Landcover and Vegetation mismatch

[Amerio.Stephane]

Hello,

I'm using a landcover raster in my landscape, and I add vegetation on top of it. The landcover tag is created with a 0 threshold. A terrain detail layer is added on the same tag, shown hereafter with a red overlay. And vegetation is created with an ObjectGrass node. The problem here is I don't understand why the vegetation and the detail layer never match, whatever settings I put in the Mask of the detail layer:

As you can see, there is grass in A but no grass in B. I would have expected the grass area outline to roughly match the red area (at least for a certain combination of threshold, width, contrast) but that is never the case !

Can you help me here? Thanks.

[Amerio.Stephane]

Here is another screencap from high above. (The lod distance of the grass has been significantly increased just for this capture)

[werner.poetzelberger]

Not an expert in that, but it looks like an offset issue for me, comparing the left, right, up, down directions.

[morbid]

Hi!
Thank you for feedback!

This behaviour is caused by low resolution of landcover source (80 meters per pixel).
However, this is a bug and we'd described it in our internal tracker. Fix will come in the future release.

If it's possible, you could try landcover source with higher resolution.

[Amerio.Stephane]

Thanks for the info ! FYI, we do have some hires landcover but for some other data we only have the lores. Maybe we'll have to upscale artifically our lores then.

What would be the recommended resolution (px/m) ?

 

[morbid]

In general - the higher the resolution the better will be result. At the cost of processing time, of course.

To give you more useful answer I need to consult with my colleagues who are busy due to I/ITSEC event. 

[morbid]

Hello,

glad to say that we've implemented an improvement for this case. Will be available in the next release.

Grass still works much better with higher landcover resolutions but you can try doing the following:

• set step for grass equal to landcover resolution (80 in your case)
• adjust Thershold, Width and Contrast in details settings to modify mask shape

Please, take a look at screenshot attached, not perfect but looks better.