2D map from Octomap

edit

Thanks Felix,

Found another way around it in the end, though possibly less efficient than your approach. The first thing I found out was that octomap server accepts min and max z values just as parameters so by adding

param name="occupancy_min_z" value="-0.5"

param name="occupancy_max_z" value="0.5"

to the launch file I got a cut down octomap, which then gave a sensible 2d map. Quite nice having the 3D map as well though, for visualisation if nothing else and I'd rather not run 2 octomap_servers, so I had a look through OctomapServer.cpp and edited the 2d map stuff so that it only adds to the occupancy grid if the point is within a certain z range:

void OctomapServer::handleOccupiedNode(const OcTreeROS::OcTreeType::iterator& it){
// update 2D map (occupied always overrides):
if (m_publish2DMap){
  ...........
octomap::point3d curpoint;
  m_octoMap->octree.genCoords(nKey, m_treeDepth, curpoint);
if (curpoint.z() > -0.5 && curpoint.z() < 0.5){
    m_gridmap.data[m_gridmap.info.width*j + i] = 100;
}
  } else{ ..........///same thing here