Gridmap intitialization with interpolation

[evenlund]

It appears that Gridmap is using linear interpolation between cells as default. The demo-example shows how to transfer one map to another using interpolators, but is it possible to set a default interpolator when initializing the gridmap?

The example seems quite complicated using a yaml. Would it be possible to do interpolation directly in code?

[maximilianwulf]

Hey @evenlund, check out this function: https://github.com/ANYbotics/grid_map/blob/d9ee02deb5af682339610ad2313c0bd9c052df75/grid_map_demos/src/InterpolationDemo.cpp#L268

You can use the example to craft your solution.

Using yaml should not be complicated, it just sets one variable, check here: https://github.com/ANYbotics/grid_map/blob/d9ee02deb5af682339610ad2313c0bd9c052df75/grid_map_demos/src/InterpolationDemo.cpp#L245

Maybe I didn't get your question, could you elaborate what part is missing?

[evenlund]

It is sort of answering my question. I assume there is no constructor or init function that will set the interpolation used directly when creating the gridmap object, so you would need the original map and a duplicated map that has the interpolation you want.

What confuses me the most with the example is that there is no main function. I understand that this is not a forum, but could you tell me how to "convert" a standard ROS cpp file to one that accepts yaml input? I looked at the ROS wiki for "Parameter Server", but could not find info there.

[maximilianwulf]

It is sort of answering my question. I assume there is no constructor or init function that will set the interpolation used directly when creating the gridmap object, so you would need the original map and a duplicated map that has the interpolation you want.

Yes, I think so.

Here is the main function of the demo.

The yaml file is read in the launch file at this line. From then on all the parameters in the file are available through the rosparam. The usage can be seen in https://github.com/ANYbotics/grid_map/blob/d9ee02deb5af682339610ad2313c0bd9c052df75/grid_map_demos/src/InterpolationDemo.cpp#L268

[evenlund]

I think I got the interpolation working now. Unfortunately it does not change the representation I get of the data.

To explain a bit further I would like to place sensor data onto a flat gridded map similar to a checkered chess board, where each square has uniform color and no interpolation happens between the squares or internally in the square. It is perhaps more comparable to a rasterized image. I sort of obtain this by using a gridmap with flat height transformer, but I am trying to remove the interpolation that happens internally in the square and between the squares (see attachment). If I don't initialize the grid with a value when using "gridmap.add" I see that tiangles appear when data is added to a new position and is not populating the whole square.

• Is it possible to remove internal and external interpolation fully (preferrably on the original grid instead on a new gridmap)? Is there some kind of subgrid in each square?
• The coloring becomes a bit psycadelic to my taste with rainbow and two colors are a bit limiting. Is it possible to use a multi color map like in matplotlib, matlab, paraview and others with grid_map?
• Can you explain some more the difference between the demo variables "groundTruthResolution", "dataResolution", "interpolatedResolution" in reference to these questions?