Use of Mobile LiDAR in the Louisiana 2010 6 Inch Ortho Program Presented by Hugh Bender Sanborn Map Co. May 3 rd 2011.

Use of Mobile LiDAR in theLouisiana 2010 6 Inch Ortho Program

Presented by Hugh BenderSanborn Map Co.May 3rd 2011

Mobile LiDAR Traditional Applications

GOHSEP 6 inch Imagery Project 2010

The project was awarded in late January 2010 with the contract award 2nd week of February

Negotiations expanded the project to include the entire state at 6 inch orthos.

Time was not on our side!Over 90,000 exposures52,000+ square milesLeaf Off conditions1000 Control points

4 4

Resources • Digital DMC (4)

– 12 or 8 bits per pixel radiometric resolution

– RGB and CIR– 3cm/1.1" pixel resolution

• Digital Vexcel (2)– 16 or 8 bits per pixel

radiometric resolution – RGB and CIR– 3cm/1.1" pixel resolution

Imagery Collection AssetsDigital orthophotography 0.125 ft sample

State of Louisiana 2010 Orthos Overview.Lessons LearnedSuch a project should take about 3 months to execute

Remarkably we had a tremendous streak of good weather 4:5 days (4 days of collection out of 5) verses normal of 2:5/6 days Another assist – 2 late in the winter freezes

Mobilized 12 planes in all including all Sanborn DMC and VexcelNumerous other company planes contributed 6 planes

Contracting Hint! Schedule your contract for signing in Dec. or early January at the latest.

You can tell the contractor when to startYou can’t turn the clock back!

6Images Courtesy of Optech,WH Pacific, ADS Inc

What drove the Mobile LiDAR decision?Simple Logistics!

Already in LouisianaUSACE NO Mobile

Survey DemoUsed for a levy area.When assets are in

the same area then it becomes affordable

Plus – It had not been done!

The ProcessTraditional Process (Panels or Photo ID Points)A photogramatrist:

sets up a networkThrough google earth or similar imagery programs he identifies

specific areas for a surveyor to go out and capture a point. This alone takes weeks to accomplish, then the surveying firm(s) must cover the state. Problem areas must be reworked.

Mobile ProcessGuidelines are created and the mobile crew has much more

flexibilityLimitation = Trees and other obstructions hindering the GPS20-25 usable points per shot

Mobile LiDAR By the Facts

How this was betterNo need to set up static station to survey discrete points.

“Drive by” survey, collecting several photos ID locations within a collection swath.

Planned and collected 1100 points & used 890.Obtained 10 cm vertical or 1/3 of the RMSE

Mobile LiDAR and GOHSEP 6 inch ImageryProject 2010

PreplanningTakes some experience!  Not the same strategy as with static tripod surveys.

FeaturesOnly road features typically captured which limits some options for photogrammetric control.

Mobile LiDAR Advantages

Allowed us to pick numerous points that were visible for the orthos.

Once we had a LiDAR swath, it allowed us to pick and chose the best point

Real time savings. - better selection - multiple options- and pick the best one.

Mobile LiDAR Advantages

Traditional costs are: $250*1000 points = $250,000

Cost advantagesCan collect data at over 50 MPH, therefore saving time over longer traverse distances

TIME ADVANTAGESCan begin processing data immediately after day’s collection

Mobile LiDAR Advantages

Advantage: 1) Proved extremely useful in urban areas!2) Faster collection and processing in especially in urban areas and some rural locations3) Photogrammetrist always had several choices for ideal control location.

Mobile LiDAR Disadvantages

Disadvantage:  1)Rural areas.  To much driving and GPS limitation on remote points.  2)Trees interfere with collection.3)Coastal Areas:

1) Limited experience with coastal photo identifiable point

2) Would consider mobile lidar on a boat.

4)Had to stop more than anticipated

No Good Deed Goes Unpunished!• What we would not do. • Quick orthos after the BP Oil Spill Response.

• That worked well for the 1 foot imagery. We could process those and deliver in weeks.• Did not work for the 6 inch imagery • 6 inch imagery is no longer considered a “Quick Ortho Product. The files are so large that

it is similar to processing original ortho. 1 foot to 6 inch orthos are a 4x increase in photo sizeHad to drastically increase processing capacity for the original project,

the quickorthos made the processing problem worse.

Summary

Would we use it again? Absolutely.

Wide area and statewide rural mapping. ----------Especially when both assets are in one geographic

area. •Urban areas are prime for this type of system.

• Fast – Points collected quickly and lots of choices• Lots of points to chose from• Overall less expensive

•Works the same way when you get down to it. • A little a little more flexible because you can pick from

numerous visible points.

Hugh’s SoapboxMobile LiDAR is a great technology tool! But be careful!

Sometimes you just have to try something to see if it works. Mobile LiDAR is a viable tool for ortho production in certain

circumstancesIn general mobile LiDAR is not a replacement for everything!

Ask questions – know what you are trying to accomplish Orthos and Planimetrics are still the most useful and cost effective

tool in the remote sensing toolbox More accurate! Millimeter accuracy. Is it required?