Tag Archive: Georeferencing services

ROAD MAPPING USING MOBILE LIDAR APPLICATION

3

Management of road networks and its associated assets is a huge task for all transportation agencies around the world. The traditional ways of collection of data was time consuming and the productivity of the staff was at the best average. With the advent of new technologies like Mobile LiDAR Mapping, the collection, assimilation, analysis, design, construct, maintain and storage of data has become very fast, accurate and cost sensitive This dynamic system of mensuration can be used to acquire highly accurate and compact 3D statistics by safely driving a gathering vehicle at public road speeds

Mobile Lidar systems is made up of of four different devices: a laser, a scanner, a photodetector and a GPS/IMU positioning system. These four systems assimilate to measure the distance to an object by lighting the target with throbs of light from the laser instrument and gauging the time it takes for each throb to bounce back to the sensor. For the reason that light moves at a persistent and known speed, the distance between the laser instrument and an entity can be measured with a high degree of accuracy. A briskly firing laser can cover entire scenes in a few strokes, visualizing the topography and extracting data. A highly capable processing software then transforms raw data into colorful 3-D point clouds, and the end results are multifaceted, high-resolution maps.

Collection of detailed, high accuracy street-level data of street framework is expedited by having instruments capable of reading GPS/IMU on a automobile platform, achieving immense extents of GIS-friendly LiDAR point cloud data in short amount of time. Terrestrial LiDAR system is competent to see data flanked by buildings and under tree canopy, which airborne systems, will never be able to capture. Mobile mapping systems usually collect a full 360-degree FOV at a speed of 30-40 kilometers per hour. The data collected will be highly precise and can be used to generate convincing 3D data and highly accurate road maps.

2

Geo-referencing factor of mobile mapping is akin in idea to airborne platforms, but distinctive in run through. It is not possible to keep the GPS lock all the way through an entire mobile survey. The mobile platform must be able to traverse, and accurately map, below tree canopy, under bridges, without loss of positional accuracy. The IMU system become judgmentally important. The airborne system necessities for GPS/IMU quality basically do not apply in these situations.

As is the case with every mapping application, supplementary imagery and substantial data post-processing is often crucial to producing GIS or CAD-compatible final products. The processing applications necessitate solid surfaces with unambiguously defined edges, and topologically-structured feature objects (points, lines, and polygons) with widespread data description and attribution. The time and effort involved in taking out these features from LiDAR point clouds has been a process only knowledgeable persons can work out. This needs special LiDAR/Point cloud processing software and custom data formats, as is for airborne or fixed systems, transfers over to mobile systems and is augmented by the steep quantity and intricacy of the data acquired.

Incorporation of mobile mapping data, generating exhaustive data for highways and metropolitan infrastructure) with mobile topographic LiDAR survey generated terrain models and oblique imagery is sure to turn into the gold standard for street mapping and visualization in the very near future.

Geo referencing Service

SBL through its varied geospatial services is in forefront to full fill the requirements of all of its clients. Georeferencing is one such service SBL provides. Georeferencing means bringing maps and images in to a real world coordinate system. Satellite and other kinds of images and scanned maps are devoid of any coordinate information in its raw form and hence cannot used for any of the geospatial purpose. Some of the satellite images are loosely georeferenced when it is procured. Here also positional accuracy is a big issue. So georeferencing is the primary pre requisite for the creation of any kind of geospatial data base creation. For scanned maps georeferencing means bringing to the geospatial frame work. For satellite images georeferencing means applying geometric correction to the images. Assigning a suitable project is always an associated activity in georeferencing. So georeferencing is not only bringing the maps and images to the coordinate framework, it also involves with assigning a suitable projection so that maps and images will be of real world coordinates. A georeferenced map or image will open in its correct spatial location and can be used with similar other georeferenced maps for various overlay analysis. Hence georeferencing is a positional correction applied in x, y direction of the maps and images. Orthorectification is a refined form of georeferencing where relief displacement will also be taken care so that images will be correct with respect to x, y and z planes.

Georeferencing is a basic function available in almost all geospatial software platforms. The major activities involved are incorporation of ground control points, re projection and re sampling. Ground control points are those points whose coordinate information (latitude and longitude values) were known prior hand and is identifiable in maps and images. Ground control points can be taken from printed graticule values on maps, or can be surveyed using precision instruments such as DGPS and can be taken from a pre geo referenced map or image. A minimum number of 5 GCP values are required for georeferencing. Based on the accuracy requirement number of GCPs and type of GCPs can be determined. Once the ground control points are placed, using the software algorithms we can re project and re sample the maps or images. Various complex statistical methods and transformational equations were used for the re sampling the images to its real world coordinates. During the process each and every pixel of the maps and images will be re positioned with respect to the GCP and methods used for the purpose and finally a georeferenced maps or image can be generated. Accuracy of the georeferencing can always be obtained through RMSE error for the GCPs used in the process. Hence it is very much a quality controlled activity where very high positional accuracy can be obtained. SBL is capable of handling images and maps in huge numbers for geo referencing and allied acidities.

georefercing-new-img

Georeferencing services

Georeferencing services