![]() It won't take a lot of modification to the steps above to do related calculations, such as calculating kWh/sq m values for each cell, and then get mean and/or median values of all cells within a polygon using the Zonal Statistics tool. Scientific/Engineering Data Visualization Quantum GIS Quantum GIS Status: Beta Brought to you by: gsherman, timlinux Summary Files Reviews Support News Donate Mailing Lists CVS NOTE - All project resources are now hosted at Quantum GIS (QGIS) is a Geographic Information System (GIS). If you want particular areas of the roof, you will need to have smaller polygons. This will give you kWh potential per roof. ![]() You should end up with a vector layer where each polygon has an attribute representing the sum of all the raster cells intersecting the polygon. Check the boxes you want for each roof polygon, most importantly the "sum". SCP-001, also known as Awaiting De-classification and Top Secret, is a mysterious name given. 3.4 LTR), which may contain description of features in newer releases (3.2 and 3.4). Introduction to GIS using Quantum GIS 1.8.0-Lisboa. Im totally new in QGIS and especially, in classification. Using the new raster and your building polygons, run the Zonal Statistics tool in the QGIS Raster menu. 'Documentation is versioned and translated only for QGIS Long Term Releases (LTR), meaning that if you are running a regular release (eg, QGIS 3.0), the help button will by default open the next LTR manual page (ie. There is also a raster calculator in SAGA (available in QGIS Processing Toolbox) if you prefer it. You can then use the raster calculator in QGIS raster menu to create a raster where each cell has its kWh potential (the "/sq m" part of the noted "kWh/sq m" units is now represented by the cell size). If each cell is 0.1 sq m, don't forget to divide by 10 (or appropriate conversion based on cell size). Then figure out the math to calculate kWh per cell. If you are in the U.S., a state plane system may work, or else a UTM system could be appropriate anywhere.ĭetermine the units on the raster cell values. Units are in meters, but they are distorted as you move toward the poles. Pseudo-Mercator EPSG 3857 used by Google, OSM, websites, etc. Make sure you are working in a projection with appropriate units. ![]() If you need something finer, perhaps 0.316 m x 0.316 m would work to give you an area of ~0.1 square meters. It may be easier to do the math using a 1m x 1m raster size so each cell is 1 square meter, assuming this isn't too coarse for your evaluation. Generate the raster, as you have done (don't necessarily need to clip to polygons yet if you don't want to). I've not used the PV tool and don't know the units on the raster, but can give you a general idea for one way to accomplish this. ![]()
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