If there is something wrong with that rendering if the area there could be hundreds of mariners who might discover the problem with their keel before you do with yours. There is also something to be said for the “testing” that occurs when every mariner transiting an area using raster charts winds up looking at the exact same image representing the environment. But there is no blue indicating shallow water even though the surrounding 20’+ areas are blue. You can see the waypoint is right on the 8.9′ indicator. Using the Navionics data of the area zoomed in the shallowest area (9′ of water) is (erroneously?) white, indicating safe water. 164′ ought to be no problem, right? But, if you zoom in enough using the NOAA data Navionics renders this as a danger area: NOAA Data Zoomed In Using the NOAA or Navionics (pay) data zoomed out it looks like hundreds of feet of water: NOAA Data Zoomed Out Navionics Data Zoomed Outīoth contours show 164′. I can’t get George’s Shoal to show up in Navionics while zoomed out for the life of me.
The raster charts are clear: they either show you the area to be avoided clearly or indicate that they’re not showing you detail at the level you’re looking at. On a boat that draws 10′ this giant 1.5 fathom area is to be avoided. Let’s keep zooming in: Raster Zoom 3 Raster Zoom 2 Raster Zoom 1 Raster Zoomed way inĪnd now we can clearly see that we’ve zoomed too far in. There it is! In a chart showing thousands of miles you can see there is an obstruction. So we try zooming in a bit: Raster Zoom 4 It’s obvious that we simply don’t have data at this scale. This is what George’s Shoal looks like on the raster charts from all the way zoomed out to all the way in using MxMariner: Raster Zoomed way out Some of the boats I sail aboard could run aground there. George’s ShoalĪn example closer to home is George’s shoal 100nm East of Cape Cod. Next I’ll show you the kind of misrepresentations I’ve come to expect from vector charts.
Raster vs vector how to#
A small scale raster chart of that area would clearly mark the area as “danger” and if one were to zoom in the picture would immediately look wrong as raster chart software doesn’t know how to draw a chart at all, let alone approximate one using insufficient data.īut they were using software I can’t afford and charts I don’t have to compare.
Vestas’ vector chart software didn’t have the data downloaded necessary to enable safe navigation but it probably drew a picture that said “insufficient data” in small print and generated what looked like the chart of areas where it had sufficient data.
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