| LIDAR mapping is a new method used for | | | | and location may be correlated. For this reason, |
| mapping and surveying. This three-dimensional | | | | GPA instruments are mounted on the aircraft |
| mapping system is very popular for engineers, | | | | along with the LIDAR. |
| planners, mapping technicians, GIS professionals, | | | | The data itself is stored in a file with three |
| and surveyors. Compared to similar methods for | | | | coordinates, "x,y,z." X refers to longitude, Y to |
| three-dimensional information gathering, it is very | | | | latitude, and Z to elevation. Once the data has |
| accurate, relatively fast, and cost-effective. | | | | been collected by the aircraft, it is processed into |
| LIDAR mapping is used for topographic surveys | | | | a computerized layout of the land known as a |
| and related applications. | | | | digital elevation model, or DEM. The digital elevation |
| LIDAR stands for Light Detection and Ranging. For | | | | model can automatically draw contours, or lines |
| a LIDAR-created map, topographic data is | | | | connecting points with the same elevation. These |
| collected using aircraft-mounted lasers. The lasers | | | | contours show at a glance whether the terrain is |
| send several thousand pulses per second, and can | | | | relatively steep or relatively flat, an essential piece |
| usually measure elevation changes within six | | | | of knowledge if you're considering building on the |
| inches. By measuring the time delay from sending | | | | land. This map includes evidence of man made |
| the laser pulse and detection of the reflected | | | | features like roads and natural features like lakes |
| signal, LIDAR can measure how far the airplane is | | | | and hills. However, because these are shown on |
| from the ground with considerable accuracy. | | | | the map by elevation only, determining the nature |
| These laser devices are pointed straight | | | | of these features may require aerial photography |
| downward, detecting the aircraft's elevation from | | | | or an actual site visit. |
| the ground directly underneath it as well as slightly | | | | LIDAR mapping is unobtrusive, and does not |
| to the left and right, covering a fairly wide section | | | | require setting foot on the terrain being measured. |
| of land on each pass. Typically, the laser can | | | | This is advantageous in situations where there is |
| collect information over a strip measuring about | | | | limited access to the land from the ground, or |
| 1000 feet wide from an altitude of 2000 feet. | | | | where the terrain is dangerous. Examples include |
| It is possible to cover nearly 400 square miles in | | | | very steep slopes or large mud flats, or areas |
| one 12 hour surveying session, with millions of | | | | where too many trees make surveying from the |
| individual elevation reference points. Compared to | | | | ground difficult. |
| traditional surveying methods, this LIDAR-based | | | | LIDAR is often used to map archaeological |
| 3D map can be made much faster. In fact, | | | | features to create maps of features that may |
| LIDAR contour mapping has already nearly | | | | not be readily apparent from the ground. LIDAR |
| replaced traditional methods. It is many times | | | | can also penetrate groundcover and forest |
| faster than using a surveying station or electronic | | | | canopy, making it ideal for heavily forested sites. |
| version of the old surveyor's transit tool, or other | | | | LIDAR is often used to track topographic changes |
| low-tech surveying methods. | | | | along shorelines. Its uses in construction and |
| Because LIDAR instruments only collect data | | | | building trades are wide-ranging, including the |
| about elevation, these tools must be used in | | | | planning of construction project, highways, and |
| conjunction with GPS devices so that elevation | | | | mines, and the creating of flood plain models. |