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Understanding Geometric Proces...
Understanding Geometric Processing of Airbus Satellite Imagery
Satellite images are invaluable for studying geographical areas, urban development and environmental change. But to use them accurately, geometric correction is necessary to eliminate distortions caused by the satellite's perspective and the way the images are captured.
This is where geometric correction comes in, aligning the images to an accurate reference system and ensuring reliable geolocation.
Airbus provides three levels of geometric correction
Airbus provides three levels of geometric correction for its satellite imagery products: Primary, Projected, and Orthorectification. Each level serves specific user needs, offering varying degrees of precision and readiness for analysis
Primary Processing, also known as "System-Ready," is the first level of geometric correction, closest to the image acquired by the sensor: it restores perfect collection conditions.
It is ideal for users who plan to perform their own production methods such as orthorectification or create a Digital Elevation Model (DEM). The data comes with a sensor model and Rational Polynomial Coefficients (RPCs) that allow users to perform their own adjustments.
Key applications of primary images
High-quality visuals for communication
Ideal for media and marketing where an optimised the purest form of the image is required
Algorithm development
Best for developing custom algorithms, especially in machine learning and AI, where raw data flexibility is needed
Key advantages of using primary images
Primary imagery offers maximum flexibility but requires significant post-processing expertise and tools. It is best suited for expert users who require raw data for precise, custom geometric corrections.
Projected correction processing: GIS-Ready imagery
The second level of geometric correction, the projected processing level, or "View-Ready," maps the images onto the Earth using a standard reference datum at a fixed terrestrial altitude.
It provides basic geometric correction and is suitable for Geographic Information System (GIS) environments, allowing for direct mapping and visualisation without the need for extensive geometric adjustments.
Key applications of projected imagery (vs. primary)
GIS Integration
Easily integrated into GIS platforms for quick mapping and analysis. For example, city planners can map current infrastructure projects without needing further corrections
Visual interpretation
Suitable for users needing to visualise satellite data without additional georeferencing corrections
Regional mapping
Useful for large-area mapping where small geometric inaccuracies due to terrain are acceptable
Pre-orthorectification preparation
Projected images serve as a good starting point for users planning to perform later orthorectification
Key advantages of using projected imagery
Projected imagery is more convenient than primary imagery because it is pre-mapped to a standard projection. Although it may still have terrain distortions, it is ready for visualisation and mapping with minimal effort.
Orthorectification: Ready for advanced analysis
The most advanced level of geometric correction is orthorectification. Airbus applies an automated process that uses the global Space Reference Points (SRP) database to remove both horizontal and vertical distortions. The result is a map-like image with accurate terrain representation, ideal for simple and direct use of the image, immediate ingestion into a GIS and advanced geospatial analysis.
Key applications of ortho imagery (vs. projected)
Precise measurements
Allows for accurate measurements of distances, areas, and geographic coordinates, crucial for land surveying, property boundary determination, and infrastructure planning
Time-series analysis
Ensures accurate image alignment for change detection across multiple dates and sensors, a must for monitoring urban growth or environmental change
Cross-sensor compatibility
Ensures consistency between different sensors such as Pléiades Neo, Pléiades, SPOT and Vision-1, making it essential for long-term multi-sensor projects
Remote sensing and terrain analysis
used in applications where terrain accuracy is essential, such as geological feature detection, agricultural monitoring and watershed analysis
Key advantages of using orthorectified imagery
Orthorectified imagery corrects for both terrain and off-nadir distortions, offering the highest positional accuracy. It is essential for surveying, time-series analysis, and precise geospatial applications.
Illustration with SPOT, Pléiades et Pléiades Neo over the same area in Dubai perfectly aligned
One of Airbus’s key innovations is the ability to align imagery from multiple satellites, such as Pléiades Neo, Pléiades, SPOT, and Vision-1, to the same global reference system. This means they are fully compatible with each other for large multi-sensor analysis projects, such as time-series studies where images from different sensors need to be compared over long periods of time.
Ensure the geometric precision of your data
Airbus offers precise geometric processing options, delivering satellite imagery suited to a wide range of needs — from raw data for custom workflows to fully orthorectified images ready for immediate use. By understanding the differences between primary, projected, and orthorectified products, you can choose the right solution for your specific project.
Download our whitepaper to learn more about Airbus satellite imagery, more details on the processing options and how OneAtlas help automate these workflows.
