Mobile LiDAR and Cross-Slope Analysis

DTS/EarthEye just completed a 9-mile mobile LiDAR scan of I-95 here in Florida and provided one of our partners with cross-slope information in a period of days.   The data was collected with our buddies at Riegl USA using their VMX-250 mobile LiDAR.  This information will be used to generate pavement resurfacing plans for the Florida Department of Transportation (FDOT).

This project shows the value that this type of project can provide to the end user on both sides of the fence.

First, the paving contractor can use this data to develop their 30% plans for submittal to FDOT when bidding on a resurfacing or re-design contract.  Having accurate and relevant data related to the roadway’s characteristics gives the paving contractor an edge over the competition because they know what the field conditions are before preparing an over-engineered design specification.  This happens all of the time because the detailed field conditions are unknown while they are preparing their plans and they only have historical information to work from.

On the other side of the fence resides the FDOT.  They can benefit from this information because if they can provide this detailed information as part of a bid package, they can reap the benefits that are gained from better information.  If all contractors have the detailed as-built information (or in this case, accurate cross-slopes), they can all prepare their submittals using the same base information.  This will provide the FDOT project manager with more accurate responses based on true field conditions, resulting in more aggressive pricing and decreased project costs.

Here are some screenshots of the information.

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LiDAR Data Viewed by Intensity and Corresponding Cross-Slope Profile

Once the data has been collected and calibrated, we generate cross-slopes at a defined interval and export those out as 3D vectors.

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These vectors are then symbolized based on their cross-slope percentages and exported as a KML file for ease of use.

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Although this is a pretty simple step, the presentation of the data in Google Earth makes it easy for the end-user to visually identify problem areas and design the corrective actions according to field measurements.

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Sign Retroreflectivity Compliance – A Geospatial Approach

We just completed a sign retroreflectivity shortlist presentation for the a client and discussed the options available for gaining compliance based on FHWA regulations as described in the MUTCD.  The client was sold on the “Blanket Replacement” method by a vendor who specializes in sign replacement.

MUTCD Retroreflectivity Guidelines

I was thinking “what a great selling strategy”, but then I thought twice about it.  This vendor had the ability to write their own ticket for selling their sign materials!  A great strategy for the vendor, but not a good option for the client.

We approached the presentation using a different approach – it combined the concept of risk with the general principles of Asset Management.  First, we would inventory their existing sign network to determine what they had and where it was.  Then, we would prioritize which areas were the most likely to fail based on the average age of the signs as well as the risk associated with the actual failure (e.g. pedestrian injury or vehicle damage due to an accident).

 

Risk Assessment for Signs

 

Sample Replacement Cost Calculation

This approach takes into consideration the entire segment of a road instead of considering an individual asset.  The client believes that it is more cost effective to replace the worst signs along a segment using a single mobilization of field crews, rather than jumping around and fixing signs based solely on their condition.  Therefore, we are combining the geospatial location, condition, age, value and MUTCD to develop a risk score for each individual sign.

Project Life Cycle

This analysis is used to create the biggest bang for the buck for our client by reducing risk related to accidents caused by failing signs.  Since all agencies have to be compliant with Regulatory, Guide and Warning signs by 2015, this approach will support a phased approach while taking care of the highest risk signs and working through the lower risk signs until all non-compliant signs have been replaced or are scheduled for replacement.

Compliance Dates for Sign Retroreflectivity

 

Valuation of Sign Asset

In conclusion, the use of Risk to support the prioritization of asset maintenance serves an appropriate role in saving clients time and money.  By replacing the highest risk assets first, an agency can reduce their exposure to lawsuits related to failing infrastructure.

Executive Dashboard

URISA Caribbean Conference in Trinidad

I am here for 3 days supporting the URISA Caribbean conference and presented to a group of Utilities who were interested in Asset Management of their electrical infrastructure.  It was interesting to hear that they have the same issues that we encounter in the US related to infrastructure preservation funding – Limited budgets, underfunded programs and failing infrastructure.

We always do our best to stay “realistic” when it comes to Asset Management.  It has not been a priority in the past and will not be one in the future – until things start failing.  The funding will never be there in the amount that it is needed, so what do you do then?

Start Small…

We had a long discussion in this workshop about starting small and working your way into a larger AMS implementation.  By starting small, you can increase the probability of success of your project and “correct the path of the ship” if something was missed or overlooked.  Select one Asset Type and focus on building it into a comprehensive database of information.  By selecting one Asset Type, you can limit the amount of effort and risk it will take to build it into your AMS.

Show it Off…

Once you have some good asset data, show it off to everyone and make sure the decision-makers understand that it is available for use.  Build charts, graphs and reports about the Asset and build a plan around getting that Asset into the work cycle for maintenance and operations.  One of the most important things I recommend is to identify the “Worst” Assets and get them fixed immediately.  These typically create liability for your agency and if left unattended, could cost more than the AMS itself.

Make it Indispensable

Once the AMS is used to make decisions and answer questions related to infrastructure, it will become the “Go To” system that your agency will use moving forward.  At that time, you will be able to show the value of the system and gain leverage in terms of future funding, new assets, etc.  At this point, no one would make the call to shut this system down because of the value it adds to everyday decision-making.

Those are some recommendations that we discussed this week – looking forward to 2 more days of collaboration and learning about Trinidad’s Utility industry!

Mobile LiDAR to Support Roadway Resurfacing

We just completed a mobile LiDAR project that was designed to support a roadway resurfacing project in Orlando.  The project was centered on the use of mobile LiDAR to generate roadway profile data that Engineers could use to design a resurfacing project.  Obviously the data would need to be accurate and we were able to hit the mark and best of all – prove it!

Overview of SR417 Project

We collected the data using the new Riegl VMX-250 mobile LiDAR unit using a single pass in the north and southbound directions.  We only required one pass in each direction to collect the road data which makes it very efficient from the data collection standpoint.  In the past, we had to collect “strips” of data and then “sew” them all together during the calibration process.  In this case, we took the opposing (NB and SB) strips and calibrated them relative to one another and then they are brought down to control as a final step.

LiDAR Coverage by Flight Line

Most of our clients are interested in the overall accuracies of the data, so we have built accuracy assessment tools that make it easy to review the LiDAR against survey control.  The tool is simple to use and allows us to sort the results and dig deeper into the least accurate points to see why there might be discrepancies in the control vs the TIN surface.

417 Accuracy Control Report

For this project, we achieved an RMSE of .0525 ft – calculated by comparing the control elevations (Z) against the TIN elevations (Z TIN).  This is important because we can check the point cloud against known control that was collected throughout the project and provide detailed information about the accuracy of the data.

Once the data has been calibrated sufficiently, we can then generate all of the derivative products for this project.  We generated the following data for our roadway engineers:

  • Pavement Cross-Slope
  • Shoulder Cross-Slope
  • 3D Roadway Markings
  • Edge of Friction Course

3D Vector Data

This data set also supports detailed engineering analysis related to guardrail height above the roadway.  This is an important factor to consider because there are specific standards that define where the guardrail is placed, more specifically, its height above the roadway, to corral vehicles that end up impacting the guardrail in an accident situation.  The following graphic displays how this measurement can be made in the point cloud data.

Guardrail Height Measurements

Pavement Management Data Analysis

We’re just finishing up on a couple of pavement re-inspection projects.  Project #1 was our 3rd re-inspection of the network and Project #2 was our second inspection of their network.  Both projects are located in the Rocky Mountain region of the US and have pretty harsh freeze/thaw cycles, particularly in the past couple of winters.  Our clients were mostly interested in how their network was performing over time as compared to our predictive models set up in their pavement management software.

The results are pretty interesting for Project #1 – as you can see, their network is deteriorating a lot faster these days based on a few harsh winter seasons.  The Bright Green lines show the distribution of their pavement in 2010 as compared to the 2008 (Yellow) and 2005 (Red) inspections.

These differences are directly attributable to the past 3 winter seasons and their impact on their pavement infrastructure.  This particular client plans on using this information to acquire additional funding for their pavement management program for the next few years to “catch up” with the maintenance on their network.  The following graphic displays the current condition distribution for this client for their most recent inspection in 2010.

Most pavement prediction models utilize performance curves to predict pavement performance over time.  These models hold true in the short-term, but can fluctuate based directly on weather events or other human factors such as changing traffic conditions.  In some cases, re-inspection is necessary to adjust these estimates so an agency can fund its capital improvement program effectively.  This was the specific intent of this client and there is no doubt why they are one of the premier places to live in because of their proactive asset management approach!


Tunneling through the Trees

Just finished collecting a site for a project with some massive overhead trees.  This wreaks havoc on the GPS signal and validates the importance of having a good Inertial Measuring Unit (IMU) on board to carry the trajectory of the vehicle during the GPS outage.  This section of road is a virtual “tunnel” of trees which makes it difficult to nail the accuracy specification of 0.1-foot with GPS alone!



Elevation Data of Roadway Obscured by Trees

The next graphic shows the same area displayed by Intensity:

Intensity Image of Canopy Road

Here is a 3D Version of the Elevation point cloud:

3D Elevation Point Cloud

And here is an elevation profile of the same area:

Elevation Profile of 3D Point Cloud

Over the next couple of weeks, we will be creating 3D vectors from these point clouds that will be used to determine the geometric characteristics of the roads.  This information will then be used as parts of safety audits related to the following information:

  • Radius of Curvature
  • Horizontal Curve (Cross-Slope)
  • Vertical Curve (Grade)

This data will then be used with crash data to determine if a road needs to be re-aligned based on its geometric characteristics.  For example, a tight curve with a high speed may be contributing to crashes on a segment of road.  This information can be used to understand precisely how a road is constructed and functioning in the real world.

Risk Analysis for Asset Management

One of the pet-peeves I have with asset management software is that they are basically Access on steroids.  There’s not much to the inner workings of the software other than showing you information about an asset – its location, street name, type and maybe some historical information.  Once you get past the attributes, the applications get very complicated because they need to handle some business logic and one-to-many relationships, etc.     The list of attributes can be exhaustive, but how much of it is useful when making a decision about what to do to an asset with limited funding.

I’m working with a vendor who understands this relationship and the role it plays in prioritizing asset rehabilitation and we are getting some promising results.  Imagine trying to prioritize which roads you will be resurfacing next year based on their condition alone.  The worse condition they are in, the higher priority they will receive when you are ranking them based on condition alone.

What if you added risk analysis into the mix?

Then, you can ask these questions of your data – If this road fails, what kind of impact will it have on the travelling public?   Does the road carry large volumes of traffic, or is it in the boonies?

If you can answer these questions, you add another level of intelligence to your data.  Start incorporating traffic volumes, functional classification, detour and access constraints  into your model and you’re on your way to prioritizing with intelligence.