garmin navionics +/vision

[Hookup1]

anybody know what those patterns are on relief shading they start to show up at around 600ft

View attachment 35991

Those "tracks" that you see offshore are from the bottom mapping scans. They mapped high resolution tracks over earlier low resolution map. This added more detail to interesting bottom areas - like where a Russian sub might hide! Inshore areas are mapped differently - not sure how it's done.

The shaded relief maps are raster maps (images). If you zoom in to say 200' scale on any device you will see exactly the same detail regardless of device screen resolution. What is different is the "frame" around the spot will be larger or smaller. Take a look at these iPhone, iPad and 8612 screen shots.



If you zoom in on any of the shaded relied charts on any of the devices they will "pixellate" the raster image. Fishing and navigation charts are vector charts. You can zoom smoothly to any scale.



Fishing and navigation charts will behave the same way with different resolution devices. At 200' scale you will see more or less around you depending on the device. This makes a big difference when you need detail and to see a larger area at the same time. More resolution (not screen size) does make a difference.

 

[SkunkBoat]

Interesting thing about the relief maps. Here in NJ last year there were a lot of those hi res scan tracks added. It looked like they probably came from the offshore wind surveys because thats where they were. They tow a sonar array that scans a wide swath much like your sidescan. They methodically covered wide areas.
I was just looking at it again and now those areas have been somewhat "smoothed" so they make more sense. There is probably some algorithm that averages data in some uniform plan.
They update these things a lot, at least here off NJ. When I first got it, much of the bottom out past 10-15 miles was just matching the NOAA chart depths. It lacked any detail. Now the entire Mud Hole is detailed. Wrecks I could never find are right there...

Here the lower part is detailed. Then some smooth undetailed bottom then some new tracks. In the upper right corner you can see some objects that they were looking for