Ann Reg Sci (1999) 33:197±212 9 Location expression standards for ITS: Testing the LRMS Cross Street Pro®le Val Noronha1, Michael Goodchild1, Richard Church1, Pete Fohl2 1 Vehicle Intelligence and Transportation Analysis Laboratory, National Center for Geographic Information and Analysis, University of California, Santa Barbara, CA 93106-4060, USA (e-mail: noronha, good, church@ncgia.ucsb.edu) 2 ISERA Group, 5370 Hollister Ave a2, Santa Barbara, CA 93111, USA (e-mail: pete@isera.com) Abstract. Location can be expressed in a number of ways: coordinates, street addresses, landmark references, linear references, grid references, etc. The Cross Streets Pro®le is part of a location messaging speci®cation developed for use in Intelligent Transportation Systems (ITS). It describes a location essen- tially in terms of street names. This paper presents an evaluation of the Cross Streets Pro®le based upon lab and ®eld tests using commercial street network databases in the County of Santa Barbara. Results vary widely, depending upon database quality which in turn is dependent on geography (major streets vs minor streets, rural vs urban). Success rates can be improved with intelli- gent algorithms. Future directions to improve the quality of location messag- ing are discussed. Introduction A fundamental prerequisite to free exchange of geographic data is the ability to express a location, determined with respect to one map database, mean- ingfully with respect to another database. Location is always measured and expressed with respect to some frame of spatial or topological reference. A street address is explicitly relative, relying on named objects for orientation; even ``absolute'' latitude-longitude coordinates are expressed relative to a geodetic framework. Within a single database, locations can be expressed rel- ative to each other with great reliability. Consider a row of houses, for which coordinates have been captured using GPS. When overlaid on the street cen- terline, the houses may plot on di¨erent sides of the street due to inaccuracies in the house or centerline coordinates. Alternately the houses could be topo- logically linked to the centerline, as a set of left-side addresses and o¨sets. This relativistic representation skirts the coordinate inaccuracy problem, and is in- dependent of map scale. For a location to be portable to another database, location must be speci- All correspondence to Dr. Val Noronha, Department of Geography, UCSB, Santa Barbara, CA 93106-4060, USA