Very good - I'm surprised CM didn't know this because its rather fundamental. Basically,
features will be wider on the screen by the beam width. "Inside" features, such as a cove
or entrance that are smaller than the beam width will disappear. Buoys that are closer
together than the beam width will merge. As you point out, RB wouldn't see the entrance
at Port Jeff until he's within a mile.

This is the real reason to get larger antennas, which have a smaller beam width.

BTW, where did you get your numbers? They correspond to statute miles. We use nautical
miles here, not baby miles.


Simple Simon wrote:
That's easy - here's a more complete answer than the other
one I just gave you.

Beam width is important in bearing resolution. All targets are
widened by
the effective horizontal beam width. If the beam width is 4 degrees,
two
targets that are one mile off will appear as one if they are closer
together
than 370 feet. At two miles the targets must be separated by 740
feet, at 24
miles a six degree beam width would merge objects that were almost
1.68 miles
apart. This can make interpretation of the display difficult.
Suppose you
are trying to find a harbor mouth that is 370 feet wide. Radar won't
pick it
up until you get closer than a mile.

Get it?

S.Simon - a Captain who's a navigational phenom.

"Jeff Morris" jeffmo@NoSpam-sv-lokiDOTcom wrote in message
...
So perhaps you or Neal can explain to everyone how the horizontal
beam width affect the image.

-jeff


Capt. Mooron wrote:
Most people I've seen either find a radar image intuitively correct
to what they see around them ... or they don't. I knew immediately
what I was looking at on the first radar image I saw. I can
interpolate between radar, air photo and chart in an instant. I
mentally compensate for differences in scale and orientation. Maybe
I'm one of the lucky few... but I assumed everyone had this ability
to some extent.

CM

"Simple Simon" wrote in message
...

But radar is different from a paper chart because
a paper chart does not foreshorten the view while
radar does. Radar is really no different than a
looking at something with eyes that use radio
waves instead of light waves

Our eyes use light and when we see a hundred
yards of water at a distance of a quarter mile this
hundred yards of water looks a helluva lot shorter
than the same hundred yards right off our bow.

Radar 'sees' thing the same way so one must
extrapolate this information mentally in order
to match it with a chart of the same area.

It would be much the same as equating a gnomic
projection with a Mercator projection but backwards
if looking north on a Mercator.

See what I mean? But the point is the majority
of people can't even imagine such differences
let alone work with them.

This is what I mean by spatial comprehension.

S.Simon - a sailboat Captain who's superior to any and all
motorboat Captains

"Capt. Mooron" wrote in message
...
Generally I find that women are at a loss when it comes to spatial
comprehension. A man will usually automatically know the extended
limits of an automobile when he sits in one. Women depend on
mirrors and the visual depth of field at a specific spot to
determine this. This is one of the reasons why women generally do
not back into a parking space... while men prefer to. I say this
is a general trait.... I know of women who are very good with
spatial interpretation.

If you look at the radar screen as a chart... it is easier to
resolve the image and blend it to the area around you. Just keep
in mind that often you only view the proximal reflected surface
of any object. The "chart" on a radar screen is always oriented
to the line of the vessel and bearing is always relative unless a
fluxgate compass or GPS input is available. In a day or two I
could easily have you running with a full comprehension of
radar... at least as well as anyone else. Tuning radar is no
problem....

CM

"Simple Simon" wrote in message
...


I've met many people who cannot extrapolate a land map
of an area they are familiar with much less be able to relate
to a nautical chart. If tests were given for this type of
relating a graphical representation to geography I bet you'd be
apalled at the numbers of folks who simply can't relate.

Bobsprit is probably one of these chart challenged people.

Simple things like basic orientation of the map while they
look at it leaves them at a loss. A radar display is even
more of an alien representation that a paper chart. Is the
display 'heads up' or "oriented north" for instance is more
than many people can cope with. Spatial relationships
and representative distances with respect to scale are
concepts many simply cannot fathom. I've only used
radar a couple of times and found it did not convey
much information at all other than skewed and foreshortened
spatial relationships that were difficult to stretch out into
geographical reality in my mind - a mind which excels
at spatiality.

I can see where practice, practice, practice and a mind
that can understand is vital for a radar operator. This is
yet another reason I think there should be a navigator at
the helm of large ships. Let the navigator navigator - let
the Captain steer according to input from the navigator.

S.Simon - a Captain who knows how things work




"Capt. Mooron" wrote in message
...

"Shen44" wrote in message

Radar is an aid to navigation, that is well learned if one has
one,
but
not as
important to learn for beginners, as some of the other basics,
such as compass, chart work, etc..
Contrary to what some may think, radar is not something you can
just
turn
on,
for the first time, and be instantly familiar and competent
with it's usage. I have seen any number of people using it on a
fairly regular
basis,
who
have
problems tuning (and sometimes detuning) for best picture, then
equating that picture to their charts or vessel traffic around
them.
Without knowing the basics of relative motion and how to plot
targets,
you
can
easily get yourself into as much trouble as you can avoid.

Maybe these people are the same ones with spatial difficulties.
I haven't seen anyone that has had a problem understanding a
radar image... tuning radar is a little more complicated ...
but not out of the realm of the newbie.

While I concur that Basic Navigation is primary obstacle to
overcome... a radar in use to confirm your plots and verify
relative bearings is perfectly fine.

The days of high tech being utilized only on large ships is
over. Navigational instrumentation is now available to the
layman and the general population's ability to embrace
technology has increased dramatically.

CM