Background: This article reports on an evaluation study of a project seeking to develop the use of position-linked datalogging with primary pupils in environmental science contexts. Purpose: The study sought to find out the extent to which the project had developed: (1) participant teachers' confidence in using datalogging as an everyday part of their science teaching; (2) pupils' abilities to collect and interpret relevant environmental monitoring data; and (3) the use of scientific data within environmental education in the project schools. Programme description: The project used software which integrates data from Global Positioning System (GPS) with sensor data collected outdoors to produce Google Earth visualisations of environmental quality in each school's locality. Sample: Phase 1 involved 10 primary schools in the South West of England (2008-9), and phase 2 was implemented in six primary schools in Greater London during 2010. All pupils in the 9-10-year-old age range participated to some extent (N [approximately equal] 450) and each school identified a focus group of between two and four pupils (n = 38) together with two members of staff (n = 32) to be more closely involved in the project. Design and methods: The evaluation adopted a multi-method approach, drawing upon documentary sources (n = 40); observations of continuing professional development (CPD) cluster days (n = 8) and dissemination events (June 2009 and January 2011): baseline pupil assessment tasks (n = 291) and teachers' baseline questionnaire (n = 25) in September 2008 and March 2010; classroom observations; samples of pupil work (n = 31); end-of-project pupil assessment (n = 38) and teachers' and pupils' responses to the project (n [approximately equal] 180) in June 2009 and December 2010; and a longitudinal evaluation in February 2012. Results: Datalogging had become a regular feature of practical science in nearly all project schools up to 30 months after the end of the project, but the use of position-linked logging had not been sustained. While there is evidence of pupils developing a range of scientific enquiry skills through the project, the extent to which their interpretation of data improved is unclear. All participating schools made greater use of scientific data than before the project to develop their environmental education. Conclusions: The project has demonstrated the potential of combining datalogging with GPS technology to support challenging, motivating and relevant scientific enquiry. Primary teachers require targeted technical and pedagogical support to maximise learning benefits for pupils. (Contains 2 tables.)