Location/Site
Encinitas Community Park NE ball fields parking lot
(33°01’53.10″N, 117°16’45.08″W)
Date
June 4, 2026
Time
11:01 AM
Executive Summary
Mission Objective
Develop a baseline spatial dataset of a municipal parking lot using nadir-only photogrammetry. The mission was designed to evaluate the effectiveness of an automated grid flight in producing an orthomosaic, a dense point cloud, a textured mesh, and a digital surface model, while documenting the strengths and limitations of consumer-grade GNSS positioning.
This dataset serves as the control mission for future comparisons involving oblique imagery, crosshatch flight patterns, and improved georeferencing methods. A nadir-only lawnmower grid was selected to establish a repeatable baseline dataset emphasizing horizontal accuracy and complete ground coverage.
Intended Applications
Potential applications include:
- Site documentation
- Relative dimensional verification
- Pavement, asset, and vegetation inventory
- Existing conditions documentation
- Baseline comparison for future site monitoring
- Capture strategy evaluation
Not suitable for:
- Engineering design
- Construction layout
- Survey-grade GIS analysis
- Legal boundary documentation
Mission Planning
Airspace
- Class G, Uncontrolled
- No TFRs
Weather Conditions
- Temperature: 66º F
- Wind: 8.7 mph, 226º SW
- Cloud Cover: BKN, 1000’ AGL
- Lighting Conditions: Overcast
Mission Success Criteria
- Complete image alignment
- Continuous orthomosaic coverage
- Minimal visible block deformation
- Relative measurements within ±5% of field measurements
- Clearly documented dataset limitations
- Safe and complete mission without any deviations
Data Capture Strategy
Flight Parameters
| Parameter | Value |
|---|---|
| Flight Pattern | Automated Lawnmower Grid (manually created) |
| Altitude | 120 ft AGL |
| Flight Duration | 12m 27s |
| Camera Angle | Nadir (-90°) |
| Front Overlap | 80% |
| Side Overlap | 65% |
| Speed | 3.13 mph |
| Photo Interval | 5 sec |
| ISO | 100 |
| Shutter | 1/2000 sec |
| Aspect Ratio | 4:3 |
| Image Capture Count | 117 JPEG (8064 x 6048) |
| Lighting | Uniform Overcast |
Quality Validation
Relative Measurement Validation
Seven independent field measurements were compared against the reconstructed model.
Results demonstrated relative dimensional agreement generally within approximately 2–4%, with one outlier associated with a table that abutted a tall fence, resulting in incomplete capture and measurement inaccuracy.
Interpretation
| Location/object | Lat/Long Coordinates | Actual (inches) | Model (inches) | Delta (Inches) | Signed Error (%) | Model Used |
|---|---|---|---|---|---|---|
| Launch area parking stall | 33°01'53.00"N 117°16'45.06"W | 92.125 | 94.08 | 1.955 | 2.12% | Ortho |
| Slab near the building | 33°01'52.40"N 117°16'46.43"W | 123 | 126 | 3 | 2.44% | Ortho |
| North sidewalk | 33°01'55.60"N 117°16'46.51"W | 185.75 | 192.72 | 6.97 | 3.75% | Ortho |
| East sidewalk | 33°01'52.34"N 117°16'44.17"W | 89.75 | 91.92 | 2.17 | 2.42% | Ortho |
| Baseball table | 33°01'50.68"N 117°16'43.70"W | 35.75 | 33.5 | -2.25 | -6.29% | Ortho |
| Manhole cover | 33°01'51.21"N 117°16'44.70"W | 27 | 27.6 | 0.6 | 2.22% | Ortho |
| Dark sidewalk (SW) | 33°01'51.20"N 117°16'45.51"W | 47.5 | 48.25 | 0.75 | 1.58% | Ortho |
| SE-NE Lightpost pad | 33°01'55.4"N 117°16'46.0"W 33°01'51.2"N 117°16'42.7"W | 504 | 502.2 | -1.8 | -0.35% | Ortho |
| SW Curb to White water pipes | 33°01'53.0"N 117°16'44.3"W 33°01'52.2"N 117°16'46.8"W | 234 | 232.73 | -1.27 | -0.54% | Ortho |
| Error Calculation | Value |
|---|---|
| Mean Signed Error (Bias) | 0.82% |
| Mean Absolute Error (MAE) | 2.31 |
| Mean Absolute Percent Error (MAPE) | 2.41% |
| Root Mean Square Error (RMSE) | 2.92 |
This dataset is suitable for educational use and approximate measurements but lacks the positional accuracy required for engineering, surveying, or legal-grade geospatial analysis.
Processing Summary
| Metric | Result |
|---|---|
| Images Reconstructed | 117 / 117 |
| Average Reprojection Error | 1.6 px |
| Average GSD | 0.6 cm/pixel |
| Sparse Points | 131,435 (98.9%) |
| Dense Points | 16.6 million |
| GPS Source/ CRS | Consumer GNSS (No RTK/PPK) |
| GPS Error RMS | .61 |
| Outputs | Orthomosaic, DSM, DTM, Point Cloud, Mesh |
Processing completed using WebODM. Images were resized to 6048 × 4536 px to facilitate processing.
Detailed reconstruction statistics, feature counts, reprojection error, dense point counts, and accuracy metrics are documented in the attached Process Report.
Orthomosaic
Produced complete visual coverage of the project area with no significant stitching failures. Distortion is visible on roof panels and around the orthomosaic parameter.
Suitable for documentation, visual inspection, asset inventory, and approximate measurements.
Point Cloud
Successfully reconstructed terrain, pavement, vegetation, and major structures.
Observed Limitation
Building facades, vehicle sides, and tall vegetation were incompletely represented due to the nadir acquisition strategy.
Textured Mesh
Produced a coherent three-dimensional representation of the site.
Observed Limitation
Quality decreased beneath mature trees and along vertical surfaces where image geometry was insufficient. Pavement melted into the vertical surfaces of vehicles.
DSM
Successfully represented overall site topography, including the gradual elevation increase across the parking lot.
Vegetation and building heights were preserved as expected in a Digital Surface Model.
Conclusion
Lessons Learned
- How to manually create a waypoint mission that would provide adequate coverage (it took 3 tries)
- Flying the mission in a manner and time to avoid people (required 2 mission abortions and restarts)
- Established fight planning, flight logging, and processing workflow
- How to read and interpret WebODM results, models, and use measuring tools
- Objective hazards that are present when mapping a mission (people on site, birds flying in the area)
- The lack of vertical detail when only capturing nadir imagery
- Absolute and relative inaccuracies when only using consumer GNSS
- Computer memory and processing settings needed to build a high-resolution reconstruction
Final Statement
This dataset was acquired with a DJI Mini 4 Pro using nadir imagery only and processed in WebODM without RTK corrections, surveyed control points, or checkpoints. The resulting orthomosaic and 3D reconstruction provide good visual coverage of the site and demonstrate reasonable relative dimensional consistency, with field-verified measurements generally within 2–4% of observed values and an RMSE of 2.92%
However, comparison against a reference basemap indicates positional distortion and expansion, limiting confidence in absolute coordinates. Vertical surfaces, vehicle facades, and occluded areas were incompletely reconstructed due to the nadir-only capture strategy. This dataset is suitable for visualization, workflow training, and approximate measurements, but should not be used for engineering, surveying, or construction-grade decision-making.
Additional capture with a crosshatch pattern should improve the relative accuracy and positioning. Oblique capture will improve the reconstruction of vertical surfaces, such as building walls and vehicle sides, and enhance data capture under trees and overhanging structures.