I. INTRODUCTION  
II. BACKGROUND  
A. Problem Formulation and Symbols Definition  
B. Challenges of Monocular Re-Localization  
C. Comparison with Other Surveys  
III. GEO-TAGGED FRAME MAP  
IV. VISUAL LANDMARK MAP  
V. POINT CLOUD MAP  
VI. VECTORIZED HIGH-DEFINITION MAP  
VII. LEARNT IMPLICIT MAP  
VIII. BENCHMARKING MONOCULAR RE-LOCALIZATION  
IX. OPENING DISCUSSION  
A. Are Explicit 3D Models Necessary in Visual Localization?  
B. How to Select Specific Localization Method?  
C. What’s Next for Visual Localization?  
X. CONCLUSIONS