PLANT DESIGN AND ENERGY PRODUCTION ESTIMATION - Wind Resource Assessment: A Practical Guide to Developing a Wind Project - page 233

These data can be obtained from a variety of sources, some of which are listed in
Appendix B. Data layers can also be created through the digitizing of aerial pho-
tographs or topographic maps. (This may require some GIS expertise and digitizing
equipment.)
It will be useful for the analyst to be familiar with the three types of geographical
and geophysical files that are most often used and with their main purposes.
• Backdrop images are for visual reference only. They help orient the user on
the landscape and make sure all other features are properly aligned (an example
is shown in Figure 16-2). Backdrops can include aerial photographs and topo-
graphical maps, which are often available in a georeferenced format such as
geotiff, or in a standard graphical format (bmp, tif, jpeg) accompanied by a
georeferencing file such as an ESRI ArcInfo “world” file. If no such georef-
erencing information is available, then it may be necessary to create it within
aGIS.
Figure 16-2. Backdrop image from a USGS topographic map, overlaid with point layers show-
ing houses (red squares) and turbines (blue diamonds) and polygon layers showing the project
boundaries. Source: AWS Truepower.