Manually digitized polygons

Finally, there were situations in which required datasets were either unavailable or lacked the specificity to utilize the previous three methodologies. This generally arose if source datasets had very few observations or there was a complete lack of OSM polygons for a life cycle component. In these cases, we manually digitized spatial footprints using aerial imagery, after which subsequent raster processing followed one of the first two methods (e.g., Fig. 5). For some datasets, sufficient point observations were available and were randomly sampled for manually digitizing footprints. From these samples, linear regressions could be developed and used to estimate buffer radii (as in the second methodology).

Manually Digitized Polygons stepwise process. (a) Point data representing a given energy life cycle are obtained, (b) Polygons are developed using ARCGIS tools and aerial imagery as a reference.