7.2 Aerial and Terrestrial Mapping Preparation

Domain II Knowledge B asks for procedures and requirements for aerial mapping (photogrammetric, LiDAR, UAV, control, flight plan). Knowledge C asks for procedures for preparation for terrestrial mapping (total station, GPS, LiDAR, photogrammetry). Independent OpenExamPrep teaching in this section is the preparation file: control, flight or occupy plan, and an accuracy statement you can actually test. It is not a finished contour map, not a BIM deliverable, and not the California Civil Engineering Surveying (CES) exam. Chapter 8 owns topographic field methods. Chapter 18 owns preparing topographic maps from those sources.

Decide the product and the accuracy class before you fly or occupy

Start with the same three questions Chapter 6 used for control networks: purpose, named datum, and claimed accuracy.

1. Purpose. Design-grade contours, reconnaissance planimetrics, a corridor digital terrain model, or a terrestrial as-built scan each need a different error budget. A UAV reconnaissance flight that will never be used to set a property corner is not the same product as photogrammetry that will support a grading exhibit.
2. Named control. Horizontal and vertical control must name the datum, realization, and epoch from Chapter 6. Aerial targets and terrestrial scan-spheres that sit on mixed epochs are the same PRC 8815.3 mistake as mixed CORS occupations.
3. Claimed accuracy. The American Society for Photogrammetry and Remote Sensing (ASPRS) Positional Accuracy Standards for Digital Geospatial Data, Edition 2, Version 2 (2024) report root-mean-square error (RMSE) classes (horizontal RMSEH, vertical RMSEV, and a three-dimensional class). Secondary summaries of that edition describe a 30-checkpoint floor for many projects under 1,000 km². Confirm the checkpoint count and reporting sentences in the ASPRS document for the project you are planning. Do not print "±0.10 ft UAV" and call it ASPRS.

Ground control points (GCPs) are used in the aerial triangulation or LiDAR adjustment. Checkpoints are withheld from that adjustment and used to test the product. Using the same painted cross as both GCP and checkpoint is not a test. Plan GCP density and geometry for the block or corridor; plan checkpoints in both open ground (non-vegetated vertical accuracy, NVA, in ASPRS language) and vegetated cover when the product claims a vegetated vertical class.

Aerial mapping: photogrammetry, LiDAR, and UAV flight plans

A flight plan is a survey document. It states flying height, overlap, airspace, crew, and control.

Photogrammetry. Ground sample distance is a similar-triangles relationship: GSD = (flying height × pixel pitch) / focal length, in consistent units. Worked example: pixel pitch 4.0 μm (0.000004 m), focal length 35 mm (0.035 m), planned flying height 80 m above ground. GSD = (80 × 0.000004) / 0.035 = 0.00914 m ≈ 0.91 cm. That GSD is a planning number. It is not the ASPRS RMSE class. Typical manned mapping-camera practice uses on the order of 60 percent forward overlap and 30 percent sidelap; many UAV mapping flights use higher overlap. Those percentages are typical practice, not a BPELSG-published overlap statute. Put the planned overlap in the flight plan so the triangulation has stereo coverage, including at the block edges.

LiDAR. The flight plan states swath overlap, flying height, and the pulse-density or point-density target the client specified. Do not invent a U.S. Geological Survey quality-level number as a California Board requirement if the project specifications do not name one. Plan GNSS/IMU trajectory quality the same way Chapter 6 planned control: enough satellite geometry, and enough ground control to tie the swath to the project datum. Relative swath-to-swath agreement is a LiDAR prep item; it is not a substitute for independent checkpoints.

UAV and 14 CFR Part 107. Commercial small unmanned aircraft operations run under 14 CFR Part 107. Section 107.51 operating limitations: groundspeed not more than 87 knots (100 miles per hour); altitude not higher than 400 feet above ground level, unless the aircraft stays within a 400-foot radius of a structure and not more than 400 feet above that structure's immediate uppermost limit; flight visibility not less than 3 statute miles from the control station; not less than 500 feet below and 2,000 feet horizontally from clouds. The 80 m (about 262 ft) photogrammetry example sits inside the 400-foot cap. Section 107.41: no small unmanned aircraft in Class B, C, or D airspace, or within the lateral boundaries of surface Class E designated for an airport, without prior Air Traffic Control authorization. In practice that authorization is requested through LAANC or the FAA DroneZone portal; LAANC is a request system, not a traffic display. Section 107.31 requires visual line of sight. Section 107.49 is the preflight list the remote pilot in command must complete: local weather, airspace and restrictions, persons and property on the surface, other ground hazards; brief the crew on conditions, emergencies, contingencies, roles, and hazards; confirm control links, power, and that any payload is secure. A California PLS flight plan that skips 107.49 because "we always fly this corridor" is not prepared.

California land-use or airport overlay rules may add local limits. Do not invent a city ordinance number you have not opened. Note the airspace class and any NOTAM or TFR in the flight plan.

Terrestrial mapping preparation (Knowledge C)

Terrestrial prep is the occupy plan that makes the field day repeatable.

Error sources from Domain II Knowledge U belong in this file: multipath, data input, and instrument calibration. A terrestrial laser scanner with a stale calibration occupying next to a glass curtain wall is a planned miss. A total-station layout of aerial targets must recover the same monument the flight plan named.

Do not let this section become CES. You are not interpolating a highway catch point in the field. You are not producing the Chapter 18 topographic map. You are preparing the control, the mission, and the test so that whoever later extracts contours or a point cloud can say what was planned. Independent OpenExamPrep teaching does not describe these procedures as Board-approved or sponsor-equivalent. It describes the preparation a California PLS candidate should be able to defend on Domain II.