Obtaining LiDAR Data, Contracting Considerations

Kenny Legleiter Project Manager

Merrick & Company

Cost Considerations

How much will LiDAR Cost? $$$$

Factors that Affect Price

Contracting mechanism

Writing of the specifications/statement of work

Entity doing the QA/QC of the data

Disk space needs

Client project management

Acquisition parameters

Acquisition sensors (LiDAR, Digital cameras, hyperspectral, thermal)

Factors that Affect Price (cont.)

Square mileage of area (cheaper by the dozen)

Shape of the project area (square or rectangular in shape is best)

Ground Sample Distance (GSD) <1 meter 1 meter 2 meter 3 meter

Factors that Affect Price (cont.)

Final Product Deliverables LiDAR only processed to bare

earth LiDAR with breaklines Contour intervals Imagery / Digital

Orthophotography

Map Accuracy Specifications ASPRS – Class 1, 2 or 3 National Standard for Spatial

Data Accuracy (NSSDA) FEMA

Number of QA/QC Points

LIDAR Cost Examples

Area (square miles)

LIDAR

GSD (ft)

meet NSSDA specification for contour Interval (ft)

LIDAR/Sq. Mile

Hydro-enforced Breaklines/Sq. Mile

Total LIDAR w/Breakline

s/Sq. Mile

100 42 (18.5 cm vertical

RMSE) $500 $150 $650

1,000 42 (18.5 cm vertical

RMSE) $200 $140 $340

5,000 42 (18.5 cm vertical

RMSE) $125 $120 $245

10,000 42 (18.5 cm vertical

RMSE) $105 $100 $205

Contracts/Agreements

What factors should be

considered when

contracting for LiDAR?

The Keys to a Successful LiDAR Project

Understand your mapping requirements and the purpose for completing a LIDAR project prior to signing of the contract.

Utilize a qualification-based selection process to select your LIDAR consultant.

Hire a LiDAR firm that owns a LIDAR sensor.

Ask for quality control plan.

Dedicate the appropriate number of internal resources to the project.

Determine who will lead the effort, act as a Project Manager

Keys to a Successful LiDAR Project (continued)

Know exactly how the quality control is going to be performed by the consultant and internally.

Understand the differences in LIDAR technology. The age of the sensor, pulse rate, roll compensation, field of view are unique to each system.

Determine which accuracy specification is going to be adhered to (i.e. ASPRS, NMAS, NSSDA, etc.).

Hybrid accuracy standards should only be used as long as there is accurate LiDAR specifications and is tailored to the project.

Keys to a Successful LiDAR Project (continued)

Include a ground truth survey component in the project. Best if completed independently of LiDAR contractor.

Request a LIDAR flight plan in the Request For Qualifications that clearly demonstrates the consultants understanding of the acquisition issues. (side overlap percentages, eye safety requirements, flight line breaks due to extreme elevation change, multiple pass areas over very tall buildings, etc.)

Make sure LiDAR specifications are in the RFP or RFQ, don’t use a traditional photogrammetry specification or use a LiDAR specifications that is several years old

Three Types of Contracts

Request for Proposals (RFP) Price key factor Common for local governments

Request for Qualifications (RFQ) Qualifications key factor Price worked out after award

Indefinite Delivery/Indefinite Quantity (IDIQ) Multiple task orders/multiple years Ex. USGS, Corps of Engineers

QA/QC of Data

Exactly how accurate is my data?

Allows users to understand “how

accurate is accurate”

Sources of Error in LiDAR Data

DGPS, Differential GPS Position of the plane (lat, long,

elevation) IMU, Inertial Measurement Unit

Attitude of the plane (pitch, roll, heading)

LiDAR Sensor Accuracy of ranging and

trajectories of shots. Calibration of data

Relative accuracy of data which is typically the greatest source of error.

Ground control survey Control creates absolute accuracy.

System Installation System mounting

Flight Acquisition Proper GPS and IMU collection

procedures Data Processing Problems

GPS processing and LiDAR boresighting

Filtering Smoothing

Helpful Hints

How is the data going to be QA/QC once it is delivered – BE PREPARED!!

Each delivery should be reviewed and commented on within 30-days of delivery

Software can be used to help with QA/QC the land cover survey points – determine accuracy by land cover

Other review methods to look for artifacts, quality of data, data formatting, flight lines not aligned, etc.

Recommend hiring an experienced company to do the review (ex. Dewberry)

Land Cover Validation Methods

QA/QC using survey equipment

Individual check points

Surveyed cross sections

Area surveys

Existing survey points

Ground Truth Surveying

Require a digital photograph of the survey shot

Land Cover Ground Truth Surveying

Detailed land-cover and land-use classification survey

Used to determine accuracy in and under vegetation

FEMA guidelines for cover class surveys

Allows users to understand “how accurate is accurate”

Individual Checkpoints

FEMA has general guidelines, but each region of the country will be different

Urban Bare ground Short grass Brush Forest

20 or more survey points per category, minimum of three land cover types

Area Surveys and Cross-Sections

Verify larger area (compared to single points)

Typically high degree of accuracy

Provides an accuracy assessment for real world applications

High Cost

Existing Control, UtilityContour Databases

Existing databases with elevations attributes(i.e., geodetic, utility surveys)

Depending on vintage, may not truly represent present conditions

Be careful of basis of survey methodology

Wrong projections/datums

Survey Control Report

Works upon analyzing control point elevations compared to their vertical intersection point of the LiDAR TIN, depending on the user defined classes enabled and disabled

Only reports vertical accuracy Contour Interval Wizard to choose from:

FGDC/NSSDA/FEMA ASPRS Class 1, 2, or 3 NMAS

RMSEz or Vertical Accuracy requirement can by manually input

Control is analyzed to TIN of DSM surface Statistics report:

Average Z Error Median Z Error Minimum Z Error Maximum Z Error

Standards report for PASS or FAIL for: Average Z Error RMSEz Vertical Accuracy

Achievable Contour Interval report for: FGDC/NSSDA/FEMA ASPRS Class 1, 2, or 3 NMAS

Selectable classes to analyze from Tabular readout of all control information Export control report to Excel file Export DSM data for the 3 points forming the TIN

of analysis for each control point

Contour Results

Contours without breaklinesDEM

Contours with breaklinesDTM

Visual InspectionShould NOT See Any of These Artifacts

Above Ground Points Not Removed

LiDAR Not Properly Calibrated

Flight lines should be within the vertical accuracy specification

QA/QC of LiDAR Data

DO NOT TAKE THIS STEP LIGHTLY, PLAN EARLY ON HOW YOU WANT

TO DO THIS!!!

Questions

Kenny Legleiter Project Manager

Merrick & Company

303-353-3837

Kenny.legleiter@merrick.com

www.merrick.com