RPC Geometric Correction Using DEM Tie Points
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Solution Overview
Problem
Existing methods for geometric correction of satellite images using RPCs require multiple ground control points, which are time-consuming and costly to obtain, especially for inaccessible areas, and often result in inaccurate geometric corrections due to systematic errors and complex processing requirements.
Innovation Solution
A system for automatic geometric correction using RPCs that includes an auxiliary data extraction unit, a tie point extraction unit, a first ground coordinates extraction unit, a second ground coordinates extraction unit, an RPC correction model generation unit, and an image distortion correction unit, which automatically extracts ground control points from a digital elevation model to reduce the need for physical and human resources and improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ground control points are acquired through actual measurement using GPS equipment, then accurate ground coordinates can be obtained, but considerable time and cost are required and measurement cannot be performed in inaccessible places
Solution Approach 1:
The patent uses digital elevation models (DEM) as a copy or representation of the actual terrain, extracting ground control points from the DEM data instead of physically measuring them in the field. This allows obtaining accurate ground coordinates without time-consuming field trips, especially for inaccessible areas like North Korea mentioned in the background.
2Loss of time
If the number of ground control points is reduced, then time and cost are reduced, but errors in image point selection and ground point location errors occur
Solution Approach 1:
The patent introduces digital elevation models as an intermediary data source to extract ground control points. By using DEM-derived GCPs as a mediator between the satellite imagery and the actual ground coordinates, the system can maintain accuracy with fewer control points, avoiding the need for extensive field measurements while reducing errors in image point selection.
3Device complexity
If RPC model is used for geometric correction, then processing is simplified, but systematic errors in the RPC model reduce correction accuracy
Solution Approach 1:
The patent corrects systematic errors in the RPC model by adjusting and refining the parameters used in the RPC equations. By modifying the RPC parameters based on ground control points extracted from DEM and comparing with actual ground coordinates, the system maintains the simplicity of RPC-based processing while improving geometric correction accuracy through parameter optimization.
Data Source
AI summary
The present invention relates to a technique for correcting a geometric image error calculated as a rational polynomial coefficient (RPC) only through a corresponding point extracted from a digital elevation model (DEM) and a stereoscopic image without direct measurement of a ground control point (GCP). To this end, a system for automatic geometric correction using an RPC in accordance with the present invention comprises: an auxiliary data extraction unit; a corresponding point extraction unit; a first ground coordinate extraction unit; a second ground coordinate extraction unit; an RPC correction model generation unit; and an image distortion correction unit. The auxiliary data extraction unit extracts two or more different images captured from the same ground surface and auxiliary data of the two or more different images. The corresponding point extraction unit extracts a corresponding point from the two or more different images through image matching. The first ground coordinate extraction unit extracts first ground coordinates from the corresponding point and an RPC model of the auxiliary data. The second ground coordinate extraction unit extracts second ground coordinates by using the first ground coordinates and a correlation coefficient of a DEM. The RPC correction model generation unit generates an RPC correction model by correcting the RPC model on the basis of the second ground coordinates. The image distortion correction unit corrects distortion of an image by allocating ground coordinates to each image coordinates of the image by using the second ground coordinates and the RPC correction model.