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Practical use of geokosmos real-time cartography technologies based on Optech's airborne laser terrain mapping system 2.0 Overview of geokosmos Geokosmos is a privately owned and operated based in Moscow topographical and surveying company established in 1993 in Moscow. The company is reputed to be a significant player in the Russian topographic and geodetic survey market, making use of digital land and aerial surveying technologies as well as 3D digital multipurpose modelling. Geokosmos company focuses on three main lines of business: the provision of professional surveying services using laser scanning technologies, development of its own software products for various surveying applications and consulting and development of integrated laser scanning technologies. In 2001 Geokosmos company successfully carried out the first Russian large scale project involving the use of an aerial laser scanner for large-topographic survey and creation of a 3D digital area model of over 340sq km for a railway design based on the scanning results. It continued studying ground-based scanning systems, actively co-operating with producers and users, and a successful record in the use of these technologies resulted in further projects. The company has at its disposal two aerial laser scanners: Optech’s ALTM-2050 & ALTM-3070 with 50 and 70kHz scanning frequencies and a significant number of Trimble GPS receivers, ProXR, tacheometers and ground-based laser scanners. The company employs a full-time staff of more then ninety specialists: highly technical, creative, young personnel within a strongly organised structure. In October 2002 an aerial surveying division was established. The new division is fully staffed with highly qualified graduate specialists having extensive experience and an impressive record in the application of airborne laser scanning systems both within Russia an in many other European and Latin American countries. Aerial laser scanning has since become a key line in company activity. At present Geokosmos counts among its clients major Russian companies such as OAO Gazprom, RAO ES, MOSAVTODOR and many others. Each of these is ranked high in its respective area. OAO Gazprom holds a huge monopoly in the Russian gas industry, which provides 25 per cent of the national income. All Russian energy resources belong to RAO ES, the biggest Russian power-engineering company, which owns more than 370,000km of power lines.  Fig. 2 Simultaneous recording of ALTM laser data and aerial imagery. The complete processing of both data sets, in particular automatic photo rectification, is carried out by Geokosmos software packages. 3.0 The concept of real - time mapping LiDAR technology has today completely proven its effectiveness. Application like Digital Terrain Model (DTM) production and power-line corridor mapping are already classical. The technology is still progressing, its main advantage first of all lies in its combination with other airborne remote sensing data, such as aerial photography. The immanent ‘3D nature’ of laser data allows fully, automatic spatial orientation, orthorectification and geopositioning of imagery. It is obvious from practical perspective that the simultaneous recording and combined processing of LiDAR data, aerial imagery and some other kinds of remote sensing data accelerate the processing cycle and increase data accuracy and reliability. Such an approach encapsulates the concept of real-time mapping. High priority for both Optech and Geokosmos remains its focus upon the development and implementation of systems and software for geodetic mapping in real-time. The management of both companies believes that a fundamental reduction (of up to a few days or even hours) in duration of the technological cycle of a survey, in particular for aerial survey, has allowed the company to make its image more attractive for potential customers and investors. These have been traditionally used to long mapping processes in Russia. An extremely high level of efficiency, along with the highest quality of data provided, create, among other factors, a very favourable climate in customer relations. The customer is given the opportunity throughout the entire technological process to monitor quality and completeness of data and even to make adjustments to the operation plan. 3.1 Theoretical aspects The progress in LiDAR technology and its numerous topographical application are rather impressive for the last few years. On the one hand the development of sophisticated algorithms for geomorphological analysis is still ongoing, enabling improved recognition and detailed description of objects. On the other hand, fusion with other datasets results in augmented information. In this respect, LiDAR and digital imagery data perfectly supplemented each other. LiDAR allows the effective generation of a DTM while enabling automatic recognition of many classes of objects having a clear geomorphological structure. Digital imagery provides the most natural kind of scene representation, including complete information concerning surface texture. In some cases, this pure visual information may be supplemented with infrared or multi-spectral data. LiDAR data and appropriate processing technology enable the following:
Generally speaking from practical point of view the concept of real-time mapping proposed by Optech and Geokosmos may be regarded to be some alternative for a classical stereotopographical method in cartography. Though it would be more accurate to declare that this technology is derived from wide variety of classical geodetic and photogrammetry methods. It is well known about numerous particular limitations of the stereotopographical method. These are studied in detail therefore it is no sense in thorough description here. Let us just mention the following: The problems of such nature are quite diverse in their characters, but they all are in general tied with issue of points correlation on stereopair. In certain cases this leads to complete inapplicability of the method, for instance in snowed or sanded landscapes with a full absence of visual texture. In other cases this problem puts the results' quality in dependence on the number of the factors like average forest elevation and density when surveying forestry, or buildings shape when mapping city landscapes. The mentioned above limitation of the stereophotogrammetry method emerges mostly in the most practically meaning applications connected with survey of complex and full of objects scenes. Particularly due to this reason, large-scale mapping of city landscapes with significant share of multilevel buildings can not be done by exclusively aerial survey methods, thus forcing massive involvement for this goal carrying out of on-ground topographic survey, extremely expensive in city conditions. Besides, there are season limitations restricting aerial surveys in presence of significant snow cover or vegetation with leaves. For most part of the Russian Federation for example such limitations only leave 1.5 – 2 months a year for aerial survey. Practically, such problems often lead to the serious deformation of technology that causes doubts about results correctness. Thus, production of DTM of a big city area considered as compulsory within the stereotopography method, is deemed such a labor consuming and expensive task affecting the overall cost of project that a 'compromise' is offered to use a relief model taken from existing topographic map of appropriate scale. Given the extremely low metrologic quality of existing topography basis in Russia, it is only left to guess what consequences in future would be caused by such decisions when doing, for example, a cadastre system to regulate real estate relations. It would be reasonable to note here that the main value of the real time mapping technology is that it is next to free from all the limitations mentioned above. This explains its great attractiveness for potential customers engaged in various kinds of topographic activity. The proposed digital technology of mapping in real time has overcome the major disadvantages of the classical stereotopography method which as already mentioned are a necessity of on-ground geodetic support, inevitable manual labour on stages of frames mutual orientation, DTM production and correct combination of orthorectified photos.  Fig. 3 The stages of topography map production under Optech & geokosmos technology of real time mapping. |