{"@context":"https:\/\/schema.org\/","@type":"ScholarlyArticle","@id":"#article9685","name":"Computing the Fr\u00e9chet Gap Distance","abstract":"Measuring the similarity of two polygonal curves is a fundamental computational task. Among alternatives, the Frechet distance is one of the most well studied similarity measures. Informally, the Fr\u00e9chet distance is described as the minimum leash length required for a man on one of the curves to walk a dog on the other curve continuously from the starting to the ending points. In this paper we study a variant called the Fr\u00e9chet gap distance. In the man and dog analogy, the Fr\u00e9chet gap distance minimizes the difference of the longest and smallest leash lengths used over the entire walk. This measure in some ways better captures our intuitive notions of curve similarity, for example giving distance zero to translated copies of the same curve.\r\n\r\nThe Fr\u00e9chet gap distance was originally introduced by Filtser and Katz (2015) in the context of the discrete Fr\u00e9chet distance. Here we study the continuous version, which presents a number of additional challenges not present in discrete case. In particular, the continuous nature makes bounding and searching over the critical events a rather difficult task.\r\n\r\nFor this problem we give an O(n^5 log(n)) time exact algorithm and a more efficient O(n^2 log(n) + (n^2\/epsilon) log(1\/epsilon)) time (1+epsilon)-approximation algorithm, where n is the total number of vertices of the input curves. Note that for (small enough) constant epsilon and ignoring logarithmic factors, our approximation has quadratic running time, matching the lower bound, assuming SETH (Bringmann 2014), for approximating the standard Fr\u00e9chet distance for general curves.","keywords":["Frechet Distance","Approximation","Polygonal Curves"],"author":[{"@type":"Person","name":"Fan, Chenglin","givenName":"Chenglin","familyName":"Fan"},{"@type":"Person","name":"Raichel, Benjamin","givenName":"Benjamin","familyName":"Raichel"}],"position":42,"pageStart":"42:1","pageEnd":"42:16","dateCreated":"2017-06-20","datePublished":"2017-06-20","isAccessibleForFree":true,"license":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/legalcode","copyrightHolder":[{"@type":"Person","name":"Fan, Chenglin","givenName":"Chenglin","familyName":"Fan"},{"@type":"Person","name":"Raichel, Benjamin","givenName":"Benjamin","familyName":"Raichel"}],"copyrightYear":"2017","accessMode":"textual","accessModeSufficient":"textual","creativeWorkStatus":"Published","inLanguage":"en-US","sameAs":"https:\/\/doi.org\/10.4230\/LIPIcs.SoCG.2017.42","publisher":"Schloss Dagstuhl \u2013 Leibniz-Zentrum f\u00fcr Informatik","citation":"http:\/\/www.utdallas.edu\/~bar150630\/gap.pdf","isPartOf":{"@type":"PublicationVolume","@id":"#volume6280","volumeNumber":77,"name":"33rd International Symposium on Computational Geometry (SoCG 2017)","dateCreated":"2017-06-20","datePublished":"2017-06-20","editor":[{"@type":"Person","name":"Aronov, Boris","givenName":"Boris","familyName":"Aronov"},{"@type":"Person","name":"Katz, Matthew J.","givenName":"Matthew J.","familyName":"Katz"}],"isAccessibleForFree":true,"publisher":"Schloss Dagstuhl \u2013 Leibniz-Zentrum f\u00fcr Informatik","hasPart":"#article9685","isPartOf":{"@type":"Periodical","@id":"#series116","name":"Leibniz International Proceedings in Informatics","issn":"1868-8969","isAccessibleForFree":true,"publisher":"Schloss Dagstuhl \u2013 Leibniz-Zentrum f\u00fcr Informatik","hasPart":"#volume6280"}}}