Light Detection and Ranging (LiDAR) systems

A visual remote sensing technology used to collect a wide range of topographic data Lidar services (Light Detection And Ranging ) is an contraction for Light Detection And Ranging, sometimes also referred to as Laser Altimetry or Airborne Laser Terrain Mapping (ALTM). The LiDAR system basically consists of addition of three technologies, namely, Inertial Navigation System (INS), LASER, and GPS.The Global Positioning System (GPS) has been fully operational for over a decade, and during this period, the technology has proved its potential in various application areas. Some of the important applications of GPS are crustal deformation studies, vehicle guidance systems, and more recently, in LiDAR.Lidar Data Mapping also known as airborne laser scanning (ALS), is an emerging remote sensing technology with promising potential to assisting mapping, monitoring, and assessment of forest resources. Compared to traditional analog or digital passive optical remote sensing, LIDAR offers tangible advantages, including nearly perfect registration of spatially distributed data and the ability to penetrate the vertical profile of a forest canopy and quantify its structure.

The LiDAR system includes parameters that let the point distribution on the ground to be adjusted. Normally, the parameters are placed to generate a uniform distribution of points for the most applications. The LiDAR can also distinguish intensities of the return, which can then be used to develop a set of data points that resembles a black and white photo. The intensity data can be laid over the height elevation model. Some triangulating of points are performed by the software to give us a quick view of what the processed data looks like, which is why the trees appear as triangles. There are several major components to a LIDAR system Laser, Scanner, Photodetector, Position and navigation systems

Laser scanning technology is changing many aspects of surveying profession today. Possibility to capture huge amount of georeferenced data in a short period of time is raising challenges both to hardware and software. Many industrial facilities lack modern digital documentation needed for effective maintenance an upgrading. Old paper maps and blueprints are usually two-dimensional and based on classical surveying methods.

The bare earth digital elevation models (DEM) are a representation of the earth's surface where all man-made structures and vegetation have been removed.The bare earth DEMs were created from a subset of LiDAR returns that were classified as ground.They are regularly gridded at six-foot post-spacing and were derived using TIN processing of the ground point returns. The elevation values are in feet.The DEM data format is ArcInfo interchange. Terra Point surveyed and created this data for the Puget Sound LiDAR data processing Consortium under contract.

http://www.sblcorp.com/services/geospatial-services/lidar-services/

Digital elevation modeling (DEM)

Digital Elevation Models DEM are data files that include the elevation of the terrain over a specific area, generally at a fixed grid distance over the surface of the earth. The distance connecting each of the grid points will constantly be referenced to some geographical coordinate system. This is usually either latitude-longitude or UTM (Universal Transverse Mercator) coordinate systems. The details of the peaks and valleys in the terrain will be better represented with small grid spacing than when the grid intervals are very large. Elevations at the specific grid point locations are not contained in the file. As a result peak points and valley points not coincident with the grid will not be recorded in the file.











The term Digital Elevation Modeling is often used as a generic term for DSMs and DTMs, only representing height information without any further definition about the surface. A DEM can be represented as a raster (a grid of squares, also known as a height map when representing elevation) or as a vector-based triangular irregular network (TIN). The TIN DEM dataset is also referred to as a primary (measured) DEM, whereas the Raster DEM is referred to as a secondary (computed) DEM. DEMs are commonly built using remote sensing services techniques, but they may also be built from land surveying. DEMs are used often in geographic information systems, and are the most common basis for digitally-produced relief maps. The DEM could be acquired through techniques such as photogrammetry, LiDAR, land surveying, etc. While a DSM may be useful for landscape modeling, city modeling and visualization applications, a Digital Terrain Model is often required for flood or drainage modeling, land-use studies, geological applications, and much more. Methods for obtaining Digital elevation data used to create DEMs such as LIDAR,Stereo photogrammetry from aerial surveys, Block adjustment from optical satellite imagery, Interferometry from radar data, Real Time Kinematic GPS, Topographic maps, Theodolite or total station, Doppler radar, Focus variation .Inertial surveys.









Digital Elevation Models (DEMs) are a type of raster GIS layer. Raster GIS represents the world as a regular arrangement of locations. In a DEM, each cell has a value corresponding to its elevation. The fact that locations are arranged regularly permits the raster GIS to infer many interesting associations among locations. One of the most powerful applications of DEMs is adding synthetic hillshading to maps so that the map reader may see the relationship between terrain and other things you may be mapping.








http://www.sblcorp.com/services/geospatial-services/