Aerial Data Acquisition for NAKSHA PROJECT

Methodologies On

What is Aerial Data Acquisition in NAKSHA ?

• Aerial Data Acquisition is a method of collecting Geographical information about the Earth's surface from above (120 mtr. Altitude )using Aircraft, Drones (Unmanned Aerial Vehicles) or Satellites.
• This process involves through LiDar systems, high precision film cameras, and digital imaging sensors without direct physical contact with the ground.

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Key Components of Aerial Data Acquisition

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PLATFORM:

Aircraft: Can cover large areas efficiently.

Drones (UAVs): Offer high-resolution images and flexibility in deployment.

Satellites: Provide broad coverage but may lack high resolution.

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SENSOR:

Photography: Captures visual data for mapping and analysis.

Laser Scanning (LiDAR): Creates precise 3D models of terrain and features

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Methodologies adopted for Aerial Data Acquisition in NAKSHA

Nadir

(Vertically Oriented) Imaging

Oblique

(Tilt Angled)

Imaging

Combined Oblique

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LiDAR System

NADIR IMAGERY

Characteristics:

• Captured with the camera pointing directly downwards (90-degree angle to the ground).
• Provides a bird's-eye view with minimal distortion in the center. Ideal for capturing detailed ground features.

Nadir imagery refers to capturing images directly downward sensors, perpendicular to the ground. The camera's optical axis is aligned vertically with respect to the earth's surface.

• Ensures minimal perspective distortion, making it ideal for ortho-image generation.
• Best suited for mapping flat terrain and capturing large areas efficiently

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OBLIQUE IMAGERY

Oblique imagery involves capturing images at an tilt angle (typically between 30° to 60° from vertical) rather than straight down. These images provide a perspective view of features, including the sides of buildings and other vertical structures.

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Characteristics:

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• Captured at an tilt angle (typically 40° to 50°) rather than straight down.
• Provides a wider view of structures and is useful for identifying features obscured in nadir images.
• Best suited for mapping flat terrain and capturing large areas efficiently.

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COMBINED OBLIQUE + LiDAR SYSTEM

This system integrates oblique cameras with LiDAR (Light Detection and Ranging) sensors to capture both visual imagery and precise elevation data. LiDAR uses laser pulses to measure distances and generate high-resolution 3D point clouds.

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Characteristics:

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• Provides both textural detail (from oblique imagery) and accurate elevation data (from LiDAR).
• Highly effective for mapping dense vegetation or rugged terrains where photographic imagery alone may not be sufficient.
• Enables the generation of Digital Surface Models (DSMs) and 3D models with enhanced accuracy.

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Raw Data of LiDAR

A Outcome Sample of LiDAR Sensor Data

A COMBINE FEATURES

Work flow for ORI/3D Model Generation

1. Fixing AOI 2. Flight Plan 3. Fly and capture 4. Process data 5. Deliver ORI

Input Data set

• 2D Imagery

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• 3D elevation Data

A sample outcome of Oblique Camera

Processed Data Set

• ORI (Orthorectified Images)
• Ortho Mosaic
• Elevation Model (DSM, DEM, DTM)
• 3D reality model

ORI refers to an orthophoto that has been geometrically corrected (Orthorectified) to ensure that the scale is uniform across the image. This means that the image can be used as a true map, where distances measured on the image correspond accurately to distances on the ground. ORIs are often used in geographic information systems (GIS) for mapping and analysis.

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Ortho Rectified Image

True Orthorectified Images (ORI)

Outcome of NADIR Camera,

a sample ORI for better understanding

True Orthorectified Images (ORI)

Outcome of NADIR Camera,

a sample ORI for better understanding

Elevation Models

1. Digital Surface Model (DSM):- It represents the Earth's surface, including all objects on it, such as buildings, trees, and other structures. It captures the elevation of the "first surface" encountered by sensors and is commonly used in urban planning, telecommunications, and visualization applications. DSMs provide a comprehensive view of surface features but do not filter out non-ground elements.

2. Digital Elevation Model (DEM):- It is a representation of the Earth's surface that includes only bare earth elevations, devoid of natural and human-made features like vegetation and buildings. DEMs are primarily used for terrain analysis, hydrological modeling, and land-use planning. They serve as a foundational layer in GIS applications.

3. Digital Terrain Model (DTM):- It is a refined version of a DEM that represents only the ground surface while incorporating additional information about terrain features such as rivers and ridges. DTMs are often manually corrected for accuracy and are used in engineering projects, land surveying, and flood modeling. They provide a more detailed representation of terrain compared to standard DEMs.

DSM

Vs

DTM

Processed LiDAR Data

3D reality model

A 3D Reality Model is a detailed digital representation of a physical environment or object that captures its three-dimensional characteristics using technologies such as photogrammetric, laser scanning, and 3D modeling software. These models integrate spatial data to provide an accurate and interactive visualization of real-world conditions, making them invaluable in fields such as urban planning, architecture, construction management, and geographic information systems (GIS). By allowing users to explore and interact with the model from various angles, 3D reality models enhance understanding and facilitate informed decision-making in complex projects.

Sample 3D Reality Model of an Area in Delhi

Sample 3D Vector Model

Thank You �All