Corridor Survey of Both Existing and New to be Built Pipelines on Land Using LiDAR Scanning

Transcription

1 Corridor Survey of Both Existing and New to be Built Pipelines on Land Using LiDAR Scanning 1. Introduction For good monitoring and planning an onshore pipeline and to feed the Geographic Information System, detailed information regarding the terrain and the topography is needed. This process is called the modelling of the pipeline corridor. Traditional land survey techniques are impractical due to time, costs and above all access issues involved. With remote data collection, these issues no longer present a problem. Fugro Geospatial Services provide a wide range of remote data collection services e.g. satellite imagery analyses, photogrammetric work and aerial Light Detection and Ranging (LiDAR) surveying. FLI-MAP (Fast Laser Imaging and Mapping Airborne Platform) is a laser scanning system which is an in-house development of Fugro offering a solution for those high-demanding topographical surveys of pipeline operators. 1.1 Introduction of Fugro Fugro was founded in 1962 and has been listed on Euronext Amsterdam stock exchange since 1992 and became part of the AEX-index as of September Fugro is a multinational with more than 275 offices and 13,600 employees worldwide and collects and interprets data related to the earth's surface and the soils and rocks beneath and provides advice, for purposes related to the oil and gas industry, the mining industry and the construction industry. Fugro operates around the world at sea, on land and from the air, using professional, highly-specialised staff and advanced technologies and systems. Within the group of Fugro companies a variety of pipeline related services to the oil and gas industry can be offered such as; pipeline survey (on- and offshore) pipeline inspection pipeline structural monitoring meteocean data for pipeline geotechnical services (on- and offshore) pipeline stability analysis pipeline integrity pipeline structural analysis (using SAGE Profile) pipeline routing span prediction

2 erosion around pipeline pipeline modeling in-situ testing using the SMARTPIPE and many other services Some of the competences related to pipeline related services also presented during the 4 th International Pipeline Conference in Hannover ranges from geotechnical survey for on- and offshore pipelines. These pipeline geotechnical consultancy services include pipeline stability, trenching, backfilling and other pipe-soil interaction related issues (such as the in-situ testing using Fugro SMARTPIPE) to detailed analysis of pipe-soil interaction. Complementary to these services, Fugro is developing and commercializing the market leading pipeline analysis finite element software SAGE Profile and offers pipeline analysis (e.g. on-bottom roughness analysis, buckling, expansion, span prediction...). This paper will focus on the technique and advantages associated with accurate and detailed monitoring and modelling of onshore pipeline routes using the FLI-MAP LiDAR system. 2. The technique of Airborne LiDAR modelling The FLI-MAP 400 system is operated at a maximum altitude of 400 meters above ground level and is mostly used in combination with a rotary wing aircraft, where as the FLI-MAP 1000 system can be operated at an altitude of up to 1000 meters and can be used in combination both with a rotary wing aircraft as well as with a normal aircraft. The FLI-MAP system uses precise scanning laser technology that provides highly accurate terrain elevation data of the pipeline corridor. In addition, FLI-MAP collects raw data quicker than could possibly be achieved with traditional surveying methods and at a lower cost. Due to the manoeuvrability of a helicopter and its ability to fly slower, linear features such as pipelines can be followed with great ease and closer to the ground than an airplane. For new to be built pipelines the FLI-MAP 1000 system mounted in a suitable airplane offers the possibility to capture a significant wider swathe of up to 1000 meters in one single pass. Figure 1 The FLI-MAP system can be mounted both under a helicopter and airplane

3 While a ground crew can only survey 1 to 2 kilometres a day, FLI-MAP mounted under a helicopter can obtain a complete coverage of the corridor of an existing pipeline up to eighty kilometres in a single day, depending on final routing. The FLI-MAP equipment consists of a precise navigation system, an inertial navigation unit, a scanning laser, line scan RGB camera, two photo and two video cameras. The FLI-MAP laser transmits light pulses at a rate between 150,000 Hz (FLI-MAP 400) and 150, ,000 Hz (FLI-MAP 1000) in three directions; forward, down and backward. The point density will vary between 2 and 200 laser hits per square meter depending on altitude and flying speed. The technique behind laser altimetry relies on the measurement of the time a laser light pulse sent by the scanner needs to make round trip from the scanner to the surface of the earth and back. Figure 2 The LiDAR principle Knowing the time and the speed of the light it is possible to derive the distance between the aircraft and the surface point reached by the pulse. The position of the aircraft is determined using the Global Positioning System (GPS), using a technique known as differential kinematics solution. By combining the distance and position information, the coordinate of the point from which the laser pulse has reflected on the earth s surface can be calculated. This provides the FLI-MAP laser data points with their coordinate values accurate to ± 4 cm absolute (height accuracy) and ± 1.5 cm relative for hard level surfaces at survey altitudes up to 400 meters.

4 Figure 3 Example of the FLIP7software; laser point cloud, photo imagery and 3D visualization of raw data The collected information is initially processed inside specialised software (FLIP7) to handle LiDAR data. The next step involves the generation of a digital surface model and optionally the mapping and classification of all the laser points into several categories - such as ground, buildings, vegetation and roads. Not only does the FLI-MAP system measure heights and locations using laser, it is also equipped with video and photo cameras and a line scan camera. One photo camera and one video camera are facing forward in an oblique angle, while a second photo and video camera point straight down. The image resolution achieved in a typical mission is 2-10cm per pixel for the downward photos, depending on the survey altitude. Both the video and the high resolution photos are used during processing of the laser data to gain a better understanding of the terrain that is being surveyed. The imagery is delivered to the end clients in the form of an ortho rectified image mosaics and geo-referenced video s. This imagery can then be incorporated into client s information systems. With the line scan camera a RGB-value (Red Green Blue) can be assigned to the laser data. As a laser point cloud can be studied from various view angles, integration the RGB-values offer the user a realistic 3D visualization of the project area. A good interpretation of the local possibilities provides design engineers and maintenance managers with valuable information to evaluate the options and choose for the most optimal approach. The results of airborne modelling can be presented to the users in various different formats. Although many millions of laser points can be collected in a single kilometre, this data is of little use if not being processed and vectorised into client friendly formats. The data acquired

5 by FLI-MAP can be used for among others generating large scale topographic maps, contour maps, Digital Surface Models and Digital Elevation Models. In general the data is processed to either CAD files (Autocad, Microstation etc) or to GIS files such as ESRI, Geomedia and SmallWorld. Once this is done different forms of analysis can be quickly performed. 3. The need for accurate and detailed topographic information 3.1 Asset Management Pipeline managers need a multitude of data in order to satisfy operational and maintenance needs. Not only information is needed regarding actual 3D position of the pipelines, also non engineering data regarding the right of way management is needed, such as property ownership, land use and ease of access for emergency response. To obtain these data pipeline operators need to regularly inspect, collect and update accurate spatial data regarding their facilities and its topographic surrounding. When collecting topographic information on long elongated corridors such as pipelines several problems usually arise when using traditional land survey techniques. One of these problems is the ease of access. When the pipelines traverse privately owned land it is a long and painstaking process to obtain permissions to enter these properties. Also the survey of road or railway crossings can result in substantial time consuming safety measurements that can be overcome when flying over these locations. Another problem is the amount of time it takes to survey several hundred of kilometres, also when this is performed by different field crews it is inevitable that a dataset of uniform quality is difficult to obtain. 3.2 Clearance issues and updating existing documentation Many of the pipelines currently in service were built in the late sixties early seventies, with lines installed decades earlier not uncommon. Due to the relative old age of these lines, most gas and oil pipelines operators encounter the same types of maintenance issues. Asset management, maintaining reliability, extending the useful life of lines, preventing failures, and ensuring employee and public safety are key aspects. Modeling the pipeline corridor using the FLI-MAP system combined with updated coordinate information of the pipeline, using an intelligent scout or a ground penetration radar gives an accurate and above all undisputed insight as to where the pipelines are (not where they were designed to be!) and their 3D relation to all surrounding objects such as vegetation, buildings, roads, street poles, fences and other objects. Furthermore the comparison of the height coordinates of the pipeline with the digital surface model produced out of the FLI-MAP laser data immediately provides a clear overview of locations with a critical height of ground coverage.

6 Figure 4 Ortho-rectified photo imagery integrated in a GIS for control purposes 3.3 New Routing Pipeline operators continually face the challenge to satisfy the growing demand for energy and raw materials. Also the exploitation of new sources and building of new industrial facilities results in higher need for new pipelines. Difficulties in acquiring rights-of-way, the obtaining of environmental approvals and last but not least the costs involved are challenging issues for pipeline engineers. Especially in very dense populated areas there is a serious need for a detailed and accurate data set of the corridor. Within the available corridor width (in Europe generally not more then meters) engineers and planners must find the most optimal route of the pipeline. The advantage of having a very precise digital data set offers engineers the chance if necessary to adjust the final routing within the captured corridor without sending out surveyors perform with high precision predictive analysis of the construction work visualise the corridor with a high resolution ortho-rectified photo mosaic and use these imagery for documentation and external communication purposes.

7 Figure 5 Example of a future pipeline Figure 6 Digital Terrain Model based on raw data Figure 8 Determination of non ground objects including heights

8 Figure 9 Visualization in 3D for better insight of the location Figure 10 Final documentation map including all third party information 4. Experiences in Germany Since 2002 we are working with FLI-MAP laser data, says Mr. Wolfgang Weinhold. We started with the EPDC pipeline project and mapped a major part of the route based on the FLI-MAP data. The intended route of 520 kilometres was planned to go from the Rotterdam harbour, through The Netherlands, via Belgium, back to the Netherlands and then into Germany. Instead of having this multinational project surveyed by various traditional surveying companies, the mapping of the data could be done based on one homogeneous data set. As surveying and independent consultancy company we must know what is in the interest of our clients. Over the years we have experienced the added value of a very detailed and accurate digital data set. Many times, one forgets that data captured can be used for various other purposes. Not only the adjustments of the final routing, but also positioning the construction equipment, integration third party line routes and even in a much later stage laser data and imagery can be used as evidence of how the terrain looked like prior to the construction works as the digital data can not be manipulated.

9 Considering al these advantages and multiples usages we have pursued our clients to implement the airborne laser scanning methodology of Fugro. Over the years the FLI-MAP system has proven to be the most reliable and innovative system providing unmatched data quality. Such example is the integration of the line scan data, as by capturing RGB values a realistic 3D visualization of the terrain is possible. Such insight is of unthinkable value as it provides design engineers and maintenance managers with valuable information to evaluate the options and choose for the most optimal approach. We estimate that in overall the implementation of the FLI-MAP system results in minimum cost savings of 20% or more considering the increased efficiency and added information value. It is obviously that already the major pipeline operators in Germany have chosen for this methodology and it is likely that laser scanning might be obligatory for future route surveys. Mr. Wolfgang Weinhold, General Manager of VIB-Weinhold a specialised pipeline surveying and independent consultancy company in Erkelenz - Germany and one of the founders of the NaviSAT Association in Nordrhein Westfalia Germany. Since 1991 the company VIB- Weinhold is specialised in pipeline survey projects, started with traditional surveys methodologies, via GPS and focussed on laser scanning. Since 2002 he executed FLI-MAP pipeline surveys exceeding 1500 kilometres of both existing as well as new to be built pipelines for various well known pipeline operators in Germany.

10 Figure 11 3D Visualization by combining laser and RGB data 5. Conclusion Pipeline managers are faced with an increased need for detailed and accurate information. Both for existing as well as for new to be built pipelines it is important to have accurate and up to date geographic information of the pipeline corridors either for documentation or for predictive analysis of construction studies prior to engineering works. Collecting this information over long distances is time consuming and expensive. Topographic information cannot be collected in a uniform and fast way using traditional land survey techniques. The FLI-MAP system has proven to be an excellent system capturing a complete and accurate data set. One of the main benefits of using the FLI-MAP system is the fact that the detailed and accurate data can be used for a multitude of applications that have been mentioned in earlier chapters such as asset management, clearance issues and its visualisation options for documentation purposes or design studies. Once the data is acquired the processing of the data can be executed with a specific application in mind, the data is then stored and relevant information for future applications can then be extracted once needed. Şuri Bayirli Sr. Sales Manager Fugro Aerial Mapping BV Dillenburgsingel HW Leidschendam, the Netherlands Phone: s.bayirli@fugro.com