Racking Area and Topography
Boundaries and obstructions can be drawn or modified by the user using the tool pallet in the upper left corner of the screen. The total area, rackable area and % utilized values shown in the bottom left Summary Box will update in real time as changes are made. When an obstruction or ground mount area is selected, it can be named in the site tab on the right hand sidebar and a setback can be specified.
Import Topo
To start topography analysis, select the blue “Get Topography” button in the top right corner. PVSketch Mega will download topographic elevation data from Google’s Elevation Service and create a 3D triangular surface mesh. The Elevation service provides elevation data for locations on the surface of the earth, including depth locations on the ocean floor (which return negative values). In those cases where Google does not possess exact elevation measurements at the precise location you request, the service will interpolate and return an averaged value using the four nearest locations.
Google uses a range of digital elevation model data sources to derive the terrain layer. Throughout the US, it appears that the terrain layer comes from either 10 or 30 m (1/3 arc-second & 1 arc-second respectively) DEMs from the USGS National Elevation Dataset (NED). Globally the terrain data appear to be derived from either Shuttle Radar Topography Mission (SRTM) data or something like the NOAA Global Land One-km Base Elevation Project (GLOBE) dataset. Recently however, We’ve begun to notice bare earth LIDAR data patched into the terrain layer and expect that trend to continue.
Once completed, the screen will automatically split in two, with a 3D model of the terrain shown on the right hand side and an overhead map view on the left hand side. You can use your mouse to rotate and zoom in to the 3D model on the right hand side. It may take several minutes to retrieve the elevation data from Google’s server if the area is large or the internet is slow.
You can toggle between the split screen, map view or 3D view using the controls on the very bottom of the Analysis Tab on the right hand side bar.
Topographic Analysis
Once topography data has been loaded, you can perform a slope analysis. There are five controls in the Analysis tab that are used for this purpose.
“Scale” input will adjust the scale of the 3D model in the Z direction, basically a larger scale value will make hills and valleys look taller and deeper and lower value less so; this is to make it easier for a user to visualize the topography.
“North Slope Threshold” that represents the maximum slope angle that you want to allow in the north direction, note that trackers installed on a northern slope will produce less energy than trackers mounted on flat or south facing slopes. Blue triangles indicate suitable slope tolerances and gray triangles indicate out of spec terrain slopes. Any triangle in the triangular surface mesh that exceeds the angle specified here in the north direction will turn grey to indicate that it is out of spec. Simultaneously, in the left hand map screen, orange obstruction areas will indicate these areas in the map as unsuitable for map. The Summary box will update.
“South Slope Threshold” it is identical to the “North Slope Threshold” except that it applies to the south direction.
“East/West Threshold” which applies to both the east and the west component of slope.
“Minimum Contiguous Area” , this represents the smallest contiguous area that will be considered by software for placing modules in the layout. It can be used to eliminate small islands of rackable area that in practice are too small to use for a real world layout. The rackable area and %utilized values will update in real time as adjustments are made to the slope thresholds and minimum contiguous areas for the project.
