Path Profiles

The accuracy of the LINKPlanner results depends upon obtaining accurate path data. This data is a combination of terrain height and the obstructions above ground (e.g. trees and buildings), which is generally known as “clutter”.

Terrain Data

NASA has provided 1 arc second data (30m) covering land masses between latitudes 60 north and 60 south. The vertical accuracy is claimed by NASA to be 10 meters RMS. (See SRTM Technical Guide). LINKPlanner also imports from other data sources to cover the areas above latitude 60 north and below 60 south and other areas not covered by the 1 arc second data.

LINKPlanner uses the following terrain data sources:

Note that the SRTM and ASTER data collection methods generally map the top of the landscape including its land cover, which means that significant areas of land cover such as forest and urban areas may be incorporated into the terrain height. The SRTM data collection happened in February, a period of minimum leaf cover for northern latitude deciduous forests. This needs to be considered when setting the heights for each of the clutter classes for a given area.

Clutter Data

Various databases for ground cover are available in different parts of the world. The creation of these datasets is driven primarily from understanding the vegetation usage across the area and hence the classifications for different types of buildings does vary significantly. The resolution also varies from 30m, which matches the terrain data, to 300m. Adding clutter to the path profiles can be very useful to gain a better understanding of likely areas where the path may impinge on the Fresnel zone, however it may not be suitable in all cases, in which case it can be disabled by unticking the Use clutter? option in Project Properties, see Project Properties

LINKPlanner uses the following clutter data sources:

Profile Accuracy

Even with accurate path data, the losses over certain objects depend upon the curvature of the top of those objects. Nevertheless the tool gives a good idea of the performance to be expected, and by doing a what/if analysis, helps the user to understand the concept of non-line-of-sight.