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Terrain Avoidance Quick Guide#

There's already quite a long article on mwp's terrain analysis tool; this is a quick summary of how to use it in three steps.

1. Load your mission#

First load (or create) the mission in mwp. Here, the pilot chooses to take a cruise around the lake and adjacent country side. The brown / grey icon at the top of the mission is the planned home location. At first glance, the terrain looks quite benign.

Lake Mission

2. Set your avoidance parameters#

By right clicking on any waypoint, we can select Terrain Analysis. No internet connection is required if you already have cached imagery and DEM tiles.

  • Home is taken from the planned home location
  • The pilot elects for 30m clearance above terrain
  • Uses the same altitude definition (Relative / Absolute) as is set in the extant mission
  • Replace the mission altitudes with the altitudes generated from the analysis
  • Highlight any extreme climb / dive angles

Analysis Settings

On clicking Apply, the analysis will run.

3. Review the output#

The output is displayed as a chart of the terrain (green), the original mission (red), the avoidance margin (blue, 30m in this example), and the adjusted mission (orange). There is also a Climb / Dive analysis.

Analysis Result

There are a few places that could benefit from further manual adjustment, but in general it looks pretty good.

  • We could eliminate the unnecessary small dips at WP37, WP41 and WP43
  • It is unlikely we'll try the extreme climb from HOME to WP1; the mission will probably be invoked some distance from home.

So it looks good. Or does it?

Terrain may not be the only hazard#

The terrain analysis is only as good as the terrain data. If we zoom in closely, or look at a difference map source (e.g. OpenTopo), or examine the route in 3D (Google Earth) via flightlog2kml / mission2kml, maybe from fl2xui we can see another hazard. Between WP36-WP37 and WP47-WP48 there are high voltage overhead transmission lines. Hitting these, or at WP48, the tower would be sub-optimal.

Wire alert Tower alert

A re-plan seems like a good idea, at least adding significant altitude on these legs of the mission.