The impervious cover data was generated using two different aerial photography and LiDAR data, collected in January 2012. The data was used to create impervious cover maps seen on the Find My Drainage Charge Map Tool. (For best results, use Internet Explorer 9 or higher, Firefox, Google Chrome or Safari.)
Each pixel on the aerial photography represents 6 inches on the ground. The accuracy is suitable for defining the edges of buildings, patios, driveways and other types of impervious cover.
LiDAR is a remote sensing technology that measures distance by sweeping a laser rapidly across the ground from the bottom of a plane flying low over the earth. The reflected light is gathered as a cloud of three-dimensional points and measured to determine how much light is reflected. Different surface types return a different signature of light. How long it takes the light to reflect from objects on the ground can indicate the height of these objects. LiDAR helped define impervious cover under tree canopies and the edges of buildings.
Updating the Data
Aerial photography for 2015 has already been taken, and a project is currently underway to update the 2012 impervious cover to match the 2015 photography.