Some data is derived from remote platforms like satellites, small planes, and helicopters. Satellite imagery is typically of a lower resolution and is suitable only for large scale applications. In a statewide, countywide, or municipal environment, it is not uncommon to utilize digital aerial photography with a resolution of as little as three inches—that is each pixel or dot in the image represents an area on the ground three inches by three inches in size. All imagery can be obtained in either grayscale or color format.
A relatively new technology that is used for deriving elevation data is Light Detection and Ranging (LiDAR). LiDAR systems utilize aerial mounted lasers that fire at between 30khz and 200khz (30,000 to 200,000 times per second). The laser bounces off the first thing it hits and the reflection is detected by a sensor on the plane. The time it takes for the light pulse to travel from the plane to the object below and back determines the distance between the plane and the object. The plane is equipped with precise navigation equipment that tracks the location and elevation of the laser, from which the elevation of the ground can be determined with remarkable precision. From this imagery and LiDAR data, Spatial Systems can derive locations of visible items and elevation data accurate enough to allow us to produce one foot contours to national map accuracy standards.
Spatial Systems assists our clients in writing the specifications for the acquisition, procuring, and subcontracting for this data; provides processing of the resultant data and development of deliverables, performs QA/QC services on the data, and delivers final workproduct to our client.