2D-based indoor mobile laser scanning for construction digital mapping application

A common issue which occurs often in construction projects is how to determine the discrepancies between as-built or existing constructions and initial design. Physical manual measurement usually brings many of problems such as long measuring time, high labor consumption, and measurement error accumulation and in some cases lower accuracy. Therefore, more advanced technologies such as laser scanning and total station, which are used in geospatial mapping and surveying have been adopted in order to provide much more reliable and accurate measurements. However, technical and financial issues still constrain the widespread applications of well-known 3-dimensional (3D) terrestrial and aerial laser scanning, such as high equipment cost, complex pre-preparation, inconvenience of use and spatial limitation. This paper aims to introduce an innovative laser scanning method for indoor construction mapping. This method integrates an IMU-GPS positioning approach with a more convenient, more time saving and lower costed 2-dimensional (2D) laser scanner to realize indoor mobile 3D mapping for construction model creation, which can be integrated with Building Information Modelling (BIM) design in order to realize the applications, such as quality control of as-built construction or indoor mapping of existing building. Although compared with traditional 3D laser scanning, its accuracy and reliability cannot reach such a high level currently, experimental results still indicate feasibility, reliability and potential capability of this indoor mobile laser scanning method. It is hoped that this method will be further improved to substitute the stationary 3D laser scanning for narrow and limited construction spatial mapping in the near future

Positioning buried utilities in difficult environments

Recently an increasing number of underground pipes have been established, particularly in city centres, for different applications such as sewage, electricity, gas, water and drainage. How to detect and make a precise 3-dimensional survey of buried pipelines has become a focused issue. This paper first of all reviews four trenchless technologies for locating buried utilities with an emphasis on describing their application and limitations. It is found that there is no single technology, which is able to locate all underground utility service infrastructures, particularly for deep buried plastic pipes. Meanwhile, these trenchless detection technologies need to be integrated with positioning technologies to create maps for buried utilities. One of the most attractive positioning technologies for providing absolute global position is Global Navigation Satellite Systems (GNSS). However a large percentage of buried utilities are in urban areas, where is not ideal for GNSS positioning technology. This paper evaluates the performance of single and multi GNSS constellations by carrying out a test in a controlled environment. The results show that using combined GNSS systems improve availability in urban canyons compared with using GPS alone. In addition, this paper describes an inertial based pipeline positioning technology called ‘Ductrunner’, which can locate and position the buried objects in spite of the material and depth without extra positioning systems. An approximately 30m long test pipeline has been established to evaluate the performance of Ductrunner. The maximum positioning errors are found to be 8cm in plan and 4cm in height. This shows that this technology is very promising for measuring deep pipes over relatively short distances

Building Information Modelling in China

BIM teaching at University of Nottingham Ningbo Chin

Building information management and modelling teaching in Geospatial Engineering, Civil Engineering and Architecture

Building information modelling is currently an emerging technology within the building industry in the UK and in China as well as throughout t he world. The departments of Civil Engineering and Architecture and Built Environment at the University of Nottingham Ningbo China have been gradually introducing Building Information Modelling content into their courses over the last few years and have pl ans to further increase this area by introducing Building Information Modelling teaching at Master’s level in its Geospatial Engineering courses. The introduction of the teaching of Building Information Modelling has been seen as a priority by the Faculty of Science and Engineering and has been introduced to 1st year students as part of existing modules that traditionally teach Computer Aided Design and also by the introduction of two new optional modules in the final year of undergraduate study. The teachi ng of Building Information Modelling focuses on three main areas, management for architecture and civil engineering, Modelling using BIM modelling software from design plans, and data collection and processing for As - Built BIM model creation from laser sca nning. Teaching takes the form of standard lectures and tutorial classes but focuses more on using hands on teaching methods and group work using both equipment for data collection and software for modelling testing. To aid this teaching the University o f Nottingham will establish a BIM teaching and research lab at their campus in Ningbo. This lab will be equipped with extensive BIM software and other modelling tools and facilities that will complement the already extensive surveying and mapping equipment and software available at the Ningbo campus. This paper will outline the teaching content used and give examples of student work on the newly developed modules as well as describing planned future developments in BIM teaching at the University of Nottingh am. It also provides an example and initial analysis of these new teaching methods and how they contribute to current industry requirements. Building Information Management and Mod

Deflection characterisation of rotary systems using a ground-based radar

In the last two decades, an increase in large rotary machines/systems has been witnessed. To ensure safe operation of these systems especially due to extreme stress caused by centrifugal forces as well as the wind or water loadings, regular structural health monitoring (SHM) of the unbalanced parameters, particularly at the blade tips is necessary. For this, the use of non-contact sensors provides the most appropriate approach; however, millimetric out-of-plane deflection monitoring using non-contact sensors at distances >1 m has not been comprehensively addressed for rotary systems, like wind turbines. This study presents a modelling environment to simulate radar returns to analyse rotary systems. Employing Sammon mapping as a dimensionality reduction procedure in conjunction with 2D visualisation, the study demonstrates the characterisation of dynamic deflection parameters using a fast, portable ground-based interferometric radar (GBR). Comparisons between the GBR results with those of a Leica AR20 GPS indicate a divergence ±12.79 mm. The study utilises SHM framework to acquire, normalise, extract, and validate GBR signals within an SHM framework for structures under test or for deflection validation of the new system. Further, it contributes to the non-contact structural fatigue damage detection during design, testing, and operating stages of rotary structures blade tips

Satellite mapping in cities and below cities: how good is it now?

Global navigation satellite systems (GNSS) have existed since the launch of the US global positioning system constellation in 1978. There is an increasing need for better maps in the digital age, particularly for buried utilities. One of the most convenient methods for creating accurate maps is the use of navigation satellites for positioning. However, built-up urban areas are not ideal for the use of this positioning technology. This paper provides an update on the situation regarding GNSS and assesses how new satellites and signals are contributing to better positioning availability by carrying out a test in a controlled environment. The results show that using combined satellite systems improves availability in urban canyons in some cases, but not in all scenarios. In addition, pipeline mapping technology has been tested and been shown to be an effective means of mapping pipes deep under the ground over short distances

Investigating multi-GNSS performance in the UK and China based on a zero-baseline measurement approach

GPS is the positioning tool of choice for a wide variety of applications where accurate (cm level or less) positions are required. However GPS is susceptible to a variety of errors that degrade both the quality of the position solution and the availability of these solutions. The contribution of additional observations from other GNSS systems may improve the quality of the positioning solution. This study investigates the contribution of the GLONASS and BeiDou systems and the potential improvement to the precision achieved compared to positioning using GPS only measurements. Furthermore, it is investigated whether the combination of the satellite systems can limit the noise level of the GPS-only solution. A series of zero-baseline measurements, of 1 Hz sampling rate, were recorded with different types of pairs of receivers over 12 consecutive days in the UK and in China simultaneously. The novel part in this study is comparing the simultaneous GNSS real measurements recorded in the UK and China. Moreover, the correlation between the geometry and positional precision was investigated. The results indicate an improvement in a multi-GNSS combined solution compared to the GPS-only solution, especially when the GPS-only solution derives from weak satellite geometry, or the GPS-only solution is not available. Furthermore, all the outliers due to poor satellite coverage with the individual solutions are limited and their precision is improved, agreeing also with the improvement in the mean of the GDOP, i.e. the mean GDOP was improved from 3.0 for the GPS only solution to 1.8 for the combined solution. However, the combined positioning did not show significant positional improvement when GPS has a good geometry and availability