ARRB Group has been asked by the Australian state road agencies to assess the value of mobile LiDAR for asset management. Our experience is that accuracies of the available LiDAR system vary, but for the applications you mention, the required accuracies can be realised (with the exception pavement quality measures like IRI). This means that your concerns about quality/accuracy/precision of data available are a matter of choosing the right system for the job. If you would like to consider using mobile LiDAR to replace existing condition surveys, the next questions are:
The experience of US and Australian road agencies with mobile LiDAR has been discussed in a workshop with industry partners.
Key messages were:Potential benefits of MLS is that a single acquired dataset can be used for a variety of applications Typical examples of many possible applications are:
- There are different types of mobile LiDAR systems, for example varying in accuracy. Different types have different uses. - Also, mobile LiDAR is just one tool, which needs to be augmented by stationary/aerial etc - Costs vary largely and depend on:
Main issues for road agencies to start using mobile LiDAR:
We've been doing a number of road surveys using mobile laser scanners (slightly different to LiDAR I believe). The most recent one I've been involved in is scanning 60km of road before the construction of the Ichthys Project. The NT Gov were concerned that the high number of road train movements may damage the road, so we've done the scanning so we have an accurate "before" record, and can compare it later on or at the end of the project to an "after" scan. The can pick everything up in a great level of detail, and it takes 4 high definition photographs every 10m, effectively forming your own streetview - which is has come in handy for seeing if any signs etc are damaged. There's a lot of amazing stuff that can be done with the data, and can be presented in a number of ways including using free software (Leica TruView) that allows you to take measurements etc
I'd contact Leigh Finlay for more information (and a lot more examples of the work that we've done for various road authorities) - LFinlay@globalskm.com +61 (0)2 9928 2540, Leigh is our "Practice Leader" for survey work. You can then see if something like that will suit your needs or not. Hope that helps, J-P ------------------------------------------- John-Paul Foster Senior Civil Engineer Sinclair Knight Merz - Darwin, NT Parap NT au -------------------------------------------
Brian, Contours derived by LiDAR is useful but do not define breaklines well, such as the top and bottom of kerbs, walls etc. It is a great tool for area analysis, but has limitations from a brownfield design perspective. The precision is very dependant on GPS acquisition and weather (wind conditions). Stirling uses LiDAR to contours in the City's GIS (removing buildings from the dataset), but survey field tests indicate that 0.1 to 0.2m vertical accuracies are achievable. LiDAR provides @ 4.5 laser points per square meter, however the points are scattered so that without good digitising of breaklines accuracies may not be improved. LandGate in WA are spruiking EarthMine which combines GPS and Video and the ability to take sizes and height and condition from the video. As the program uses triangulation from a short base-line of the vehicle, positional accuracy degrades with distance from the vehicle. However in the immediate road reserve this should not presenta problem except for groups assets such as signs. I'm concerned that a 20mm tripping hazard on a path at distance could not be identified. But there is some merit in a yearly video for sign condtion and gross road defects in the road reserve (So either an officer in the field or the office) . Obviously image resloutiuon is the last factor that needs to be considered,. The data that needs to be held on a server is huge (Terabytes) and will beed to be manged. An estimate for a Council the Size of Stirling @100 KM2 is around $100 000 P/A, for Earth-Mine so the sums have to add up. Regards,
Thanks for the replies folks, your comments and time are much appreciated.
What I haven't heard is a resounding 'Yes, we're using mobile LIDAR data on a regular basis to support activities x, y, and z, and it's fantastic' (please correct me if that's wrong). As such, I'm guessing that it hasn't quite developed to the point of being a key part of everyday roading business, but that it is getting closer.
I've gathered here in Calgary that the costs of LIDAR data collection have dropped dramatically over the past 5 or 10 years (by a factor of 10 by one estimate), and that the technology is becoming far more prevalent (I was told that there are now 3 LIDAR vendors situated in Calgary, where 5 years ago there were none). However, because of the high costs of data storage, we would likely need to consider non-standard approaches, such as having a consultant store the data, or putting it on a few hard drives, and those solutions bring their own issues.
To give some context to Calgary - we have just under 5,300 centreline kms of roadway, of which 1,100 are expressway or arterial (overall we have about 15,100 lane kms). So it's rather a large network even for just the bigger roads, and there would be a LOT of data to collect and store if we were to capture the whole network.
Re: the accuracies that we are currently working with, I've heard that they *might* be achieved if we select the right system, but it sounds like we would be looking at the higher-end systems in order to achieve that. I guess a key judgement we would need to make is 'how close is close enough' - which would need a full test run in order to document and verify accuracies and issues against real conditions.
All in all, a shiny toy that's very neat, has some immediately useful applications and has loads of potential, but probably not quite there yet in terms of fully supporting our needs.
The City of Calgary is now collecting airborne LIDAR/imagery, but in Roads we haven't explored the data analysis potential of that yet, we just use the resulting imagery as an enhanced orthophoto behind our GIS layers (the imagery can be viewed from an oblique angle, which can be quite helpful).
If we do pursue a full investigation of mobile LIDAR, I'll post at least a summary of the results.
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