GCP Height Adjustment for Off-Nadir Ortho Rectification Accuracy

Solution Overview

Problem

Satellite images often suffer from ortho rectification errors due to uncertainties in Ground Control Points (GCPs) and DEM errors, leading to misalignment and artifacts like building lean, which affect the precision and reliability of geolocation and mapping applications.

Innovation Solution

The method involves calculating DEM errors to determine ortho shifts, adjusting satellite images based on these shifts, and performing bundle block adjustments to improve alignment and accuracy, while using GCPs as diagnostic points to measure and correct for ortho shifts and building lean artifacts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If bundle block adjustments are used to correct satellite images, then alignment accuracy is improved, but GCP position uncertainty propagates to ortho image error

Engineering Contradiction:

Improvealignment accuracyVSAvoidortho image accuracy

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent applies preliminary action by correcting GCP heights using DEM error calculations before performing bundle block adjustments. The method calculates DEM errors at GCP locations and adjusts GCP heights in advance, so that the subsequent ortho rectification process uses already-corrected control points, preventing error propagation to the final ortho image

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces DEM error calculation as an intermediary step between raw GCP data and bundle block adjustment. By computing the difference between actual GCP heights and DEM heights, the method creates a correction layer that mediates the transfer of positional accuracy from satellite imagery to ortho products

Inventive Principle:

Principle #24Intermediary (Mediator)

2Area of stationary object

If ortho rectification is performed using off-nadir satellite images, then mapping coverage is improved, but ortho accuracy deteriorates due to GCP uncertainty

Engineering Contradiction:

Improvemapping coverageVSAvoidortho accuracy

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by correcting GCP heights using DEM error calculations before performing bundle block adjustments. The method calculates DEM errors at GCP locations and adjusts GCP heights in advance, so that the subsequent ortho rectification process uses already-corrected control points, preventing error propagation to the final ortho image

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the height parameter of GCPs by applying DEM error corrections. By adjusting the vertical coordinate of control points based on the difference between actual and DEM heights, the method compensates for elevation-related positioning errors that would otherwise degrade ortho accuracy in off-nadir imagery

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20250377453A1Ground Control Point Height Adjustment for Improved Ortho Accuracy

Publication Date: 2025.12.11 VANTOR INC

AI summary

When generating ortho rectified imagery or products, DEM height error can result in distortions and ortho shift. Using satellite images taken from an off-nadir angle and adjusting them to be from an ortho perspective in particular creates building lean effects and other unwanted artifacts. By accounting for a DEM error, which is to say a difference in DEM height and GCP height, satellite images can be used to make images with improved ortho accuracy.