Hi,
Not sure how to explain this but it seems like some info from the tracks is lost.

The track is from a Lowrance HDS-5 gen1 (works just fine in DrDepth). Track is much bigger (600MB) than the screenshots. The problem appears all over. Just zoomed in to get a good view of the problem.

The track, looks ok i guess


The contour, missing a lot of info. Tried several different settings, all of them more or less bad.


Maybe just a beginners mistake, hope you can help me out

Jim

Hi Jim,
The issue you have with your track is that the data is spaced too far apart to "join up" and form contours. ReefMaster does not extrapolate data around track data, so you don't get much of a map from a single straight section of track. I know that DrDepth (and I think Insight Genesis) do extrapolate a little, so you would see a narrow strip of contours along a track path.

You have a very low Max interpolation setting, which is preventing RM from joining any data that is more than 25m apart. The first thing to try is increasing this value (try going all the way up to 250m) and regenerating the map. You'll probably see quite a lot more filled map, where data is interpolated over the full 250m range. It's hard to say from looking at your track how far the different parts are. It may be that you need to get some more data to fill in those holes.

If you add a shoreline (and assuming that this shoreline is with the Max interpolation distance from track data), then that will act as a source of depth data and will enable your tracks to interpolate towards the shore.

Matt

Not sure thats the case. Tried to set interpolation to 250 m and still gets the "holes". If I shift to raster it seems to work better. Se attached screenshots.

high interpolation dont fill the holes


Raster in stead of vector do fill holes


close zoom of the plotline where vector contours dont show up. " Plotpoints" is quite close.


Jim

Jim,
The issue is that sections of your track are more or less straight. Even though adjacent trackpoints are close enough to each other, the resulting interpolation will not have any area, hence the resulting contoured area is very narrow. How big are the distances indicated by the arrows in the image below? You need to get this below 250m (ideally much less, for a good quality map).

Matt wrote: I have noticed the same in the past but this explanation makes a lot of sense. The areas like turns do fill in some data because they produce small chords. So you either need to zig zag or commit to a second pass.

Thanks Matt,
Just so I get this right, you mean that one single, straight plotline actually will not produce any vectors unless Max interpolation is turned up. If this is the way RM i designed I can understand my results. Look at this example.

The plotline


25 m interpolation results in almost nothing


50m interpolation, line of vector info appears


A straight line resulting in almost nothing unless max interpolation is turned up a bit. I was comparing to another program (DrD) with always makes a narrow continuous vector result from a single plotline. So I figured something was wrong. But maybe this is just a difference in the interpolation algorithm.

Jim

Jim,
In practical terms, max interpolation won't make a lot of difference if all you have is a single straight line. Consider how the track would look if you connected every point to every other point (within max interp) with a straight line. For a straight track, you'll just get a line, and this is the area of the finished map. What you see on DD is (more or less) just the depth of individual positions in the track extrapolated outwards slightly; there is very little extra information there.

What you need are sections of track that run close enough to each other so that values can be interpolated between them, in 2 dimensions. As Dan mentions above, you would also get a larger area by running a zig-zag track, but in general I would suggest that you just run parallel swaths within 50m or so, and then run another set of swaths perpendicular to these. There is no getting away from the fact that, in order to make a useful map, you need to collect a reasonable amount of data and that data cannot be too sparse.

Matt