Object Detection Over Water Using NDVI Spectral Analysis

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Solution Overview

Problem

Current object detection systems over water face challenges such as high false detection rates due to atmospheric conditions and time-consuming processing, which can hinder search and rescue or surveillance missions.

Innovation Solution

The system uses normalized difference vegetation index (NDVI) by acquiring image data from a storage system, determining a metric for each pixel based on radiance in the NIR and red bands, and detecting objects when the metric satisfies a criteria, thereby reducing processing time and false alarms.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If traditional object detection methods are used over water, then detection accuracy can be maintained, but processing time becomes excessive and false detection rate increases

Engineering Contradiction:
Improveprocessing speedVSAvoidfalse detection rate
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The patent transforms the detection approach by changing the parameter space from standard grayscale or color image analysis to spectral radiance analysis across multiple bands (visible, near-infrared, thermal infrared). By computing NDVI and other spectral indices, the system identifies objects based on their unique spectral signatures, which remain stable under varying atmospheric conditions. This parameter transformation enables rapid processing while maintaining high detection reliability and reducing false positives.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent introduces spectral indices (NDVI, NDWI, NDBI) as intermediary metrics that mediate between raw multi-band radiance data and final object detection decisions. These indices serve as robust intermediaries that are less sensitive to atmospheric variations compared to direct pixel intensity comparisons, thereby reducing false detections while enabling faster processing through simplified threshold-based classification.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Measurement precision

If user intervention or extensive model training is applied, then detection accuracy improves, but processing time increases significantly

Engineering Contradiction:
Improvedetection accuracyVSAvoidprocessing time
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The patent implements a self-service detection system that automatically processes multi-band satellite imagery through predefined spectral index calculations and threshold-based classification algorithms. The system does not require manual user intervention or time-consuming model training phases. Instead, it autonomously computes NDVI, NDWI, and NDBI indices, compares them against calibrated thresholds, and generates detection results directly, achieving both high accuracy and rapid processing.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent replaces complex mechanical or manual detection processes (user intervention, iterative model training) with automated computational physics-based methods. By substituting human-in-the-loop processing with algorithmic spectral analysis, the system eliminates time-consuming manual steps while maintaining or improving detection accuracy through objective, reproducible spectral thresholding.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If standard image processing techniques are used, then processing is faster, but false detections increase due to atmospheric conditions

Engineering Contradiction:
Improveprocessing speedVSAvoidfalse positive rate
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The patent moves the detection problem from two-dimensional spatial image analysis to five-dimensional spectral space by utilizing radiance values across multiple wavelength bands (visible red, near-infrared, thermal infrared). This dimensional expansion provides additional discriminatory information that enables the system to distinguish true objects from atmospheric artifacts, reducing false positives while maintaining fast processing through efficient spectral index computations.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent changes the detection parameters from standard spatial intensity metrics to spectral radiance ratios and differences (NDVI, NDWI, NDBI). These transformed parameters are inherently more robust to atmospheric conditions because they normalize out common atmospheric effects. The system processes these transformed parameters rapidly using simple arithmetic operations and threshold comparisons, achieving both speed and reliability.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentUS12315250B2Object detection over water using normalized difference vegetation index system and method
Publication Date: 2025.05.27 JOHNS HOPKINS UNIVERSITY
  • US12315250B2 patent drawing
  • US12315250B2 patent drawing
  • US12315250B2 patent drawing

AI summary

A method and a system for object detection over water are provided. The method includes acquiring, from a storage system, image data associated with a target area. The image data includes radiance of a plurality of pixels in a first spectral band and in a second spectral band. The method also includes determining a metric corresponding to a pixel of the plurality of pixels as a function of the radiance in the first spectral band and the radiance in the second spectral band and detecting an object in the target area in response to a determination that the metric satisfies a criteria.