SLAM Keyframe Pruning Using Pose Quantization Grids

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Solution Overview

Problem

Conventional SLAM algorithms face challenges in managing large volumes of keyframe data, leading to increased computational load and memory usage, with techniques like the sliding window approach potentially losing valuable environmental context and introducing map inconsistencies.

Innovation Solution

Pose quantization-based keyframe pruning, which organizes keyframes into a virtual pose grid and selectively retains keyframes based on their contribution to the environmental map, reducing redundancy and optimizing memory usage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of information

If conventional SLAM algorithms store all keyframe data, then the environmental map completeness is improved, but the memory usage and computational load increase significantly

Engineering Contradiction:
Improveenvironmental map completenessVSAvoidmemory usage
Core Design Contradiction:
Loss of informationVSQuantity of substance

Solution Approach 1:

The patent applies parameter changes by quantizing pose data from continuous to discrete representations. By organizing keyframes into a virtual pose grid with quantized spatial indices and orientation components, the system transforms the data structure to enable efficient pruning while preserving essential environmental information. This parameter transformation allows the system to maintain map completeness with reduced memory requirements.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent implements discarding and recovering by selectively pruning redundant keyframes based on quantized pose data analysis. The system identifies and removes duplicate or unnecessary keyframes from memory while preserving those that contribute unique environmental information. This selective discarding reduces memory usage while the recovery of essential keyframes maintains the completeness and accuracy of the environmental map.

Inventive Principle:
Principle #34Discarding and recovering

2Measurement precision

If conventional SLAM algorithms process all keyframe data, then the mapping accuracy is improved, but the processing time and computational load increase

Engineering Contradiction:
Improvemapping accuracyVSAvoidprocessing efficiency
Core Design Contradiction:
Measurement precisionVSProductivity

Solution Approach 1:

The patent transforms pose data parameters from continuous to quantized discrete values, enabling efficient comparison and pruning of redundant keyframes. By organizing data into a virtual pose grid with quantized spatial and orientation parameters, the system can quickly identify and remove duplicate keyframes without compromising mapping accuracy, thereby significantly improving processing efficiency.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent extracts and removes redundant keyframes from the dataset by analyzing quantized pose data. The system identifies keyframes that provide duplicate or unnecessary information and extracts only the essential, non-redundant keyframes for further processing. This extraction process reduces computational load while maintaining mapping accuracy by focusing processing resources on informative keyframes only.

Inventive Principle:
Principle #2Taking out (Extraction)

3Quantity of substance

If conventional SLAM algorithms discard older keyframe data, then the memory usage is reduced, but the map consistency deteriorates

Engineering Contradiction:
Improvememory usageVSAvoidmap consistency
Core Design Contradiction:
Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent applies parameter changes by quantizing pose data into discrete spatial indices and orientation components within a virtual pose grid. This transformation enables the system to objectively evaluate keyframe uniqueness and identify redundant data across the entire dataset, not just based on age. The quantized parameters allow for consistent comparison and pruning while preserving keyframes that contribute to map consistency regardless of their temporal position.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent performs preliminary organization of keyframes into a virtual pose grid with quantized parameters before pruning. By pre-organizing the data structure and computing quantized spatial indices and orientation components in advance, the system can efficiently evaluate all keyframes for redundancy and make informed decisions about which to retain. This preliminary action ensures that important keyframes are preserved while removing only truly redundant data, maintaining map consistency with reduced memory usage.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentUS12620129B2Pose quantization-based keyframe pruning for simultaneous localization and mapping
Publication Date: 2026.05.05 SNAP INC
  • US12620129B2 patent drawing
  • US12620129B2 patent drawing
  • US12620129B2 patent drawing

AI summary

Embodiments of the present invention relate to techniques for managing keyframe data in a Simultaneous Localization and Mapping (SLAM) system of an Augmented Reality (AR) device. The method involves obtaining a plurality of keyframes, each linked to pose data comprising spatial and orientation data derived from raw data captured by sensors. The pose data for each keyframe is quantized according to predefined parameters, creating a structured pose grid of quantized cells. The technique includes analyzing the quantized pose data to identify excess keyframes that exceed a predetermined threshold within these cells. Redundant keyframes are pruned from memory, optimizing the SLAM system's efficiency by reducing computational load and memory usage. This selective pruning process ensures that the AR device retains a comprehensive and accurate environmental map while operating within the constraints of limited system resources.