Surveying & GIS with Drones

Introduction to Drones in Surveying
- Drone technology has the potential to revolutionize survey methods for GIS professionals.
- Drones can carry out topographic surveys that offer the same quality as traditional methods but in a fraction of the time.
- Benefits include significant cost reductions and lowered workload for professionals in surveying.
Orthomosaic and Digital Surface Models
- Aerial images captured by the WingtraOne drone create orthomosaics and digital surface models.

Definition
- A drone survey involves utilizing unmanned aerial vehicles (UAVs) equipped with sensors (RGB or multispectral cameras, LIDAR) to capture aerial data.
Process
- Drones photograph the ground multiple times from varying angles, tagging each image with coordinates.
- Photogrammetry software processes these images to create geo-referenced orthomosaics, elevation models, or 3D models.
Advantages
- Drones can fly at lower altitudes, resulting in high-resolution and high-accuracy data capture.
- This process is faster, less expensive, and less impacted by atmospheric conditions compared to manned aircraft or satellites.
- Photogrammetry combines multiple images containing the same ground points to generate detailed maps and models.

Efficiency
- Drones can capture topographic data up to five times faster than traditional land-based survey methods, reducing personnel needs.
- PPK (post-processed kinematic) geo-tagging minimizes the need for numerous ground control points (GCPs), further saving time.
Access to Difficult Areas
- Drones can access previously unreachable areas, including unsafe steep slopes and harsh terrains.
- Combines operations without the need to halt road traffic or operation of trains.
Data Quality
- Each drone flight offers thousands of measurements represented in various data formats, such as orthomosaics, point clouds, and contour lines.
- Each pixel or point in 3D models provides associated geo-data, allowing for precise measurements.

Land Surveying and Cartography
- Drones produce high-resolution orthomosaics and detailed 3D models, aiding in the quick generation of cadastral maps even in complex terrains.
- Features like road signs and curbs can be extracted from the images for improved mapping.
Land Management and Development
- Drones expedite topographic surveys for land planning and management projects crucial for construction infrastructure.
- These aerial images serve as foundational data for CAD/BIM software to create 3D models that assist in construction planning and monitoring.
Precise Measurements
- High-resolution orthophotos enable accurate distance and surface measurements essential for construction and inventorying stockpiles.
Slope Monitoring
- Automated GIS analysis allows for extraction of slope measurements to aid in monitoring landslides and ground stability.
Urban Planning
- Drones streamline data collection processes for urban planners, providing real-time data on social and environmental conditions, including 3D visualization of potential developments.

Types of Data Outputs
- Depending on the camera and software used, drone surveying can yield:
- Orthomosaic maps (geoTIFF, .jpg, .png, Google tiles) — stitched images with accurate 2D measurements.
- 3D point clouds (las, .laz, .ply, .xyz) — models with spatial and color data facilitating precise area and volume calculations.
- 3D textured mesh — a detailed model for visual inspections. Formats include ply, .fbx, .dxf, .obj, .pdf.
- Digital surface models (DSM) and digital terrain models (DTM) contain height data crucial for analyzing geospatial features.

Factors Influencing Accuracy
- Drone survey accuracy can be impacted by the drone type, component quality, camera resolution, altitude, vegetation density, and geolocation method used.
Absolute Accuracy Achievements
- High-end drones like the WingtraOne can achieve an absolute accuracy of 1 cm (0.4 in) and a ground sampling distance (GSD) of 0.7 cm/px (0.3 in/px) under optimal conditions.