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Wayne.B Wayne.B is offline
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First recorded activity by BoatBanter: Jul 2006
Posts: 10,492
Default Raster vs Vector (Was Electronic Charting)

On Mon, 18 Sep 2006 07:45:00 -0400, "Gerald"
wrote:

I am convinced that raster charts are the way to go and that, perhaps, I
am not in the mainstream and have made it to the position of 'old-fart'.


I hear you, vector charts definitely takes some getting used to, and
for some things raster is clearly superior.

For the last two years I've had both side by side, raster on
PC/Maptech, and CMAP/vector on a Furuno chart plotter. I agree with
much of what you say, but have come to appreciate some of the benefits
of vector as well.

One thing that vector does much better is "zoom in" and "zoom out".
When you zoom a raster chart the text fonts and pixel details get
larger and smaller also, which renders them illegible very quickly.
Vector on the other hand automatically compensates for zoom level so
that font sizes are constant, and detail pixels are adjusted to an
appropriate size. The net result is that fewer vector charts are
required for any given area since detail improves as you zoom in,
unlike raster which requires an entirely new chart to show greater
detail.

The other area where vector is clearly superior, is "course up" mode.
Course-up is a much more intuitve way to view chart data, particularly
in close quarters. However, if you display raster charts "course up"
on anything other than a north bound heading, chart text and symbols
appear rotated out of the normal vertical orientation, and are
actually upside down in south bound directions. With raster charts,
the text and symbols are automatically rotated to stay in normal
orientation, making course-up much more useful.

On our boat I generally do all of my route planning on the PC using
raster charts since Maptech is very good at that, and I can do
everything off-line in the comfort of the main cabin the night before.
While running I keep the PC zoomed out to show the big picture and the
route information such as range/bearing to next waypoint, total miles,
time-to-go, etc. On longer legs I will transfer the next waypoint
details to the Furuno chart plotter as well. The chart plotter is
usually left in course-up mode and zoomed in to a fairly high level of
detail where chart symbols are resonably uncluttered and easily
readable.

Another superior feature of the chart plotter, unrelated to
vector/raster, is screen brightness and clarity. The brightness level
is fully adjustable for comfortable viewing all the way from direct
sunlight to complete darkness. No PC or flat panel display that I
have used has a comparable level of brightness or adjustability.

With the right selection of features and options, the chart plotter
has some other worthwhile attributes. For example our Furuno system
has the ability to super impose radar data on top of the chart display
which is very useful for identifying unkown radar blips and determinig
whether or not it is a navaid or probable boat. Since this feature
requires rotating and zooming the chart data to match the radar
display, vector charts are clearly the right choice.