Friday, February 12, 2010

Neither snow nor rain nor heat nor gloom of night...

With the recent snow storms impacting the country, I thought of no better topic than a discussion of weather and Mobile LiDAR.  It is relatively easy to work around localized weather events when utilizing a vehicle as opposed to an airplane or helicopter.  But sometimes, it's absolutely necessary to work in such conditions.

As discussed in earlier posts, LiDAR is an active sensor which uses a laser to measure distance to an object (same premise as total stations - traditional surveying instrument).  Therefore, our system can operate day or night and in virtually every weather condition.  We have several examples of night collections (Downtown Norfolk and I-85/285 in Atlanta), rain conditions (The Narrows - State College, PA) and now snow as shown below.


The image above was captured at our Beaver, PA office during snow flurries.  The image is colored by height to show all the snow in the scan (red dusting of points).  While the image below illustrates the same collection with the snow "cleaned" from the scan.  There are several different ways to accomplish this. But, it simply boils down to the intensity of the reflected light from the snow flakes and the elevation of those points.  Rain and snow each pose various processing challenges, but when you need information, sometimes it takes a little extra effort.

5 comments:

  1. That is all fine until you have snow piled up in the parking lot and can not count spaces. Or in curb lines and can't see the inlets/structures or the sidewalk or any utility features.

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  2. You are absolutely correct. Our system can not penetrate standing snow (or water) to measure features. In this example, there was no accumulation. I could not say the same if we were to go out and collect today.

    The purpose of this post was to illustrate that collections in adverse conditions can be done. Just because something can be done, doesn't suggest that it should or would be done.

    We develop collection plans for each project and evaluate site conditions prior to scheduling. We can augment Mobile LiDAR collection with Traditional Surveying as necessary - but when you have snow drifts and heavy accumulation, are traditional field crews digging out to measure the back of curb?

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  3. this came up in a conversation just last week, but we dont get much snow around here. Great image!

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  4. On a related topic:
    While skiing I was wondering if we could use our Lynx system to collect data of the ski slopes (like for a ski game).
    Knowing how sensitive the Lynx is to water, do you get reflections from heaps of snow? We never got the time to test it and now the snow is gone in Belgium.

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  5. I'm not sure what the information would look like. Would it almost not be better to collect the slopes, absent snow, then render the snow to various depths and compaction? It's probably easier to add that element back in, then to take it out.

    Then if you had that information for a bare earth, you have a secondary application with machine control and guidance for the snow plows to manage the slopes. Having grown up in Florida and only having skied once, I'm not certain of the market.

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What is Mobile LiDAR?

Mobile LiDAR (Light Detection and Ranging) systems are comprised of vehicle-mounted lasers, cameras and GPS/INS navigation systems to capture highly-detailed and accurate three-dimensional (3D) topographic information for surveying and engineering applications. Michael Baker International became an early adopter of Mobile LiDAR technology by acquiring our first system in 2009, with further expansions in 2014 and 2015 that increased our fleet to four (4) Optech Lynx SG1 Mobile LiDAR systems. Over that period our systems have completed more than 300 projects throughout 29 different U.S. States (and multiple countries), and encompassing hundreds of thousands of miles. Our project portfolio includes applications in roadway design, 3D modeling, railroad corridors, signaled intersections, utility infrastructure, asset management, pavement condition assessment and airport infrastructure.