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Model Perspective
Model Perspective
Dec 21, 2025 · Fundamentals

Why Did Nanjing’s GPS Fail? Unveiling the Math Behind Satellite Navigation

On December 17, 2025, a massive GNSS signal disruption in Nanjing caused major navigation apps to fail, prompting a technical analysis that reveals how trilateration, pseudorange measurements, linearization, least‑squares solving, and error factors like GDOP and carrier‑phase ambiguity underpin modern satellite positioning.

Carrier PhaseGDOPGNSS
0 likes · 9 min read
Why Did Nanjing’s GPS Fail? Unveiling the Math Behind Satellite Navigation
Model Perspective
Model Perspective
Nov 8, 2022 · Fundamentals

Mastering Multiple Linear Regression: Theory, Estimation, and Prediction

This article explains the fundamentals of multiple linear regression, covering model formulation, least‑squares estimation of coefficients, statistical tests for significance, and how to use the fitted equation for accurate predictions and confidence intervals.

Least SquaresMultiple Linear RegressionPrediction
0 likes · 5 min read
Mastering Multiple Linear Regression: Theory, Estimation, and Prediction
Model Perspective
Model Perspective
Sep 15, 2022 · Fundamentals

How to Build and Apply the GM(2,1) Grey Model for Accurate Forecasting

This article introduces the GM(2,1) grey model, presents its definitions and theorem, walks through a step‑by‑step case study with data preparation, parameter estimation, solution of the differential equation, and shows how to implement the whole process in Python with code examples and error analysis.

GM(2,1)Grey ModelLeast Squares
0 likes · 7 min read
How to Build and Apply the GM(2,1) Grey Model for Accurate Forecasting
Model Perspective
Model Perspective
Jul 12, 2022 · Fundamentals

How Simple Linear Regression Uncovers Hidden Relationships in Data

This article explains the theory and practice of simple linear regression, covering deterministic vs. stochastic relationships, the least‑squares estimation of coefficients, goodness‑of‑fit measures such as R², hypothesis testing for linearity, and a real‑world case linking wine consumption to heart‑disease mortality.

Least SquaresR-squaredStatistical Modeling
0 likes · 8 min read
How Simple Linear Regression Uncovers Hidden Relationships in Data
Model Perspective
Model Perspective
Jun 2, 2022 · Fundamentals

Understanding Simple and Multivariate Linear Regression Models

This article introduces the basics of simple (univariate) linear regression and extends to multivariate linear regression, explaining their regression equations, the use of the least‑squares method to estimate parameters, and the practical relevance of multiple predictors in modeling real‑world phenomena.

Least Squaresmachine learningmultivariate analysis
0 likes · 3 min read
Understanding Simple and Multivariate Linear Regression Models