Light Detection and Ranging (Lidar) is a method of producing extremely dense collections of 3D points. Lidar data are generated by capturing return signals from emitted light pulses. A pulse can produce several such return signals, each of which is captured as a point in the lidar file.
The lidar data showcased on this site comes primarily from airplane fly-overs. The raw data is post-processed to produce several per-point attributes, including the elevation of the point above sea level (stored as the z-coordinate of each point), the pulse return intensity, and several others. Further post-processing – typically involving integration of other data such as orthorectified photogrammetry – allows additional per-point information to be stored such as RGB color and classification codes. The latter are used to label points as belonging to buildings, bare earth, vegetation, water, etc.
The data set can be displayed simply by drawing the points in the point cloud with colors determined based on one or more of the attributes described above. The collection of programs described here reads lidar data in the LAS format as defined by the American Society for Photogrammetry & Remote Sensing (ASPRS), displays them, and allows them to be edited in various ways. In addition, the point cloud data can be used to create high-resolution elevation models and can be displayed georeferenced on a virtual globe using NASA World Wind.
Two ongoing collaborations have made the tools delivered and documented on this site possible. First, the support of the NASA World Wind project team – and in particular Tom Gaskins and Patrick Hogan – has been of incalculable benefit. None of this would ever have even started had it not been for their support and encouragement.
Second, it is impossible to develop good software without good users providing real data and real application needs. The City of Springfield, Oregon has been such a partner. Brandt Melick and Chris Zeitner have provided extremely valuable input on the needs of urban planning, they have used and critiqued earlier versions of these tools, and they have shared really useful data sets, not only with me to use during development, but also to share with users everywhere.
Under Active Development…
Please note that this software as well as the web pages that describe it here are both under active development. Every attempt is made to keep the written descriptions in sync with the software, however the screen shots you will see on these pages may not always reflect the latest version of the software, especially when differences do not materially affect the information being conveyed.