Aerial Mapping Course Notes

Course Overview

  • Title: Aerial Mapping (Pemetaaan Udara)
  • Provider: Ts. Muhammad Najib Khir Bin Othman, Founder/Director of DTI
  • Key Components:
    • Survey & Mapping (Ukur Tanah dan Pemetaan)
    • Aerial Mapping Methods (Kaedah Aerial Mapping)
    • Photogrammetry (Fotogrametri)
    • Mapping Techniques (Teknik Pemetaan)
    • Photogrammetry Products (Hasil Fotogrametri)
    • Image Quality (Kualiti Imej)
    • Hardware & Software Suggestions (Cadangan Perkakasan & Perisian)
    • Data Acquisition (Pemerolehan Data)
    • Image Processing (Pemprosesan Imej)

Survey & Mapping

  • Definition: The technique for determining the position of points on the earth's surface and measuring distances, directions, angles, and elevations between them.
    • Uses of Aerial Survey/Aerial Mapping:
    • Monitoring construction & site development
    • Volumetric calculations for bulk earthworks, stockpiles & landfill (mining)
    • Hazard assessments
    • Disaster & environmental monitoring
    • Archaeology
    • Geophysics in surveys
    • Land survey
    • Monitoring wildlife populations
    • Vegetation and ground cover analysis
    • Transportation projects alongside ground surveys.

Methods of Aerial Mapping

Ground Control Point (GCP)
  • Descriptive: Points marked on the ground with coordinates obtained manually using GPS.
  • Number of GCPs needed: Minimum 5 for accurate images.
  • Pros: Lower cost compared to RTK or PPK.
  • Cons: Time-consuming and prone to manual errors.
Real Time Kinematic (RTK)
  • Definition: Latest technology that allows drones to record coordinate positions live to a Ground Control Station via a base station.
  • Pros: No GCP required, coordinates are live.
  • Cons: Expensive and requires constant connection.
Post-Processing Kinematic (PPK)
  • Definition: Records coordinates through a base station, processed during editing.
  • Pros: No GCP or connection needed during the flight.
  • Cons: Expensive and requires post-flight data processing.

Photogrammetry

  • Definition: Process of creating one image from multiple views.
  • Applicable in both 2D mapping (more than two images from a single area) and 3D mapping (images from different angles).
  • Software: Agisoft Metashape for processing and stitching.
  • Types:
    • Close Range Photogrammetry: Using stationary cameras on tripods.
    • Aerial Photogrammetry: Using drones, balloons, helicopters, etc.
Benefits of Photogrammetry Over LiDAR
  • More cost-effective.
  • Equipment is more accessible.
  • Versatile for various tasks compared to LiDAR, which is specialized.

Mapping Techniques

  • Nadir Style: Camera pointed directly downwards (2D maps).
  • Oblique Style: Camera tilted at an angle (3D maps).
  • Photo Overlap: Essential for quality; higher overlap results in better quality but increases processing time.

Photogrammetry Products

Orthophotos
  • Uniform scale images, functioning as base maps.
Digital Surface Model (DSM)
  • Captures all surfaces (trees, buildings, terrain).
Digital Elevation Model (DEM) / Digital Terrain Model (DTM)
  • Represents the ground surface, excluding above-ground features, aiding in hydrological planning and land use.
Contour Lines
  • Lines of equal elevation derived from DEM/DTM, indicating slope steepness.

Image Quality

Factors Affecting Quality
  1. Motion Blur: Reduce drone speed and stabilize the camera gimbal.
  2. Unfocused Image: Use auto-focus settings.
  3. Vignetting: Check lighting conditions before flight.
  4. Distortion: Adjust settings when using electronic shutters.

Hardware & Software Suggestion

Hardware
  • DJI Phantom 4 RTK: RM25,000
  • DJI Phantom 4 Pro: RM8,000
  • DJI MAVIC 3 Enterprise: RM19,399
Software
  • Mission Planning: DroneDeploy, Pix4Dcapture.
  • Editing: Agisoft Metashape, QGroundControl.

Data Acquisition

  • Requires specific software depending on drone type (e.g., CTRL+DJI for DJI drones).
  • Mission Types: Polygon mission for irregular areas; Grid for rectangular; Double Grid for 3D; Free Flight for manual control.

Image Processing

Steps:
  1. Load images into Agisoft Metashape
  2. Inspect and remove unnecessary images
  3. Align images
  4. Insert GCP values
  5. Build dense point cloud
  6. Create mesh and texture
  7. Generate DEM and orthomosaic.
Dimension, Area, Volume Calculation
  1. Measure distances and areas using included tools in the software.
  2. Save measurements for reports.

Cost Factors for Aerial Mapping Services

  • Pricing is influenced by skill level, equipment used, market prices, project complexity, and area size.

  • Example Costs:

    • 2D mapping service: RM18 to RM100/hectare.
    • Stitching service: RM3 to RM5/hectare.
    • 3D mapping: Starting at RM1,000 per building or area depending on complexity.

  • End of Course Notes -