Topic: 1198 Problem or problems

[T Hora]

Good Afternoon  I'm new to this forum and a first time poster.  I have a 1198Ci SI mounted in the dash and up dated to 7.670 version . One of the problems I have is I'm unable to get the chart contour lines [Lakemaster Wi version 4 ] and the depth reading on the locator to match any where close. I leave the dock area I match the water depth with contour lines using  the water offset feature, then when I get in the area I want to fish and the depth on the locator and the map contour lines don't match's up at all. The locator will say I'm in 21FOW and the map will show I'm in 30 FOW. Another problem I seem to have is if I get at or below 0.5mph of boat speed the boat icon goes from a boat icon [forward ] to a circle icon [stationary] Another time I noticed I was turning the boat towards on direction and the icon showed I was going the opposite direction and then then the locator corrected itself to right direction. Something tells me it is human error on my side of the equation for the lack of understanding.  If not can anybody give me some suggestions on how go about trouble shooting these issues. Hopefully they are all have a common link and a common  problem   Thanks for your time and help it really appreciated   

[rnvinc]

Inaccuracies in the map data are just that ... inaccurate ...

All map companies interpolate some parts of most maps (http://www.google.com/search?site=&source=hp&ei=azCLVsLDKIbYjwODj4fgBg&q=interprolate&oq=interprolate&gs_l=mobile-gws-hp.3..0i10l5.1671.4196.0.5481.13.13.0.1.1.0.681.4562.2-6j3j3j1.13.0....0...1c.1.64.mobile-gws-hp..6.7.1649.3.XJmNxpzTOco)

This is because it's physically impossible to have a mapping boat on every square foot of every lake on the map card ... Therefore, the portions of the map that wasn't covered by the mapping boat are drawn from other sources (government maps, leased maps from other sources, crackerjack boxes - just kidding on crackerjack lol)...

This is why some of the new self-mapping technologies AutoChart for PC, AutoChart Live) are becoming so desired ...so that fishermen can physically map their own specific waters for more accurate map data ...
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The circle icon (or donut as we call it) is the units way of showing that it doesn't have enough data from the GPS function to indicate movement of the boat ...

Due to inherent inaccuracies of consumer based GPS (because the government doesn't want us to have as accurate GPS as they have) ...and the fact that these GPS systems are not as expensive as surveyors or farmers use... we can only expect accuracy in the GPS of +/- 4.5 meters (from the unit manual) ...

With the GPS refreshing once every 1/5 second ...and the boat traveling very slow ... The boat doesn't move past the +\- 4.5 meters (EPE) between data samples for the GPS function to definitively determine you actually moved ...

So the unit displays a circle to show "I'm waiting for more information before I can determine that you actually moved before I plot the movement on the Chart" ...

The instance you refer to when the icon moved one way and then jumped to the correct way was the unit GPS function "thought" it had enough new GPS data to determine you moved in that direction and then decided to correct itself with even "newer" GPS data ...

Slow speed operation for GPS (in our type units) is basically just very difficult for the unit ...

Rickie