Guideline for LiDAR Data Acquisition and Use

Scope

Intent

This document is meant as a guideline for using LiDAR Scanning technology for the acquisition and gathering of as-built data, and how such data may be used as an official record of condition, prior to; during; and/or at the conclusion of, construction or maintenance activities.

It is recommended that this document assist in the promotion of a corporate or an industry standardization for LiDAR data use irrespective of the discipline that the end-user is associated with.

Assumptions

It is assumed that the reader of this document has a working knowledge of the following:

  1. LiDAR and Point Cloud variants.
  2. Survey equipment and the process of establishing ground control points.
  3. 3D CAD software (for the purpose of modeling from LiDAR data).
  4. GIS software (for the purpose of generating DEM’s and ground contouring).
  5. For discussion purposes within this document the terms “LiDAR” and “point cloud” may be synonymous.

Comment:  The use of this document (in whole or in part) is the sole responsibility of the reader and is presented as reference only without any liability to the authors.

Responsibility

It is beyond the scope of this document to define the persons responsible for the management of LiDAR data as such duties should be defined within each corporate structure. However, those most qualified to ensure compliance with all aspects of LiDAR data may include the following roles:

  • Project Manager – Person with adequate knowledge of a given project scope and the required documentation process to ensure compliance with all governmental and corporate policies and procedures.
  • Engineer – Person with sufficient training and knowledge of the design and function of a specific corporate asset and the information needed for maintenance and operation.
  • Surveyor – Person with the skillset to utilize survey equipment and software to adequately measure and geo-reference a specific asset, group of assets, or the land and/or structure used to house them.
  • CAD/GIS Manager – Person with the knowledge to manage specific CAD and GIS software for the purpose of asset design, maintenance, historical reference, analysis, and compliance.
  • Consultant – Individual or corporate entity with adequate experience in one or more of the above mentioned titles.

Related Standards and Definitions

Company Standards and Best Management Practices

This section is reserved for the corporate entity to list all internal standards and policies relevant to as-built and LiDAR data gathering procedures and use. Such standards may include Design Specification; CAD; GIS; Document Management; Regulatory Compliance; Legal; or any such policies or procedures that may assist or govern personnel affecting corporate assets.

Such documents should be perused and validated on a routine basis to avoid contradictory or misleading issues.

Title                                          Description                                                              

______________________________________________________

This exercise may require the assistance of others within the organization to form a comprehensive list.

Industry Standards

This section is reserved for industry standards pertinent to the specific assets and sites whereby LiDAR scanning and other such data acquisition is being undertaken.

Title                                        Description                                                               

CFR 1040                                Performance Standard for Light Emitting Products.

______________________________________________________

______________________________________________________

This exercise may require the assistance of industry groups to form a comprehensive list. Once compiled, the list should be vetted against corporate standards and adjusted accordingly.

Definitions & Abbreviations

Title                                        Description                                                               

As-Built Data…………………… Engineering data of a given asset(s) after a construction or maintenance activity has completed.

CAD………………………………… Computer-aided Drafting/Design
Any software used to design, draft, or model an architectural, mechanical, electrical, or civil asset.

Monument……………………….. Also referred to as Benchmarks. Anchors usually affixed to rock formations, concrete, or permanent fixture and used to establish horizontal and elevation positioning for surveyors.

Control Point……………………. A fixed point of reference that has been surveyed so as to confer geophysical coordinate data to it. Such points may be utilized as targets for LiDAR scanning events as well as for registering all scans into a point cloud.

DEM……………………………….. Digital Elevation Model.

GIS………………………………….. Geospatial Information System.
Software used to geo-reference a linear or spatial entity so as to graphically display it, or provide analytical analysis on it.

LiDAR ……………………………. Light Detection and Ranging.
Mechanism used to detect a distance to a target using a pulsed laser light.

Point Cloud………………………. The accumulation of LiDAR scans into a comprehensive dataset.

Scan Registration……………… The process of combining multiple LiDAR scans into a point cloud using established control points.

Scanning Methods

LiDAR and Point Cloud data may be acquired using three differing methods.

  1. Stationary Terrestrial Scan using a tripod or other mounting device to stabilize the unit prior to scanning. This method is typical for scans targeting small areas (less than an acre), rooms, building facades, etc. and may require multiple scans to acquire the needed peripheral data. The results may provide the highest degree of accuracy and may provide the best dataset for 3D modeling within a CAD application.
  2. Mobile Terrestrial Scan using a vehicle (i.e., ATV, Truck, Train, etc.) to transport the scanner while scanning is performed. This method is typical for large sites (multiple acres) or for linear expanses (i.e., pipelines, roads, utilities, etc.) and is best suited where time and cost are preferred over point cloud density and dimensional accuracy.
  3. Aerial Scan using a drone, or manned aircraft to transport the scanner while scanning is performed. This method is reserved for,
  • areas not accessible by other methods;
  • where the physical size (e.g., miles, kilometers) warrants its use;
  • and/or where accuracy is measured in feet or meters.

Aerial LiDAR is usually paired with photogrammetry and the data is best suited for calculating ground contouring and digital elevation models (DEM) within a GIS or other related software application.

For the purpose of this document Stationary Terrestrial scanning will be the primary focus as the hardware used for this method is typically the same used for mobile scanning and the accuracy is usually superior to that gathered by aerial scans.

LiDAR Hardware Requirements

It is beyond the scope of this document to list or define all of the hardware manufacturers on the market today as the requirements necessary to perform a LiDAR scan and its related software continue to evolve. However, minimum requirements should be established to ensure a consistent dataset that is conducive to the desired use of the data at the conclusion of the scanning activity.

It is incumbent upon each organization to research the available scanning technologies, along with the consultants performing the scans, to determine a minimal hardware requirement for the scanning project.

Some consideration may include:

  • Weather conditions.

o   Can the scanner perform in extreme temperatures?

o   Can the scanner perform during precipitation events (i.e., rain, snow, fog, etc.)?

  • Lighting conditions.

o   Can the scanner perform in intense lighting conditions?

o   Can the scanner perform in no or low lighting conditions?

o   Can the scanner adjust to contrasting lighting conditions?

  • Environmental concerns.

o   Does the scanner need to be intrinsically safe for use in volatile environmental conditions?

  • Security concerns.

o   Can the scanner be restricted to a given range or scanning aperture?

  • Image quality

o   What is the maximum resolution of scan sufficient to meet the project deliverables?

o   Is color pixilation of the scan data required?

  • Point Cloud Format

o   What file formats are supported by the hardware?

  • Are these formats compatible with the in-house software needed for viewing, printing, modeling and/or analyzing the point cloud data?

After evaluating the above options a minimum hardware requirement should be established for a given project scope.

The following hardware list is provided (in alphabetical order) as a recommended minimal requirement for most industrial applications.

  • Faro, Focus X330 HDR (or better model)
  • Leica, ScanStation P40 (or better model)
  • Reigl, VZ-2000 (or better model)

Comment:  While other manufacturers and vendors exist, and may provide a product equal to or better than the ones mentioned, those mentioned herein represent scanner models that are believed to cover the widest areas of concern with sufficient point cloud quality for the most common applications where time and accessibility to the project site is limited.

LiDAR Software Requirements

The primary purpose of acquiring LiDAR data is to produce a point cloud that can be viewed (in a 3D environment), analyzed, or imported into another software offering to enhance the data use or to create a vector model from the data.

Many of the hardware vendors offer various software tools to meet the basic needs of the end-user. These applications will vary in complexity and price dependent upon the project scope and/or the end deliverables for the scanning activity. Therefore, it is incumbent upon the project personnel to fully vet these applications to ensure that the needs of all concerned individuals and teams are met.

The sections below will highlight some of the common practices of LiDAR data along with some considerations for data integration within major design and analytical applications.

Scanner Specific Apps

Most major vendors offer software applications with varying functionality for perusing the completed point cloud. However, care should be taken in ensuring that the LiDAR deliverables are not proprietary to the vendor and thus cannot be utilized with third-party applications.

Care should also be taken when specifying the file formats that the data will be delivered in (i.e., .LAS, .E57, etc.). Even though many of the more common file format types are open-source, some vendors may encode proprietary information within them that may conflict with third-party applications.

As a minimum standard the scanner software being utilized should provide the following functionality:

  1. Fully registered scans (if more than one scan is required).
  2. Ability to geo-reference the registered scan to a project specific coordinate system (if needed).
  3. Provide multiple file formats of the scan data that is compatible with in-house tools used to view, analyze, or design from the third-party applications common to the organization.
  4. Prior to the commencement of a scanning activity a representative sample should be requested from the vendor to ensure compliance with the third-party tools in use.
  5. Ability to crop, filter, deminimize, or otherwise modify the point cloud to reduce its size and/or aid in the use of the data within third-party applications.

CAD

Most 3D CAD applications can import a point cloud for use in modeling the scanned assets into an intelligent 3D model. Since point cloud files can be rather large in size, the vendor’s software solution should be utilized to reduce the limits of the scanned data and perform other functionality to enhance the modeling experience within the CAD application.

Depending on the software offerings, the end-user may have the ability to calculate centerlines of pipes; identify structural steel; or streamline the point cloud data to allow for faster import into CAD. The CAD Manager should be included in any processes that involve 3D CAD modeling of the point cloud to ensure that the LiDAR software is compatible with the CAD applications to be used.

Prior to the commencement of a scanning project the CAD Manager should determine if the final deliverable requires a referenced geographical coordinate system.

If it is required then the following should be considered:

  1. A minimum of three surveyed control points must be available for use. The size and complexity of the area to be scanned will dictate if additional control points are needed. The scanning vendor may also provide feedback on the number of controls to reach the accuracy needed for the project.
  2. If a monument or benchmark has been establish within the proximity of the scanning activity then it may be used as one of the control points.
  3. If control points need to be established then a process should be developed to identify, survey, label, and record the points for the current project. The documented control points should be archived for future activities.
  4. The CAD Team should provide a site drawing depicting the control points to be surveyed.
  5. The CAD Manager should also consult with the GIS Administrator (if a GIS Team exist within the organization) to stipulate any coordinate system requirements used to register the point cloud for data integration with GIS or other spatially enabled applications outside of the CAD environment.

Comment:  If the CAD model is not shared outside of the CAD environment and no geo-spatial data is integrated within the model, then the default cartesian coordinate system common to all CAD applications is sufficient for modeling the point cloud.

Typically, the LiDAR hardware should be set to capture data at its highest resolution to ensure that the CAD applications have the best data to model from. Such CAD models may include:

  • Plant infrastructure (e.g., Process Piping & Equipment).
  • Civil infrastructure (e.g., Bridges and roads).
  • Electrical Infrastructure (e.g., Substations).
  • Architectural & BIM (e.g., Building facade and structural integrity).

The point cloud files should be archived in similar manner as the CAD files to ensure that a complete historical record is maintained of the site condition prior to inclusion with the CAD models.

GIS

While LiDAR scans can be targeted to specific assets with a high degree of accuracy (as defined for most CAD modeling applications) large areas or linear expanses of property or infrastructure can also be managed through the acquisition of point clouds. Such areas are typically modeled with a GIS application with the emphasis being placed on geographic features managed within a standard coordinate system (i.e., Lat/Long, State Plane, etc.).

For large areas (measured is square acres or linear miles) aerial or mobile LiDAR scanning is usually the most cost effective approach. These methods of scanning can be combined with terrestrial scanning for a more comprehensive point cloud especially if there exist specific areas of the site that require a higher degree of accuracy and point density.

Most GIS applications can permit a varying degree of file formats to be imported however, the GIS Administrator should specify the point cloud file format that is best suited for the GIS applications deployed within the organization. The GIS Administrator should also establish the coordinate system used to register the point cloud prior to delivery. If the same point cloud will be used by both the CAD and GIS systems then the Project Manager should work with both system administrators to ensure compliance with both applications. If differing coordinate systems are needed then the GIS applications will be the most adaptable as it is designed to re-project the coordinate system internally, and as needed.

Since the GIS must have a coordinate system defined it is imperative that survey control points are designated. Prior to the commencement of a scanning project the GIS Administrator should verify the following:

  1. A minimum of three surveyed control points must be available for use. The size and complexity of the area to be scanned will dictate if additional control points are needed. The scanning vendor may also provide feedback on the number of controls to reach the accuracy needed for the project.
  2. If a monument or benchmark has been establish within the proximity of the scanning activity then it may be used as one of the control points providing the scanner can capture it.
  3. If control points need to be established then a process should be developed to identify, survey, label, and record the control points for the current project.
  4. The GIS Team should provide a basemap depicting the control points to be surveyed.
  5. The documented control points should be archived for future activities.

The most common usage of LiDAR data within a GIS may include:

  • DEM’s for elevation modeling and analysis.
  • Contour mapping.
  • Vegetation control.
  • Security monitoring..
  • Right-of-Way assessment and monitoring.

Viewers

Most end-users of LiDAR data utilize complex systems such as GIS and CAD which are not designed for use without substantial training and expense. Thus the need to allow anyone the ability to view and peruse the LiDAR data is paramount to the adaption of this technology. For this reason most (if not all) hardware vendors provide viewing software so that basic functionality can be applied to the point cloud. There are also numerous third-party applications that can display industry standard LiDAR data files.

The basic functionality of a free or low cost LiDAR/Point Cloud viewer is as follows:

  • Load a single scan or multiple registered scans.
  • Navigation tools to pan, zoom, and rotate the 3D image.
  • Dimensioning tools to measure distances and elevations.
  • Ability to crop, remove, or slice the image for improved clarity and more efficient use.

In addition to these, some viewers may provide additional services (at an additional expense) as follow:

  • Ability to change the coordinate system.
  • Output to a file (e.g. 3D PDF) or to another application (e.g. Navisworks)
  • Enhanced analysis tools.

The efficiency of LiDAR data is that it is available for use immediately upon the completion of the scanning event. However, it is recommended that the data be post-processed to register the individual scans and to provide any necessary QA/QC checks that may have been set forth in the project scope. Once this process has occurred the viewing application is the best means of getting the data into the hands of all interested parties. Depending upon the corporate I.T. structure the viewer may be web-based (available for use via an internet or intranet architecture), or client-based (meaning that the application is installed on a local computer). Given that the LiDAR data files can be large in size the best approach may be a web-based architecture. It is also beneficial to have a Document Management System deployed whereby the files can be archived and made available for download by the end-user.

Care should be taken to ensure that the LiDAR data is not proprietary to a specific viewing application as this may present problems with the use of the files if other applications need to access the data.

Comment: It is recommended that a standard LiDAR file type (i.e., .LAS, .E57, etc.) be established within the corporate structure that is compatible with all applications and systems deployed within the organization that will interact with the data.

Analysis and As-Built applications

A typical LiDAR or point cloud data file may be thought of as a simple database consisting of millions of points with each point having spatial data based on its coordinate system and a RGB color code (if color imaging is performed during the scan). This is why applications such as GIS, CAD, and applicable viewers can import the data and present it in a virtual 3D environment.

This is also why some applications can extrapolate the center of a pipe from points along a curve or assess that a certain algorithm is representative of structural steel. The primary analytical tool used by viewers and other applications is to visually represent elevation or height through color variances. However, elevation only represents one of three dimensions recorded by a single point. Thus, with the correct toolset the end-user can extract elevation, northing and easting, or x,y,z cartesian data from any point within the point cloud.

As-Built Record

Many organizations struggle to maintain updated or as-built construction and maintenance drawings due to the time and expense of doing so. This usually means that prior to the commencement of the design phase of a project the current site or equipment status must be obtained and the drawings updated or created.

If properly planned and executed, LiDAR scanning may be a more efficient method of acquiring the current status of a site or asset, specifically if the drawings to be updated will be further revised or eliminated due to the project scope.

At the conclusion of a project, LiDAR scanning may be the most efficient method of collecting as-built information thus eliminating the personnel and time needed to manually ascertain the correct data. Invariably, some as-built information may be overlooked or misappropriated due to human error. This may be further complicated if the affected assets are to be backfilled (as in pipeline or utility construction) or if the operation of the site or asset restricts human interaction due to unsafe or environmental conditions.

If LiDAR scans are used to replace all or part of a drawing record then a Document Management System (DMS) should be deployed to house the data per any internal or external retention policies or regulations. The CAD Manager should be charged with the oversight of this data to ensure that the files are managed in like manner as other CAD drawings and documents.

 

LiDAR Data Acquisition

Regardless of the area being scanned, or the final deliverables of the point cloud, a comprehensive plan should be developed to ensure compliance with all entities using the point cloud data.

The following represents a plan outline for the acquisition of LiDAR data.

  1. Project Scope.
    A detailed description of the project scope and the purpose of deploying LiDAR scanning.
  2. Scanning Method.
    Identify all methods being deployed

    1. Aerial
    2. Mobile
    3. Terrestrial
  3. Hardware Specifications.
    A hardware specification sheet should be provided from the scanning vendor for all scanners being deployed to the project site.

    1. Specify minimum scan quality standards
    2. Is Color/photo capture required?
  4. Software Specifications.
    List all software applications that the point cloud will need to be compatible with.
  5. Coordinate System.
    For all software applications identified in Item #4 list the coordinate system (if needed) that the point cloud will need to be registered to.
  6. Control Points Are Control Points required for the scan?
    1. If Yes…
      1. Do Control Points already exist?
        1. If No… Develop a site map and identify the control points to be surveyed and named. Control points shall be identified using the established coordinate system for the project.
        2. If Yes… Develop a site map and identify the control points to be used along with their coordinates.
  7. Site Safety & Health Plan.
    Develop a Site Safety & Health Plan that provides:

    1. Weather conditions.
    2. Corporate Safety policy.
    3. Personal Protective Equip. (PPE) requirements.
    4. Notification procedures.
    5. Communication Plan.
  8. Site Map/Drawing
    1. For aerial LiDAR scanning
      1. Map depicting flight limits and pattern.
      2. Airspace limitations (if any).
      3. FAA clearance.
    2. For mobile LiDAR scanning
      1. Map depicting scan limits, roads, and drive path.
      2. Ingress/egress of the property.
      3. Terrain restrictions and exclusion zones.
    3. For fixed terrestrial LiDAR scanning
      1. Map depicting area and assets to be scanned.
      2. Identify below surface, or elevated areas to be scanned.
      3. Site restrictions and exclusion zones.
  9. Final Deliverables
    1. Individual scans with file names matching the names of the scanner locations.
    2. Fully registered scans based upon the established control points; coordinate system; and file type(s).
    3. Registered scan file compatible with the standard viewer.
    4. Map/drawing depicting the actual scan locations; names; and order of scan.
    5. Total Station coordinate location (northing, easting, & elevation)
    6. All still photos captured by the scanner (if used).
      1. Individual photo images must be named in accordance with the scanner location at the time of capture.
      2. Images must be deliverable in a standard format suitable for common viewer applications (i.e., .JPG, .TIF, .WMF, etc.).
    7. All still photos and/or videos captured and recorded of the project site regardless if they are pertinent to the project scope.
  10. Reports
    1. Daily Work Permits documenting time worked, work delays, names and contact information of personnel on site.
    2. Laser Scan calibration report.
    3. Total Station calibration report.
  11. Quality Report documenting scan issues and lessons learned from the event.
  12. QA/QC Plan.
    The following outlines the process of ensuring a quality deliverable upon completion of the scanning activity.

    1. Pre Scanning activity
      1. Ensure that all hardware is properly calibrated and in good working condition.
      2. Verify that the environmental conditions of the site are compatible with the scanning equipment.
      3. Know the site. Review all available maps and drawings of the site and pre-plan the scan sites.
      4. Read and understand all pertinent company policies, standards, and the project scope prior to scanning.
    2. On-site Scanning
      1. Review each individual scan prior to moving to the next scanning site.
      2. Ensure that an ample amount of redundant or overlap scanning is taking place with each scan.
      3. Have ample resources on site to remain safe if the site is active or presents potentially hazardous conditions.
      4. Ensure that open lines of communication exist with all parties.
      5. If certain aspects of the scanned area will be inaccessible upon leaving the site then review the scans for quality and coverage prior to departure.
    3. Post-Scanning activity
      1. Review the registered scan for completeness and visual quality.
      2. If an individual scan is not included within the registered site scan then depict its name and the reason for omission in the Quality Report.
      3. Ensure all deliverables are properly packaged and documented prior to submittal.
    4. Documentation control
      1. Review and document all deliverables prior to submittal.
      2. Do not delete or archive any file until all parties have accepted the deliverables.
      3. The Project Manager should ensure that all documentation and final deliverables have been properly archived based upon established corporate policies and procedures.

Conclusion

The use of LiDAR data acquisition is as varied as the companies and industries that utilize it. It is the intent of this document for provide a fundamental guideline that transcends individual use and provides foundational elements to aid in the development of this technology. It is the belief and desire of the authors that this technology will continue to grow and expand and become commonplace in the design and engineering sector of every corporation. Through articles such as this, it is our hope that the LiDAR industry can transcend the competitiveness that may exist between individual vendors to develop standards that benefit everyone.

Contribution and Influence

If additional subject matter experts wish add to, append, or revise, any portion of this document it is the author’s desire that such edits be forwarded to the contact information provided below so that a formal review can be made of the edits and a revised issue be publish for due consideration of others. In doing so, the knowledge base of all concerned will continue to evolve along with the LiDAR/Scanning industry.

Please direct any correspondence to:

Lamar Crowe       (Document author)
info@ncllc.info    (e-mail)
www.ncllc.info     (URL)

 

Revision History

Issue No. Date Description
Draft 06/01/2017 Draft release
1 07/01/2017 Initial release