Terrester laserskanning för inmätning av spåranläggningar

Järnvägarna är i dag hårt belastade med trafik och är känsliga för störningar. Banverksarbeten är därför något som måste noggrant planeras och genomföras så att det medför så lite störningar som möjligt på järnvägstrafiken. Även säkerheten vid allt arbete som berör spårområden är en viktig faktor att ta hänsyn till. Allt arbete inom spårområdet måste därför uppfylla särskilda krav. Detta får även konsekvenser för detaljmätningar inom spårområden då spåret måste vara avstängt. Ett alternativ är att använda en terrester laserskanner som får sin placering utanför spårområdet, vilket skulle kunna vara ett mer flexibelt sätt att mäta spårmitt.Syftet med denna studie är att visa hur mätningar med terrester laserskanning (TLS) kan utföras i spårmiljö, jämföra dem mot traditionella mätningar med totalstation, samt bestämma om Trafikverkets toleranskrav kan uppnås vid TLS-mätningar i spåranläggningar.Bansträckan som var aktuell för inmätningar var ca 100 m lång. Spårinmätning utfördes med totalstation med ett intervall på 1-2 m. Det totala antalet linjepunkter som mättes in var 85 stycken, som sedan skulle jämföras med laserskanningsmätningarna. Mätningarna av samma bansträcka som utfördes med laserskanner utgick från fem olika uppställningar med ca 10 m avstånd vinkelrätt till närmaste rälen. Resultatet av jämförelsen av linjedata från de två mätningar visar på en radiell differens i plan med ett medelvärde på 3 mm och differensen i höjd visar ett medelvärde på 5 mm. För att visa på hur man kan identifiera olika objekt i punktmoln togs ett antal bilder fram, som på ett lättöverskådligt sätt visar hur mycket information som finns i form av punkter. För att ett fordon ska kunna trafikera spåret måste järnvägsnätet uppfylla kraven för s.k. lastprofiler. I punktmolnen med några enkla kommandon skapades en lastprofil. Därefter kunde den flyttas längs spårmittslinjen och ställas in i relation till alla omkringliggande objekt.TLS har under vårt arbete visat sig ha en stor potential för bestämning av spårmitten och detaljmätning inom spårområdet. Under relativt kort tid genererades stora datamängder i form av punktmoln från vilket enskilda objekt enkelt kunde urskiljas. Mätningsarbeten i ett högtrafikerat spår är omgärdat med restriktioner, men mätning med laserskanner som utförs utanför säkerhetszonen kräver i stort sett bara närvaro av en instrumentoperatör. De stora säkerhetskraven som ställs i fokus vid arbetet inom spårområden uppfylls fullständigt genom att ingen mätningspersonal behöver vistas i säkerhetszonen vid mätning med TLS.Slutsatser som kan dras av vår studie är att noggrannheten vid mätning av spårmittslinjen med TLS är jämförbar med mätning med totalstation. Kvaliten på mätningarna uppfyller de krav som ställs för mätning med totalstation av Trafikverket. Tack vare den snabba insamlingen av stora datamängder kan TLS bidra mycket vid mätning av spårområden där koncentrationen av spårobjekten är stor. Insamlad data kan sparas och eventuella missade kontroller, mätningar och visualiseringar kan utföras genom att nödvändig data extraheras ur sparade punktmolnen utan att nya mätningar behöver genomföras. Detta kan även underlätta framtida arbeten med planering och projektering då information av ett spårområde behövs i efterhand.The railways are nowadays congested with traffic and are sensitive to disturbance. Rail infrastructure works are something that must be carefully planned and executed when it involves as little disruption as possible for rail traffic. In addition safety of all activities related to railway environment should be considered. All work within the track area must therefore meet certain requirements. This may also influence detail measurements within the track areas where the track must be closed. An alternative is to use a terrestrial laser scanner that can be placed outside the track area, which could be a more flexible way to measure the centre line of the track. The aim of this study is to show how measurements with terrestrial laser scanning (TLS) can be performed in track environment, compare them to traditional measurements with total station and determine whether the Swedish Transport Administrations tolerance requirements can be achieved with TLS measurements.The section of the railway that was surveyed was about 100 m long. Track surveying was carried out with total station with an interval of 1-2 m. In total, 85 points on the track centre line were measured, which could then be compared with laser scanning measurements. The measurements with laser scanner were made from five different set ups at the distance of about 10 m at orthogonally to the nearest rail. The results of comparison of the line data from the two measurements shows a mean radial difference in a horizontal plane of 3 mm. and difference in height shows a mean of 5 mm. To demonstrate how to identify different objects in point clouds, a range of images are presented, which in an easily comprehensible format showing how much information is available in the form of points. For a vehicle, to be able to travel on rail track, must meet the requirements for so called loading-gauges. In the point clouds, a load profile was created with a few simple commands. Then it can be moved along the track center line and set in relation to all surrounding objects. In our work, TLS has proved to have great potential for determination of the track center line and detail measurements within the track area. During the relatively short time, large amounts of data in the form of point clouds were generated from which individual items could be easily distinguished. Surveying work on a busy railway is surrounded by restrictions, but TLS measurements, which can be carried out outside the security zone, require only the presence of an instrument operator. The major safety requirements that should be adhered to in surveys of track areas are satisfied completely, since no surveying staff should work in the security zone during TLS measurements. Conclusions that can be drawn from our study are that accuracy in measuring the track center line with TLS is comparable to the measurement with the total station. The quality of the measurements meets the requirements for the measurement with total station of Swedish Transport Administrations. Thanks to the rapid collection of large amounts of data TLS can contribute much in the surveys of railway areas where the concentration of objects is large. Data can be saved and any missed checks can be performed trough extraction of necessary data from the point clouds without the need for new measurements. This may also facilitate future work with the planning and design when information about a track environment is needed

Future Swedish 3D City Models—Specifications, Test Data, and Evaluation

Three-dimensional city models are increasingly being used for analyses and simulations. To enable such applications, it is necessary to standardise semantically richer city models and, in some cases, to connect the models with external data sources. In this study, we describe the development of a new Swedish specification for 3D city models, denoted as 3CIM, which is a joint effort between the three largest cities in Sweden—Stockholm, Gothenburg, and Malmö. Technically, 3CIM is an extension of the OGC standard CityGML 2.0, implemented as an application domain extension (ADE). The ADE is semantically thin, mainly extending CityGML 2.0 to harmonise with national standards; in contrast, 3CIM is mainly based on linkages to external databases, registers, and operational systems for the semantic part. The current version, 3CIM 1.0, includes various themes, including Bridge, Building, Utility, City Furniture, Transportation, Tunnel, Vegetation, and Water. Three test areas were created with 3CIM data, one in each city. These data were evaluated in several use-cases, including visualisation as well as daylight, noise, and flooding simulations. The conclusion from these use-cases is that the 3CIM data, together with the linked external data sources, allow for the inclusion of the necessary information for the visualisation and simulations, but extract, transform, and load (ETL) processes are required to tailor the input data. The next step is to implement 3CIM within the three cities, which will entail several challenges, as discussed at the end of the paper

Future Swedish 3D City Models : Specifications, Test Data, and Evaluation

Three-dimensional city models are increasingly being used for analyses and simulations. To enable such applications, it is necessary to standardise semantically richer city models and, in some cases, to connect the models with external data sources. In this study, we describe the development of a new Swedish specification for 3D city models, denoted as 3CIM, which is a joint effort between the three largest cities in Sweden—Stockholm, Gothenburg, and Malmö. Technically, 3CIM is an extension of the OGC standard CityGML 2.0, implemented as an application domain extension (ADE). The ADE is semantically thin, mainly extending CityGML 2.0 to harmonise with national standards; in contrast, 3CIM is mainly based on linkages to external databases, registers, and operational systems for the semantic part. The current version, 3CIM 1.0, includes various themes, including Bridge, Building, Utility, City Furniture, Transportation, Tunnel, Vegetation, and Water. Three test areas were created with 3CIM data, one in each city. These data were evaluated in several use-cases, including visualisation as well as daylight, noise, and flooding simulations. The conclusion from these use-cases is that the 3CIM data, together with the linked external data sources, allow for the inclusion of the necessary information for the visualisation and simulations, but extract, transform, and load (ETL) processes are required to tailor the input data. The next step is to implement 3CIM within the three cities, which will entail several challenges, as discussed at the end of the paper