Zebra Crossing Spotter: Automatic Population of Spatial Databases for Increased Safety of Blind Travelers - eScholarship (2015)

Zebra Crossing Spotter: Automatic Population of Spatial Databases for Increased Safety of Blind Travelers Dragan Ahmetovic Roberto Manduchi Universita degli Studi di Milano University of California Santa Cruz dragan.ahmetovic@unimi.it James M. Coughlan manduchi@soe.ucsc.edu Smith-Kettlewell Eye Research Institute Universita degli Studi di Milano coughlan@ski.org sergio.mascetti@unimi.it Sergio Mascetti ABSTRACT In this paper we propose a computer vision-based technique that mines existing spatial image databases for discovery of zebra crosswalks in urban settings. Knowing the loca- tion of crosswalks is critical for a blind person planning a trip that includes street crossing. By augmenting existing spatial databases (such as Google Maps or OpenStreetMap) with this information, a blind traveler may make more in- formed routing decisions, resulting in greater safety during independent travel. Our algorithm first searches for zebra crosswalks in satel- lite images; all candidates thus found are validated against spatially registered Google Street View images. This cas- caded approach enables fast and reliable discovery and lo- calization of zebra crosswalks in large image datasets. While fully automatic, our algorithm could also be complemented by a final crowdsourcing validation stage for increased accu- racy. Independent travel can be extremely challenging without sight. Many blind persons learn (typically with the help of an Orientation and Mobility, or OM needs to follow the route safely while being aware of his or her lo- cation at all times; and needs to adapt to contingencies, for example if a sidewalk is undergoing repair and is not acces- sible. Each one of these tasks has challenges of its own. In particular, the lack of visual access to landmarks (for exam- ple, the location and layout of a bus stop or the presence of a pedestrian traffic light at an intersection) complicates the wayfinding process. Thus, a straightforward walk for a sighted person could become a complex, disorienting, and potentially hazardous endeavor for a blind traveler. Technological solutions for the support of blind wayfind- ing exist. Outdoors, where GPS can be relied upon for ap- proximate self-localization, a blind person can use accessible navigation apps. While these apps cannot substitute proper OM I.4.8 [IMAGE PRO- CESSING AND COMPUTER VISION]: Scene Analy- sis—Object recognition; K.4.2 [COMPUTERS AND SO- CIETY]: Social Issues—Assistive technologies for persons with disabilities General Terms Algorithms, Human Factors Keywords Orientation and Mobility, Autonomous navigation, Visual impairments and blindness, Satellite and street-level im- agery, Crowdsourcing Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than the author(s) must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from Permissions@acm.org. ASSETS’15, October 26–28, 2015, Lisbon, Portugal. Copyright is held by the owner/author(s). Publication rights licensed to ACM. ACM 978-1-4503-3400-6/15/10 ...$15.00. DOI: http://dx.doi.org/10.1145/2700648.2809847 . INTRODUCTION http://mutcd.fhwa.dot.gov