Critique of: Automatic and Accurate Extraction of Road Intersections from Raster Maps by Yao-Yi Chiang · Craig A. Knoblock · Cyrus Shahabi · Ching-Chien Chen Vikram Reddy Donthi Reddy Toufong Vang CSCI 8715 September 20, 2011

Problem Statement Difficult to accurately and automatically extract road intersections from raster maps. Significance of Research  Spatial Data set for rasters does not include or identify road intersections. (Road intersections are object-based models.)  These features may be used to combine or process spatial data sets.  Developed a framework for accurate and automatic separation of specific object-based models from raster. Difficulty in Accomplishing  Maps are complex.  Computers have difficulty distinguishing map features and elements from one another.  Current methods require user input/intervention to process.

Contributions Major Contributions of the Research  Developed method for automatically extracting road data.  95% precision.  75% completeness.  Researchers’ method does not require prior knowledge of the map. Most significant?  95% accuracy + 75% completeness.  Automatic extraction of map data. Why?  Rapid development and integration of data where none may exist.

Key Concepts Chiang et al, 2009 Go from raster image of Tehran… (Google map.) …to hybrid map. (Google map + Tourist map.)

Key Concepts The Approach 1. Automatic Segmentation Raster Map 2. Extract and rebuild road layer 3. Identify road intersections and extract. Binary Map Road Layer Road Intersection Pts, connectivity, and orientation

Key Concepts Segmentation (remove background). Researchers premise: foreground colors has high contrast to background colors.

Key Concepts Preprocessing (extract road layers a and b). Rebuild road layer (c and d). ID and extract road data (e).

Validation Methodology Related Work Utilized related research and methods.  Segmentation process.  Road extraction and rebuild. Researchers’ Prior Work Localized template matching (LTM) (compare experiment results with original raster) The Experiment

Validation Methodology Verification of accuracy of process. Geometric Similarity (Lay term: how close is the extracted point from to the original point on the raster?) Evaluation

Critique Research assumption 1)Road lines are straight within small distances. 2)Linear structures are mainly roads. Falls apart when handling canals and other man-made non-road features.

Revisions? Framework  Straightforward.  Solid. Add…  Process for handling artificial map features that are not necessarily roads (e.g., canals)