Wayne
HP-14 "6F"
http://www.soaridaho.com/


"Eric Greenwell" wrote in message
news:SmgIh.11700$ig.1130@trndny01...
An "ide footprint"? That was supposed to be "glide footprint"!


--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Wayne Paul wrote:
Eric,

Most soaring software that I have seen simply evaluates whether you will
clear obstacles along the flight path from your current position to the
selected destination. If the route is over Pikes Peak, it doesn't consider
going around it. Is there any software that identifies and calculates the
altitude require for the best route to a field?

I don't know of any that does it automatically or even manually in an
easy way. I've encouraged SeeYou to add a feature that lets the pilot
"drag" the middle of the flight path to a new location, so you have an
adjustable two leg flight path around an obstacle. No feature yet.

I think the feature would very useful, and not just for mountains, but
for avoiding airspace, bad landing areas, and poor soaring areas
(wlakes, wet fields, wave or ridge downdrafts). You could also align the
path for good soaring areas.

All of them will let you set up a task to do it, but that's usually a
lot of picking and clicking at an inconvenient time. For repeating
situations, you can add waypoints in passes and valleys to your
database, so it's easier to set up a task in flight.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Eric, it's a matter of laying all options on the table. I have found that
GPS_LOG WinCE showed options that I would not have otherwise considered. It
wasn't a mater of not being able to compute (or estimate) all options, but
of being too focused on the flight plan to see them.

An example is a flight where it had become clear that I wasn't getting home
so the task became getting as close as possible, landing at a convienient
airport to reduce the retrieve distance. Playing back the IGC file on
SeeYou with output to the PDA showed that for about two minutes I had a safe
glide to an airport that would have cut the retrieve by 200 miles of
mountain driving. During those two minutes, I was distracted and didn't see
the option. If I had a glide footprint display, it would have been too
obvious to miss.

A moving map with a glide footprint display is very easy to interpret so I
won't miss good alternatives again. I will never fly without it again even
though I own licenses for Glide Navigator II and WinPilot. If I use those,
it will be on a second PDA showing only the data boxes.

A "glide footprint" shows clearly how to cross a mountain range since it
computes glide distance in all directions. The courseline may happen to
cross the range at a high peak so a list type display will show the goal as
unreachable but the "glide footprint" will show that a slight change in
course will easily clear the terrain.

There is also the case where known lift is available in the distance -
perhaps from good clouds or from radio chatter coming from other pilots. If
this area isn't near an airport, list displays aren't useful. With a glide
footprint it's easy to see when the lift is reachable. Then there's
landable terrain that isn't in the airport database. Just knowing that good
landout options are reachable reduces stress and allows the pilot to
concentrate on the task.

It answers at a glance the question of, "Where can I go from right here,
right now at the current McCready setting?" For everyone who has watched a
simulation of a glide footprint display, there's a big "AHA!" moment.

Bill Daniels


"Eric Greenwell" wrote in message
news:SmgIh.11700$ig.1130@trndny01...
An "ide footprint"? That was supposed to be "glide footprint"!


--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Hi,

What is the advantage of a glide footprint to your soaring?

The programs I've seen determine reachable landing sites along a straight
line only. XCSoar can also show where that direct path would intersect
terrain (computed using a safety margin, so it is not really the point
of impact, but I like to think of it that way).

But it does so only for the current "goto" path, that is along the task set
or to a selected landing site.

The glide footprint simultaneously provides the same information for all
sites on the map.

Ideally it can also tell you wether you can reach a field by "flying
around a mountain" and escape routes when flying in mountains (Although
when I ever get that far in my training I hope to have them ready long
before I get to need them).

I have not checked the programs I tried for this. I suspect they just shoot
a few radials out from the current position and connect the intersections
with terrain they find that way for a closed footprint. A real pathfinding
algorithm sounds too computationally expensive to me.

Ciao, MM
--
Marian Aldenhövel, Rosenhain 23, 53123 Bonn
http://www.marian-aldenhoevel.de
"Success is the happy feeling you get between the time you
do something and the time you tell a woman what you did."

RE-ENGAGING:
Rather than talk about which glide computer program is best... what I
need to know is: What INFORMATION/FEATURES do you experienced guys
find MOST useful in XC soaring.

The most useful thing for me is instant access to safety glide
information. By that I mean knowing what safe landing sites are in
range, the glide margin available, and where they are relative to
current position. Knowing whether it is safe to push on and, if not,
knowing which way to divert, makes a huge difference to cross country
flying.


Andy

Bill Daniels wrote:

A "glide footprint" shows clearly how to cross a mountain range since it
computes glide distance in all directions. The courseline may happen to
cross the range at a high peak so a list type display will show the goal as
unreachable but the "glide footprint" will show that a slight change in
course will easily clear the terrain.

I can use that feature!


There is also the case where known lift is available in the distance -
perhaps from good clouds or from radio chatter coming from other pilots. If
this area isn't near an airport, list displays aren't useful. With a glide
footprint it's easy to see when the lift is reachable.

Actually, this is something I've really wanted, but hadn't thought about
how a glide footprint would help.

Then there's
landable terrain that isn't in the airport database. Just knowing that good
landout options are reachable reduces stress and allows the pilot to
concentrate on the task.

I reduce my stress by carrying an "iron thermal"! But your other points
are well chosen, and I like the idea. I've informed SeeYou it's now on
my wish list.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Eric Greenwell schrieb:

landable terrain that isn't in the airport database. Just knowing
that good landout options are reachable reduces stress

I reduce my stress by carrying an "iron thermal"!

Dangerous tactic. Your personal thermal may or may not work.