goGPS is a software package designed to improve the positioning accuracy of low-cost GPS devices by relative positioning. The development of the MATLAB version started in 2007 at the Geomatics Laboratory of Politecnico di Milano, Como campus (Italy), under the supervision of Dr. Mirko Reguzzoni, as a Master thesis project (Dominioni, Teruzzi). It was then continued during two other Master theses (Colla; Palmulli, Tettamanti) and one Ph.D. thesis (Realini). goGPS code (MATLAB) was first published as open source software (GPL) in August 2009. Its development is now carried out mainly by GReD srl, with contributions from various teams at international level. The goGPS Java adaptation, started in 2011 and published here, was initially supervised, reviewed and developed by Cryms sagl. Now it is being carried on mainly by GReD srl and Yoshida Lab. of Osaka City University. The Java code is released under an LGPL license.