[jmguerreroh]

navmap_tools: DEM files, Gazebo terrain, big point clouds; RViz colours

What the BigMap maps manager (easynav_bigmap_maps_manager, easynav_plugins) needs to get its map
outdoors, and the tools used to make its maps.

navmap_gis_tool

• --dem-out FILE: the DEM of a place as a binary grid file (geo/dem_file.py: header with the
  origin, the reference altitude, the resolution and the source), which the maps manager reads.
  --dem-data-resolution samples the source at its own spacing and interpolates it bicubically;
  --dem-source ign | copernicus30 | mesh | synthetic (geo/ign.py: IGN MDT, Spain, 5 m;
  geo/mesh_dem.py: a DEM rasterised from a mesh, e.g. the collision mesh of a Gazebo world). A DEM
  made with the same configuration is reused.
• Gazebo terrain (geo/terrain_export.py): --terrain-out + --world-template /
  --world-out write the terrain mesh (collision STL, textured OBJ) and a world from a template
  (@latitude@, @longitude@, @elevation@, @TERRAIN_DIR@).
• Vectorised sampling (sample_array) of the Copernicus grid, the tile mosaic and the PNOA
  orthophoto, which the DEM and terrain export sample over whole grids.

pointcloud_to_navmap

Streams ascii/binary PCD files block by block and reduces clouds above 5 M points by voxel
(pcd_stream, voxel_cloud), so memory follows the extent of the map and not the number of points;
several --input; --fill-holes closes the holes a SLAM cloud leaves in its floors
(floor_holes); --min-surface-area, --max-surfaces; colour from the cloud's rgb; it says
which resolution the data holds. The meshing is navmap_ros::from_points.

navmap_rviz_plugin

NavMapDisplay packed the vertex colours as ARGB whatever the render system: with OpenGL (ABGR)
red and blue were swapped. It now uses the render system's own colour format.

Tests

colcon test --packages-select navmap_tools: new tests for the DEM file (round trip, a golden
file, the headers the C++ reader of the maps manager refuses), the IGN and mesh sources, the reuse
of a DEM made with the same configuration, the terrain export and the C++ cloud tools: 562 tests,
no failures.

Independent of the navmap_core / navmap_ros PR (DistanceField, set_area, operator=, navmap_io);
neither needs the other.