What are heightmaps?

In principle, heightmaps are just images. However, they are special in two ways:

  • the images are usually GeoTIFFs, so that every pixel is georeference, i.e. can be mapped to a precise location on earth

  • the images are usually grayscale, because the value of each pixel signifies the height of that location's ground above a height reference (like e.g. the WGS84 ellipsoid)

SpatialExplorer's MissionGuidance can use these heightmaps for two different purposes:

  • For an accurate ground visualization in AglOracle

  • To recompute flightlines' altitudes before using them in MissionGuidance

How to retrieve heightmaps

In order to download the right heightmaps for your project, go to https://grids.phoenixlidar.com. Use the "Filter by grid type" button to select only the SRTM 3 arcsecond dataset, then navigate to the project area. Select all tiles that are covered by your project and download them.

The files need to be placed in your Documents\Phoenix LiDAR Systems\HeightMaps folder (this folder is created automatically on SpatialExplorer's first startup). If you have downloaded zipped versions of the heightmaps, please extract the TIF files manually into the same folder.

Above is an example of a flightplan created using 3rdparty software. Sometimes these flightlines will not follow the terrain accurately, or may contain large steps/discontinuities in height. In other cases, the 3rdparty software may not have exported height at all, or using an incorrect datum. In these cases, use the functionality shown above to "reflow" the flightplan above the terrain before flying the project. Be aware that reflowing of flightlines does not add waypoints to flightlines even when extreme changes in terrain height may require it.