To pre-compute what the RF accessibility of AREDN nodes might be, YAAC can do approximate line-of-sight calculations between nodes in the network to determine which node pairs have a clear line-of-sight between them, based on the ground elevation or terrain, any man-made or natural obstructions (such as buildings) protruding up from the ground, and the above-ground-level (AGL) height of the AREDN nodes above the local ground. YAAC can also calculate the same for proposed new locations of AREDN nodes, both relative to each other and to existing nodes in the network.
To perform the computations, YAAC needs to download all of the OpenStreetMap data in the area between the nodes (including the unlabeled map data such as unnamed buildings) and the Digital Elevation Model of the ground heights (available from the U.S. Geological Survey). This information will be used to estimate possible obstructions between the all the AREDN nodes known to this station (real nodes from the OLSR routing table in your local AREDN node, and proposed nodes defined for prediction purposes).
The View->AREDN Accessibility menu choice opens a window that displays the locations of all the real AREDN nodes, all the proposed nodes that are manually added for prediction purposes, and the usable interconnections between the nodes, based on the terrain and map obstruction data. You can also click on any interconnection cell in the interconnection table to produce a line-of-sight plot between the nodes.