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Old 20-04-2009, 00:22   #1
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more help maybe?

As i said very new to gps, have looked up some Boat ramps and stuff as reference .....gps points given on a google search for certain ramps and areas don't seem to match maps,.. in some cases its a little out but in others it seems miles out, also when entering coord's some for example will be given as 38.11.568 S 145,11.875 E others with only 2 number endings.. maxsea asks me to enter 4 number endings......does .875 translate to .8750....?

Once again any help would be great.....

Mark.
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Old 20-04-2009, 06:24   #2
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In the example above, yes, .875 is the same as .8750.

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Old 20-04-2009, 07:34   #3
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You need to be very careful when reading charts and or inputting coordinates. Most likely the culprit is the way the chart displays data. Some use degrees and fractions of degrees, Others use degrees, minutes, and seconds. Big difference..
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Old 20-04-2009, 16:39   #4
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Yes because mathematically 0.875 is treated the same as 0.8750
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Old 20-04-2009, 19:08   #5
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Quote:
Originally Posted by rtbates View Post
You need to be very careful when reading charts and or inputting coordinates. Most likely the culprit is the way the chart displays data. Some use degrees and fractions of degrees, Others use degrees, minutes, and seconds. Big difference..
Good point, but 0.875 is obviously decimal minutes not seconds.
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Old 21-04-2009, 03:53   #6
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HI Mark,

Have you checked both programs are using the same L&L method? Are both on "Degrees, Decimal Minutes"

Maybe try some of the other settings in Options / 3D View


I have found Google more accurate than charts.
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Old 21-04-2009, 07:51   #7
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Mark, I assume you're aware of the conversion of "minutes" of latitude to the decimal system and are using 0.5 to represent 30 minutes.
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Old 21-04-2009, 08:50   #8
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It represents 30 seconds.

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Old 22-04-2009, 08:32   #9
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GPS accuracy is also affected by the accuracy of the map you are using. All maps are geo-referenced to fixed points on earth. How accurately that is done greatly affects what you see on Google Earth or any of the ENC or Vector charts commercially available.

You will often see a chart plotter representation of your boat that has you sailing across the beach instead of your actual position safely within the channel. Is this due to GPS inaccuracy or poor map geo-reference? The answer is YES.

GPS accuracy and how well the company's mapset have been 'tied' to the earth all affect the representation of where the GPS "thinks you are." To be safe, assume that the GPS gets you close - the rest is up to your good old MK 1 Mod 0 eyeball. If you are standing in the parking lot, yet Google Maps shows you on the boat ramp, which one of your sensory inputs will you believe?

That is a key phrase with GPS - where it "thinks you are." One or 2 groundings is all it takes for you to remember this fact...
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