Scanning vs. Conventional Surveying for Large Rehabilitation and - - PowerPoint PPT Presentation

2017 LGA Pipeline Safety Conference – New Orleans, LA

Scanning vs. Conventional Surveying for Large Rehabilitation and Replacement Projects

July 11, 2017 Wilfred Barry and Charles Wood

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Surveying & Mapping

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LiDAR….Light Detection And Ranging

• The position of the mobile vehicle

is known (from differential GPS and the IMU [Inertial Measurement Unit]).

• Measures distance to surfaces by

timing the outgoing laser pulse and the corresponding return.

• Distance = time x (speed of light)/2
• By keeping track of the angle at

which the laser was fired: you can calculate the X, Y, Z position of each “return”.

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Uses of Mobile LiDAR in the Utility Industry

• Utility Corridor Mapping
• Utility Assets Mapping
• Tool for aiding design for “complicated or busy” site
• 2-D or 3-D modeling
• Construction monitoring
• As-built documentation
• The dreaded forensic documentation or analysis??

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Benefits of Mobile LiDAR

Quick turnaround Improved safety by decreasing the time crews spend in construction sites Decreases the disruption to the contractor Comprehensive, no need for costly return trips Great archival tool for later modifications Accurate locational data to 1/10 of a foot, or better with use of control Data is generated in 3-D, so there is no need for conversions from 2-D. Cost effective and practical

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LiDAR Scanner Components

• Lasers mounted in the scanner.
• Scanning assembly – precisely

controlled rotating mirror – directing the “firing” of 32 lasers.

• Receiver for recording reflected

energy called “returns”.

• Vehicle location system

incorporating Differential GPS and Inertial Navigation System (INS & IMU).

Velodyne HD32 spinning at 20 Hz, capturing up to 700,000 points per second

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• Surveying while driving
• Off road surveys with more

suitable vehicles

• Surveying crews working

conventionally on busy highways is a significant danger to the crews and the vehicles

• n the road.
• LadyBug Camera has full 360⁰

imaging with 6 sensors

Mobile LiDAR Scanning with a Vehicle

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KML Photo Index

Bootlegger Road

• St. Tammany Parish

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LiDAR and Imagery

Photo 550 LiDAR Scan

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Mobile LiDAR Scanning with a Drone

• Terrain is irrelevant…good weather is

more important.

• FAA restrictions and licensing required.
• Flight altitude limited to 400 feet

(plenty for scanner).

• Range is limited to battery life and line
• f sight distances.
• Can see over roof tops and trees.
• Dense

foliage and grasses limit penetration of lasers.

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Drone Components

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High Resolution Photography

• 4K video at up to 30fps
• Record at 4096×2160

(24fps)

• r 3840×2160 (30/25fps)
• 16MP photographs
• 12.8 stops of dynamic

range

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Flight Control

www.DroneDeploy.com

Drone Deploy

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Orthomosaic Production†

† Orthomosaic generation is the automated process for Orthorectifying the raw imagery and mosaicing (stitching) them into

• ne single image. This process will generate a Georeferenced Image

and optionally a Digital surface model in various different formats.

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Selecting Photographs

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Selecting Photographs

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Creating the Orthomosaic

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Orthomosaic Uses

Assumption: The pictures are taken using a camera that writes geographic metadata into the picture and is subsequently adjusted using visible control with GPS horizontal and vertical observations:

• Measuring distance within the Orthomosaic is as

accurate as picking the correct pixels...0.1% or better.

• The file extension is a TIF and can be used as a “texture” for

colorizing LiDAR data that has no RGB values. Because the TIF has geo-encoded elevation data, it colorizes the correct LiDAR

• points. This is why it’s important that the LiDAR data and the

Orthomosaic are using the same surveying control.

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Accuracies

Paved Surfaces Grassy Surfaces No Control 0.1 to 0.2’ 0.2 to 0.4’ With Control 0.05 to 0.10’ 0.1 to 0.2’

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Mapping and Utility Locates

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Utility Locates

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Typical large replacement projects:

Management Drivers

1. Problematic gas system conditions such as unacceptable leak histories, excessive corrosion, difficulties

• f

system repair, persistent pressure problems from piecemeal additions, etc. 2. Obsolete piping materials and/or noncompliant piping systems 3. Highway and utility improvements requiring relocation 4. Growth of demand beyond current capacity

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Typical locating and mapping requirements ahead of construction

• 1. Record maps…..are they accurate??
• 2. Main and valve locations and depths
• 3. Meter and service line locations and depths
• 4. Other utility locations – particularly wastewater

service lines – for conflict avoidance.

• 5. Desired accuracies for locating conflicts
• a. Horizontal: 2 – 3’ minimum†, 1’ preferred
• b. Vertical: expectation is normal depth for the utility,

depth data dictated by need and importance

†LA One Call allows a tolerance of 18”, each side of the facility width. This can lead to a large width for the possible location.

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Conventional procedures used in locating utilities

1. Initiate LA One Call locate requests and track results. 2. Prepare base maps from clipping recent imagery, usually from Google Earth or Bing. 3. Request record maps from utilities that do not mark. 4. Utility locate crews walk and pick up details of One Call marks, laying conditions and potential conflicts. Utility locate crews perform additional locating of underground utilities, marking and placing pin flags where needed. 5. Survey crews GPS RTK (real time) marks and “connect the dots”. 6. Survey technicians draft from images and survey notes. 7. Base map is complete and ready for design.

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Scanning procedures used in locating utilities

1. Initiate LA One Call locate requests and track results. 2. Request record maps from utilities that do not mark. 3. Prepare base maps from clipping recent imagery, usually from Google Earth or Bing 4. Utility locate crews walk and pick up details of laying conditions and potential conflicts. Utility locate crews perform additional locating of underground utilities, marking and placing pin flags where needed. 5. Truck or drone scan project streets and alignments.

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6. Survey crews GPS RTK (real time) marks and “connect the dots”. 7. Survey technicians draft from images and survey notes. 8. Base map is complete and ready for design.

Scanning procedures used in locating utilities cont’d

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Scanning and SUE tools and procedures used in locating utilities

1. Initiate LA One Call locate requests and track results. 2. Request record maps from utilities that do not mark. 3. Prepare base maps from clipping recent imagery, usually from Google Earth or Bing 4. Utility locate crews walk and pick up details of laying conditions and potential conflicts. Utility locate crews performs additional locating

• f underground utilities, marking and placing pin flags where

needed.

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5. Utility locate crews performs additional locating

• f

underground utilities, marking and recording locations using a smart tablet with GPS and imagery on board providing segregated layers by utility and owner. 6. Truck or drone scan project streets and alignments for base map purposes recording all visible topo to cm accuracies. 7. Survey crews GPS RTK (real time) marks and “connect the dots” 8. Survey technicians draft from images and survey notes imported files and alignments from the smart tablet. 9. Base map is complete and ready for design.

Scanning and SUE tools and procedures used in locating utilities cont’d

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Field Tools for Location Mapping

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Field Tools for Location Mapping

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Additional advantages of preserving location and imagery (unquantifiable)

• 1. Preserves knowledge of existing conditions (may avoid

future controversies and claims).

• 2. Provides evidence of what conditions were like before

construction started (pavement cracks, landscaping, etc.).

• 3. Genesis of record maps.

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Disadvantages of preserving location and imagery data

• 1. Data intensive: files easily get into the gigabyte size

range.

• 2. Will change back up procedures and equipment.
• 3. Archival and retrieval of the data can be problematic

with file sizes, various software types, and to provide access to those that need it.

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Costs and Production Rates

• Scanning and drone vehicle $1,500 to $2,500 per day

depending on crew requirements and mobilization

• Scan processing $1,000 per day for LiDAR and PIX4D
• Processing time is about two days to each day of scanning
• Drone scans are flown for the same area twice at 90⁰ apart and

scan up 150 to 200 acres per day (50 acre limit imposed by battery life). Linear projects about 6 to 10 miles per day flown

• ut and back.
• Vehicle scans can produce about 40 miles a day, or 20 miles of

linear projects that are scanned once in each direction.

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Software Credits…

• Inertial Explorer processing of the INS trajectory by Novatel
• Point Cloud Export and colorization by LiDARUSA
• LadyBug image processing by Point Grey Research, now
• wned by FLIR Systems, Inc.
• LadyBug Export of panorama and 2-D jpegs by LiDARUSA
• Pix4D orthomosaic by Pix4D, Inc.
• Global Mapper ground classification (DEM) by Blue Marble

Geographics

• Quick Terrain Modeler point cloud colorization and

management by Applied Imagery

• TopoDOT feature extraction for TIN and cross section development

by Certainty 3-D

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Questions?

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Thank you!!