Study Notes on Drone Surveying and GIS

Surveying & GIS

Introduction to Drone Surveying

  • Definition: A drone survey is the use of a drone (unmanned aerial vehicle or UAV) equipped with downward-facing sensors (e.g., RGB camera, multispectral cameras, LIDAR) to capture aerial data.

  • Process Overview:

    • During a survey using an RGB camera, the ground is photographed multiple times from different angles, with each image tagged with coordinates.

    • Photogrammetry software processes these images to create geo-referenced products such as orthomosaics, elevation models, and 3D models of the area.

    • Outputs can include accurate distances, volumetric calculations, and maps.

  • Advantages Over Traditional Methods: Drones operate at lower altitudes enabling faster and more accurate data collection, independent of atmospheric conditions like clouds.

Benefits of Drones in Surveying

  • Reduced Time and Cost:

    • Drone surveys can be up to five times faster than traditional land-based methods and require less manpower, significantly decreasing survey costs.

    • PPK (Post-Processed Kinematic) geo-tagging negates the need for numerous Ground Control Points (GCPs), enhancing efficiency.

  • Access to Inaccessible Locations:

    • Drones can operate in difficult terrain, such as steep slopes or remote areas where conventional equipment struggles.

    • Capability to gather data without shutting down critical infrastructure (highways, railways).

  • Comprehensive Data Collection:

    • Unlike total stations that measure single points, drones generate myriad data points in various formats (ortho-mosaics, point clouds, etc.), enhancing data richness and accuracy.

Applications of Drones in Surveying

  • Land Surveying and Cartography:

    • Generation of high-resolution orthomosaics and 3D models from areas with limited data availability.

    • Extraction of features (curbs, markers, drains) after processing images through photogrammetry software.

  • Land Management & Development:

    • Accelerates topographic surveys essential for land management, planning, and construction activities.

    • Generated imagery can be used in CAD or BIM software for engineering work, enabling real-time assessments against blueprints.

  • Precision Measurements:

    • High-resolution orthophotos offer the capability of precise distance and surface measurements.

Additional Applications

  • Volume Measurement:

    • Accurate volume assessments for stockpiles in mines/quarries can be derived from drone images.

    • The aerial perspective allows for safer data collection without on-site interruptions.

  • Slope Monitoring:

    • Use of DTMs (Digital Terrain Models) and DSMs (Digital Surface Models) generated from drone images for slope analysis, aiding in landslide prediction and prevention.

  • Urban Planning:

    • Effective data collection for urban planners allows for swift analysis of existing conditions and impacts of new developments using 3D models.

Deliverables from Drone Surveying

  • **Types of Data Generated:

    • RGB Map: Utilizes high-resolution cameras like Sony’s RX1R II or a6100.

    • Orthomosaic Maps: Accurate, fused images representing 2D geo-information (X, Y) with data formatting options (GeoTIFF, .jpg, .png).

    • 3D Point Clouds: Composed of geospatial (X, Y, Z) and color information, offering a detailed representation of surveyed areas (file formats: .las, .laz, .ply, .xyz).

    • 3D Textured Mesh: Useful for visual inspections, recreated with edges and textures of the surveyed area (file formats: .ply, .fbx, .dxf, .obj, .pdf).

    • Digital Surface and Terrain Models: Providing altitude information (Z value) and surface contour details (file formats for both include GeoTiff, .xyz, .las).

Accuracy of Drone Surveys

  • Factors affecting accuracy:

    • Drone specifications (model, camera quality), flight altitude, ground vegetation, and geo-location methodology significantly influence the precision of drone survey mapping.

  • Accuracy Levels: Under optimized conditions, drones like the WingtraOne can achieve absolute accuracy of up to 1 cm (0.4 in) and a ground sample distance (GSD) down to 0.7 cm/px (0.3 in/px).

Selection of Survey Drones

  • Ideal drones are required for different survey contexts:

    • WingtraOne Drone:

    • Capable of deploying in challenging conditions (steep terrain, adverse weather).

    • Features: VTOL (Vertical Take-Off and Landing), 42 Megapixel camera enabling high-altitude photography with low GSD.

    • Can achieve absolute accuracy down to 1 cm (0.4 in) with optimal setups including PPK functionality.

Process of Surveying with WingtraOne Drone

1. Pre-flight Preparations:

  • Check local regulations to ensure compliance with drone flight permissions.

  • Assess weather conditions for suitability (avoid rain, fog, snow, strong winds).

  • Ensure drone battery and memory storage are adequate.

2. Flight Planning:

  • Utilize the flight planning app to create survey plans by establishing key points, or importing KML files.

  • Adjust settings according to flight altitude, GSD, direction, and overlaps.

3. Setup for Flight:

  • Unpack and prepare the drone, ensuring all components are operational.

  • Verify calibration of sensors and system readiness through a checklist.

4. Flight Execution:

  • Initiate flight for automated image capture, ensuring safety protocols are followed during takeoff and landing.

5. Image Geotagging:

  • Post-flight, import images to WingtraHub for geotagging assigning X, Y, Z positional data either in metadata or a CSV file.

Data Processing for Drone Surveys

  • Images captured are processed through photogrammetry software to create orthomosaics and 3D models, enabling accurate measurements of distances, surfaces, and volumes.

  • Image Saving Solutions:

    • Images are typically saved on memory cards (like SD cards). Depending on drone technology, images may be pre-geotagged or processed with software such as WingtraHub.

  • Importing to Software:

    • Load geo-tagged images into photogrammetry software (e.g., Dronedeploy, Pix4D).

    • The processing timeframe will vary based on image quantity and computer performance (desktop vs. cloud-based software).

Comparison of Lidar and Photogrammetry

  • Use Cases: The choice between Lidar and photogrammetry depends on specific project requirements.

    • Detailed capabilities and operational considerations for both methods can be explored further at Wingtra's resources.

Conclusion

  • For inquiries, demonstrations, or detailed product information, contact Wingtra AG at Giesshübelstrasse 40, 8045 Zürich, Switzerland, or through their website.