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CAn someone clarify the difference between refresh and redraw rates?

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CAn someone clarify the difference between refresh and redraw rates?

Old 12-04-2003, 04:03 PM
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Default CAn someone clarify the difference between refresh and redraw rates?

I'm a little confused. My old GPSMap 215 has served me well except for one annoying problem. As I circle a spot, it takes seconds for the cursor to catch up to the actual boat position. Not really an issue when I'm cruising to a spot, just when I'm trying to get right on it (within 10ft). Do the new machines still have that problem? I'm looking to upgrade to a garmin2006 or a furuno1732 radar/plotter, but I don't want to wait for the machine to catch up with my actual position. Any help would be appreciated.
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Old 12-04-2003, 04:32 PM
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Default CAn someone clarify the difference between refresh and redraw rates?

Refresh rates are the hertz your screen runs at - the amount of flicker is the best way I know to describe it. Low refresh rates flicker a lot, high refresh rates don't flicker much.

Redraw is how fast the screen updates with new info, such as the chart moving and "redrawing" itself in the new position.

To experiment with flicker right-click on your computers desktop, then adjust your monitor's refresh rate to a lower setting. You will see the screen noticeable flickering. It makes me sick and dizzy when I have to use a screen that flickers like that.


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Old 12-04-2003, 06:08 PM
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Default CAn someone clarify the difference between refresh and redraw rates?

Refresh rates are the hertz your screen runs at - the amount of flicker is the best way I know to describe it. Low refresh rates flicker a lot, high refresh rates don't flicker much.

Redraw is how fast the screen updates with new info, such as the chart moving and "redrawing" itself in the new position.

To experiment with flicker right-click on your computers desktop, then adjust your monitor's refresh rate to a lower setting. You will see the screen noticeable flickering. It makes me sick and dizzy when I have to use a screen that flickers like that.



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Old 12-04-2003, 06:41 PM
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Default CAn someone clarify the difference between refresh and redraw rates?

I think you guys are starting to flicker
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Old 12-04-2003, 06:54 PM
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Default CAn someone clarify the difference between refresh and redraw rates?

Pete,

I went from a 210 to a 2006. It was like night and day. You will be pleased, don't worry.

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Old 12-04-2003, 07:36 PM
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Default CAn someone clarify the difference between refresh and redraw rates?

One other thing you may notice is that your heading (if your chart shows a boatlike image indicating your position) will take a while to become accurate if you are turning at a slow rate.

The only way to fix this is with an electronic compass feed into the gps (assuming you unit doesn't have one built in, most don't).

The GPS doesn't actually know which way your boat is facing. It assumes the direction you are heading is straight ahead, so even if you are drifting backwards it will show the point end of the directional arrow pointing that way. And since it has to take multiple readings to determine which direction the boat is heading, it doesn't update all that quickly.

That can be REALLY confusing if you have no external reference points to fix on (dead night, fog, etc). Always use your compass to see which way you are facing, not your chartplotter.

** yeahah **
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Old 12-04-2003, 08:00 PM
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Default CAn someone clarify the difference between refresh and redraw rates?

PeteH,

Does your unit have an adjustable smoothing filter for the gps that may be set too high?

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Old 12-05-2003, 04:08 AM
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Default CAn someone clarify the difference between refresh and redraw rates?

Thanks for the info. I don't think it has a smoothing filter, but I'll look.
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Old 12-05-2003, 08:26 AM
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Default CAn someone clarify the difference between refresh and redraw rates?

Whoops, forgot what the question actually was. I'm not real sure on this but I think it goes like this. The refresh rate refers to how fast a complete screen can be replaced by a succeeding version. By contrast the redraw rate is really only applicable to fish finders where the first line on the right is drawn and then all the succeeding lines moving to the left are redrawn. Basically how fast it can possibly inch off the screen.

I might very well be wrong in those definitions but that's what I thought they meant.

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Old 12-05-2003, 09:39 AM
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Default CAn someone clarify the difference between refresh and redraw rates?

It is probably redraw speed you are after. But a lot has to do with the software of the particular unit and how it updates the screen. The Northstar units are so fast because they only redraw whatever has changed, while Furuno units redraw everything and consequently if you zoom or pan a bit, there is a bigger lag.

The smoothing filter most definetly will have a big effect on the problem you identfied. If you have the unit set to 1 second averaging, it will recalculate and display your position in 1 second intervals. If you set it for 10 seconds, you would notice a big lag between where the boat is and the position shown on the display. Both the Garmin 2006C and the Furuno Nanvet units have adjustable smoothing. In fact, you can turn it off altogether and go real-time, but then the redraw rate becomes the limiting factor.
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Old 12-05-2003, 10:55 AM
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Default CAn someone clarify the difference between refresh and redraw rates?

OK. I don't see anything about the averaging on my 215D. Basically, I assume either new unit (furuno or 2006) will be substantially faster than my existing unit.
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