Some new gridmap layers

[estherag]

Hi,

We’ve added some layers to extract traversability information:

First, we created a smooth elevation layer. The images below show the output of the smooth elevation followed by the original elevation:

2. Then, based on the smoothed elevation, we added a slope layer with values ranging between 0 and 1.57 radians:

3. Finally, we discretize the slope into three values to represent traversability. For this, we use a sigmoid function that transitions from near 1 to near 0 as the slope increases past 0.7:

value = 1.0f / (1.0f + std::exp(10.0f * (slope - 0.7f)));

The output is then scaled to a range from 0 to 3, and truncated to an integer between 0 and 2. In practice:

• When the slope is roughly between 0.63 and 0.77, traversability is 1.
• For slope values below ~0.63, traversability is 2.
• For slope values above ~0.77, traversability is 0.

What do you think, especially regarding the traversability function? We could also consider a simpler exponential-based approach like:

value = 3.0f - ((slope - 0.63f) / 0.14f) * 3.0f

to avoid scaling the sigmoid output. However, we believe the sigmoid provides a more powerful and smooth transition.

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Codecov Report

Attention: Patch coverage is 2.41935% with 121 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...av_gridmap_maps_builder/GridmapMapsBuilderNode.cpp	2.41%	117 Missing and 4 partials ⚠️

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[estherag]

Based on our discussion today, we will maintain the base grid map with the elevation layer separately from the application-specific implementation, which will include additional layers as needed. I'll close this PR, thanks!