Scanning vs. Conventional Surveying for Large Rehabilitation and Replacement Projects July 11, 2017 Wilfred Barry and Charles Wood 2017 LGA Pipeline Safety Conference – New Orleans, LA
Surveying & Mapping 2017 LGA Pipeline Safety Conference – New Orleans, LA 2
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”. 2017 LGA Pipeline Safety Conference – New Orleans, LA 3
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?? 2017 LGA Pipeline Safety Conference – New Orleans, LA 4
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 2017 LGA Pipeline Safety Conference – New Orleans, LA 5
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 2017 LGA Pipeline Safety Conference – New Orleans, LA 6
Mobile LiDAR Scanning with a Vehicle • 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 on the road. • LadyBug Camera has full 360⁰ imaging with 6 sensors 2017 LGA Pipeline Safety Conference – New Orleans, LA 7
KML Photo Index Bootlegger Road St. Tammany Parish 2017 LGA Pipeline Safety Conference – New Orleans, LA 8
LiDAR and Imagery Photo 550 LiDAR Scan 2017 LGA Pipeline Safety Conference – New Orleans, LA 9
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 of sight distances. • Can see over roof tops and trees. • Dense foliage and grasses limit penetration of lasers. 2017 LGA Pipeline Safety Conference – New Orleans, LA 10
Drone Components 2017 LGA Pipeline Safety Conference – New Orleans, LA 11
High Resolution Photography • 4K video at up to 30fps • Record at 4096×2160 (24fps) or 3840×2160 (30/25fps) • 16MP photographs • 12.8 stops of dynamic range 2017 LGA Pipeline Safety Conference – New Orleans, LA 12
Flight Control www.DroneDeploy.com Drone Deploy 2017 LGA Pipeline Safety Conference – New Orleans, LA 13
Orthomosaic Production † † Orthomosaic generation is the automated process for Orthorectifying the raw imagery and mosaicing (stitching) them into one single image. This process will generate a Georeferenced Image and optionally a Digital surface model in various different formats. 2017 LGA Pipeline Safety Conference – New Orleans, LA 14
Selecting Photographs 2017 LGA Pipeline Safety Conference – New Orleans, LA 15
Selecting Photographs 2017 LGA Pipeline Safety Conference – New Orleans, LA 16
Creating the Orthomosaic 2017 LGA Pipeline Safety Conference – New Orleans, LA 17
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. 2017 LGA Pipeline Safety Conference – New Orleans, LA 18
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’ 2017 LGA Pipeline Safety Conference – New Orleans, LA 19
Mapping and Utility Locates 2017 LGA Pipeline Safety Conference – New Orleans, LA 20
Utility Locates 2017 LGA Pipeline Safety Conference – New Orleans, LA 21
Typical large replacement projects: Management Drivers 1. Problematic gas system conditions such as unacceptable leak histories, excessive corrosion, difficulties of 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 2017 LGA Pipeline Safety Conference – New Orleans, LA
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. 2017 LGA Pipeline Safety Conference – New Orleans, LA 23
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. 2017 LGA Pipeline Safety Conference – New Orleans, LA 24
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. 2017 LGA Pipeline Safety Conference – New Orleans, LA 25
Scanning procedures used in locating utilities cont’d 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. 2017 LGA Pipeline Safety Conference – New Orleans, LA 26
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 of underground utilities, marking and placing pin flags where needed. 2017 LGA Pipeline Safety Conference – New Orleans, LA 27
Scanning and SUE tools and procedures used in locating utilities cont’d 5. Utility locate crews performs additional locating of 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. 2017 LGA Pipeline Safety Conference – New Orleans, LA 28
Field Tools for Location Mapping 2017 LGA Pipeline Safety Conference – New Orleans, LA 29
Field Tools for Location Mapping 2017 LGA Pipeline Safety Conference – New Orleans, LA 30
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