On May 23, 10:07*am, Papa3 wrote:
On Thursday, May 23, 2013 9:50:21 AM UTC-4, Dan Marotta wrote:
All good advice, though I question the need for terrain to be displayed vs.
simply looking outside. *Then, again, I fly where the visibility is rarely
*less* than 100 miles. *Perhaps, in other locations, a terrain display
helps.

Certainly in Appalachian ridge country, *terrain maps are hugely useful.. *Knowing which of the 3 low ridges ahead is the one with the valley in
front or which one has the big gap in it is very helpful for newbies to an area.

Additionally, its useful for orienting yourself in terrain or
territory that's confusing or unfamiliar. Major road intersections
and especially Lake shorelines are very distinctive and the human eye
is good at interpreting them even when approaching them from an odd
angle. Mountains, random fields, and small-towns can be
indistinguishable or easily confused for other similar items when
approached from an unfamiliar direction or under certain lighting
conditions. Displaying these major land features on a moving map helps
orient you, relative to the terrain, your desired bearing, and
possible landouts.

Here's a good example: You're 10 miles from a lake, flying towards it
and worried about getting low. You know there is a landout field you
can use near the lake-shore, if things don't improve. You'll want to
ask yourself: Is that known-good-landout-field on the LEFT side of the
lake, or the RIGHT side of the lake? You don't want to fly to the
wrong side and then try to cross the water at low altitude! With an
LCD display, you would probably have to go "heads down" and scroll
through several screens to look at possible landouts nearby and then
do the mental gymnastics based on a bearing to the waypoint, to
determine if the landout field is on the left side of the lake or the
right side of the lake - relative to your current position. With a
moving map you glance at the screen and can SEE the landout field
highlighted, and where it is relative to your positon and the lake.
You can compare what you see over the nose of your glider with the
map, and instantly understand where it is and what you have to do to
fly towards it.

--Noel