Things can get awfully complicated...

GUIDELINES:CONTROL FOR A

MOBILE LIDAR PROJECT

THE GLUE THAT MAKES IT STICK

RELEVANT TERMS:Reference Points – Known survey locations often set at the outset of a project upon which base stations are placed during collection and to which all project control is tied throughout survey, design and construction.

Registration Points – Sometimes referred to as “transformation points” or “calibration points”, the surveyed control through-out an acquisition that ties the point cloud to the ground.

Validation Points – These points are the same as registration points except they’re not used to tie the point cloud to the ground but rather to validate accuracies of the point cloud after processing is complete.

SURVEYCREWAHEAD

SLOWDOWN

LIVES AREAT RISK

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SITE CONSIDERATIONS:The characteristics of your project site go a long way toward defining what survey control is needed to complete a mobile lidar job.

Examples include:1. Number of lanes2. Divided highway3. GPS signal due to heavily wooded area or urban canyon/tall buildings and overhead structures4. General topography of the area

THINGS TO REMEMBER:1. Use orange paint for registration points - the best color for identification in the point cloud.2. If painting numbers near each point, keep the number 2’ away from the chevron to ensure legibility3. Orient the chevrons in the direction of travel4. Place each registration point on a hard, flat surface that extends 1m2 from the PK nail5. Drive a PK nail at the tip of the chevron or at the edge of a well-defined paint line. The nail location should be surveyed.6. Keep base station placements within 3-4 miles of the mobile vehicle7. Place base station in a “GPS friendly” location (i.e. away from buildings and busy sidewalks)8. Different specs call for different control.9. Desired accuracy impacts the number and placement of registration points.

EACH CONTROL POINT IS INDICATED BY THE CHEVRON SYMBOL

The diagrams illustrated below are intended to show possible control point placement based on site characteristics

CONTROL PLACEMENT: