How was the impervious data collected?
Impervious features, including pavement, parking lots, driveways, and buildings were also mapped by Sanborn as part of the VBMP in 2009. The features were hand-digitized from the 2009 one-foot resolution orthophotos, and include structures with roofs and paved/concrete surfaces having an area coverage of 200 square feet or greater.

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1. How was the aerial imagery collected?
2. What is orthophotography?
3. How was the impervious data collected?
4. What if my home or building was built or significantly changed after 2009?
5. Why does the impervious layer not exactly match up with the imagery layer?