Autochart live gps

[Zippy]

A recent post about the distance of the gps in the head unit and the transducer and the innacuracy that reaults when setting waypoints has got me thinking. Would autochart live contours be off as well if the receiver and the transducer were seperated by any distance? Jsut wondering if I will need a puck if I really want good results.

[rnvinc]

I would think the inaccuracy of the distance difference (antenna vs depth data) would still be happening ...

Each time the unit receives the return echo data (ping) - the unit assigns the current GPS data sample to that packet of Sonar data ...and plots that Sonar depth data on the Chart view background (plotting on the Chart view background happens with or without map data) ...

So the unit is "plotting" that depth data (mapping contours) relative to where the antenna is ...not where the Sonar depth data actually came from (directly under the xducer) ...

GPS antenna sample data is the Chart view background built into the unit ...

Mapping data (including AutoChart Live) is a transparent overlay layer ...

Rickie

[Zippy]

Thanks Rickie. Any reason why Humminbird wouldnt have a head unit transducer offset setting? Seems like that would be an easy update that would take care of the issue. I guess they wouldnt be able to sell the puck at that point whch might answer my question.

I also noticed my build in maps are totally off from my autochart live contour maps. Was mapping the area between two points going from one point to the other to map the channel between them. I was no more that 5 feet from each point when i would turn. When i zoomed out and could see where the land was on my built in map my autochart live contour maps showed my turn well out from the land, close to a full third of the distance between the points. Any idea why they would be so inacurate?

[rnvinc]

There's actually no telling where HB gets the data for their built in Chart background ...

More than likely from old paper charts ...

That's why these "self mapping" technologies are becoming so popular ...people are realizing that the mapping data they have is just not accurate enough for their liking ...

Rickie

[Zippy]

Hmm, interesting.

[rnvinc]

Hmm, interesting.

There's a reason there is a "GPS disclaimer" screen on every bootup of the unit ...

Rickie

[BobB]

Without a heading sensor GPS, the offset would be meaningless, because when creating a map, the offset for the inaccuracy would be dependent on the direction the boat is traveling....and this would make the mapping algorithm much more complicated.

[Zippy]

There's a reason there is a "GPS disclaimer" screen on every bootup of the unit ...

lol, yup

[Zippy]

Thanks Bob, i think i might have to breakdown and get the puck with hs. The cost just keeps adding up.

[LowePro]

So.....would you guys recommend getting auto chart live?