Aerial surveying has revolutionized how we map our world. What began with photographs taken from airplanes now involves advanced drones capturing high-resolution 3D data. This transformation has significantly improved how we plan infrastructure, monitor terrain, and manage land — especially in mountainous regions like Nepal.

In this post, we explore the evolution of aerial surveying, comparing historic methods with modern drone technologies, including technical details, equipment, data outputs, and how these tools are used in Nepal today.

1. The Early Era: Aerial Photography from Aircraft (1920s–1980s)

Aerial surveying began during World War I, when military forces first used aircraft to capture images of enemy terrain. This practice quickly gained popularity in civil engineering, urban planning, and topographic mapping.

Key Milestones:

• 1920s–1930s: Governments and engineers began using aircraft-mounted cameras to map cities, farmlands, and rivers.

• 1950s: Aerial photography became a common method for topographic map creation, especially in rugged or inaccessible areas.

While effective, this method had limitations: it was expensive, weather-dependent, and required skilled pilots and heavy equipment.

How It Worked

In the early 20th century, cameras were mounted on airplanes that flew grid patterns, capturing overlapping images. These were analyzed using stereoscopes to produce 3D terrain models and contour maps.

Technical Specifications

• Cameras: Zeiss RMK, Fairchild K-17 (large-format, analog cameras)

• Aircraft: Cessna 206, de Havilland DHC-2

• Film Type: Panchromatic rolls

• Flying Altitude: 1,000–5,000 meters

• Scale: 1:25,000 to 1:50,000

• Output: Paper-based topographic maps, contour lines, orthophotos

Limitations

• Weather dependency

• Expensive flights and film processing

• Limited resolution and accuracy (~1–3 meters)

• Labor-intensive photogrammetry using analog stereo plotters

2. The Satellite Era: Remote Sensing from Space (1970s–2000s)

Overview

With the launch of satellites like Landsat in the 1970s, aerial surveys became possible without taking to the skies. Satellite imagery provided broader coverage with multispectral capabilities.

Technical Insights

• Satellites: Landsat, SPOT, IRS, WorldView

• Sensor Resolution:

  • Early: 30m (Landsat)

  • Modern: 0.3m (WorldView-3)

• Data Types: Multispectral, hyperspectral, thermal

• Software Used: ENVI, ERDAS Imagine, ArcGIS

• Common Outputs: Land use maps, NDVI vegetation analysis, regional base maps

Pros and Cons

Pros:

• Wide-area coverage

• Frequent revisit cycles

• Useful for environmental monitoring

However, satellite imagery lacked the high spatial resolution needed for many construction and cadastral projects. This paved the way for the next big leap — Unmanned Aerial Vehicles (UAVs).

Cons:

• Lower spatial resolution than drones

• Affected by cloud cover

• Not ideal for detailed engineering or cadastral work

3. The Modern Revolution: UAV Drone Surveying (2010s–Present)

Over the last decade, UAV drones have completely revolutionized aerial surveying. Compact, cost-effective, and equipped with LiDAR, multispectral, or high-resolution cameras, drones provide unmatched detail and flexibility.

What Changed?

Drones (UAVs) introduced low-altitude, high-resolution aerial surveying with GPS precision. They made surveying faster, safer, and more accessible in areas with difficult terrain — like Nepal.

Why Drones Are a Game-Changer:

• Affordability: No need for aircraft charters or satellite access

• Precision: High-resolution 2D and 3D data from low altitudes

• Speed: Survey large or remote areas quickly

• Safety: Minimal risk in hazardous terrain

In Nepal, drones are now widely used in:

• Road and hydropower planning

• Post-disaster mapping (landslides, earthquakes)

• Urban development and cadastral mapping

• Forestry and conservation

Types of Drone Surveys

A. Photogrammetry Drones

• Example Models: DJI Phantom 4 RTK, WingtraOne GEN II

• Camera Resolution: 20 MP

• Accuracy: ±3–5 cm (with RTK GNSS)

• Flight Altitude: 60–120 m AGL

• Coverage: 100–400 ha per day

• Processing Software: Pix4D, Agisoft Metashape, DroneDeploy

• Outputs:

  • Orthomosaic images

  • Digital Surface Models (DSM)

  • 3D point clouds

  • Contour lines

  • Volume analysis

B. LiDAR-Enabled Drones

• Example Models: DJI Matrice 350 + Zenmuse L2, RIEGL miniVUX

• Laser Points: 240,000–1 million points/sec

• Vertical Accuracy: ±2–5 cm

• Advantages: Penetrates vegetation, better in forested or uneven terrain

• Software: LAStools, Global Mapper, TerraScan

• Outputs:

  • Bare-earth Digital Terrain Models (DTM)

  • Classified point clouds

  • 3D topography for engineering design

4. Comparing Aerial Surveying Methods

5. Aerial Surveying in Nepal: Local Applications

Nepal’s unique topography — including hills, valleys, and flood-prone plains — makes drone surveys especially useful. Government projects, infrastructure planning, and hydropower alignments now often rely on UAV data.

Due to its difficult terrain, Nepal has quickly adopted UAV surveying for:

• Infrastructure: Road alignment, hydropower planning

• Urban Development: Topographic mapping in Kathmandu, Pokhara

• Disaster Response: Landslide mapping, post-earthquake reconstruction

• Forestry: Deforestation monitoring, canopy density analysis

Case Examples:

• Upper Tamakoshi Hydropower: Used drone and LiDAR for terrain modeling and road alignment

• Post-earthquake mapping (2015): UAVs mapped damaged zones for reconstruction planning

• Urban Planning in Pokhara and Kathmandu: High-res orthomosaics and 3D models produced via drone survey

Engineers used drone and LiDAR surveys to map steep terrain for road construction, tunnel alignment, and water flow analysis — saving time and reducing field risks.

🔗 Related reading: How drones improve mapping in South Asia – World Bank

6. Conclusion

From manual photogrammetry to real-time drone mapping, aerial surveying has become faster, safer, and more accurate. In Nepal’s diverse landscapes, UAVs have become essential tools for engineering, disaster planning, and urban development.

If you’re planning a project and need reliable terrain data, now is the time to embrace modern drone surveying.

Work with Nepal’s Drone Survey Experts

At R.R.P. Survey Consults Pvt. Ltd., we combine decades of surveying experience with cutting-edge drone and LiDAR technology.

Our Services Include:

• Topographic and engineering surveys

• Drone photogrammetry and LiDAR mapping

• Cadastral and GIS-ready datasets

• 3D modeling and terrain analysis

Contact Us Today:

📍 Kathmandu, Nepal

☎️ Landline: +977-1-5107618

📱 Mobile: 9849875800

🌐 Website: www.rrp.com.np