High Accuracy DTM Editing and Orthophoto of a Mining Area Using UAV Imagery

Abstract: This project was executed by SBL for a mining company having operations in Africa. The study area covered approximately 32 sq.km of land falling in the south western part of Congo.This project was awarded to SBL based on the excellent quality and timeliness shown during an earlier project for Landuse and Landcover mapping. The client requirement was for the creation of hight accuracy DTM edited to 0.2m, DSM of 0.2m and orthophotos of 10cm GSD using UAV imagery

Client: Client is a mining company based in the UK and having mining operations in various parts of African continent

Geography: ~32 sq.km of land falling in the south western part of Congo
Industry: Mining .

Challenges:
• GCP distribution was not even and so getting a good quality stereo model became difficult. So SBL’s experts suggested suitable areas for collecting additional GCP’s which proved to be very useful in the end.
• Fixing the terrain height and water body was a challenge as the area is a dense forest with large swathes of swampy land.
• Data being of 0.2m handling and viewing it was difficult.
• Editing 0.2m DTM was a very big challenge.

Approach: SBL used state of the art UAV softwares in carrying out the Aerial Triangulation of the UAV images. After Point cloud densification and DSM creation Undistorted images were generated by the UAV software after the creation of DSM data. The Aerial Triangulation reports were imported into Inpho Match AT and stereo models were created in it. After this DTM were generated and edited using Inpho DT Master software. SBL’s highly experienced professionals produced high accuracy DTM by the correct usage of soft and hard breaklines . All manmade structures and vegetated areas were interpolated to terrain height after plotting breaklines which were fixed to terrain heights. The edited DTM points were exported in XYZ format and edge matched with adjacent DTM tiles and dispatched to the client.


Benefits: The client benefited by this work in
• Getting high accuracy DTM’s of 0.2m by the use of cutting edge UAV softwares.
• Very quick turnaround time.
• Use of photogrammetry software along with UAV software helped in getting a good DTM output.

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

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/

Geographical Information System (GIS)

In this era of information and technological advancements, data is on our fingertips as we have no time to waste to access the most reliable data and we get instant access to information through internet and other media. Geographic Information System (GIS) enables easy and quick access to various kinds of data to professionals, researchers, administrators and the general public. Enhanced paper records in association with GIS services increases the effectiveness and efficiency which results in higher levels of data authenticity.

When Dubuisson coined the term Geomatics in 1969 merging the terms geodesy and geoinformatics, he intended to use the techniques in remote sensing, land survey, cartography or geospatial mapping, GIS, GPS, photogrammetry, geography and all the related forms of mapping the earth in general.

Geographical Information System (GIS) is an emergent tool in the present day environment which has the prowess in organizing complex spatial attributes in distinct tabular relation. This powerful information system is used to develop accurate and convenient digital spatial database which includes the derived data sets from very precise navigational and imaging satellites or aircrafts, from the digitization of maps and other transactional databases.  Our limited mental calculations cannot restrict the absolute potential of GIS. 

In the recent years, there has been a growing demand for the storage, analysis and showcasing of complex and enormous data to be incorporated in the Geographic Information System. This leads in efficient handling of massive data and also for the analysis and transfer of geographic information across the globe. In the present time, there are many geospatial networks which share geospatial data sets with data linked to specific geographical references.

                                                      geospatial mapping

The visible and sudden growth and of GIS services  in the 20th century has been brought up by the innovative upsurge in the technological realms, computer hardware and software,  advancements in computer science and engineering along with the potential rise of  latest remote sensing  technologies  in space observation.  In general terms, remote sensing refers to the activities of recording or closely observing and registering or sensing objects or natural events at remote or distant places. Remote sensing can be termed as the science that deals with the derivation of specific information about an object by using sensors without physically contacting the object in observation. Hence we can say that remote sensing differs from in situ sensing of objects without physically touching the objects of measurement. Remote sensing becomes very important branch of GIS services.

Another useful aspect of GIS is Image Georeferencing, which is the process of assigning proper geographic information to a particular image to match a particular size and position. Locating or pinning an image in the world facilitates the determination of the information of the features like location, size and distance of that specific locale. Many GIS services outsourcing companies in India are capable of processing such imagery to multiple levels as per the requirements of the clients.

photogrammetry

 SBL Geomatics, the GIS wing of SBL, which plays a major role in the GIS outsourcing services in India, provides a accurate and customized leading-edge GIS solutions for the retrieval, projection, transformation and analysis of both spatial and non-spatial data which allows the users to manage and manipulate location wise co-ordianates and thematic attributes of data and produce necessary reports and this makes geospatial mapping easier. SBL Geomatics  offers an array of GIS services that helps its clients to benefit in the planning, generatin and dexterous implementation of prospective GIS services.

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