The work discussed in this paper aims to develop a Geographic Information System (GIS) to hold and display environmental and archeological data for the analysis of an inter-tidal zone. Langstone Harbour on the south coast of Hampshire, England, forms the study area. The work is being carried out with the support of The Royal Society for the Protection of Birds (RSPB) and Hampshire County Council. As it was found that existing topographic mapping would not provide a suitable topographic base for such an inter-tidal area, metric aerial photography and analytical photogrammetry were employed to create a detailed topographic base. The photogrammetric models were fitted within a control network established using a high precision differential Global Positioning System (GPS). Recorded three dimensional coordinates of archaeological finds and structures will allow the comparison between environmental and locational contexts of coastal archaeological structures. This will greatly enlarge the available archaeological data set, adding value to the data, as well as assisting the study of sea level change and wider coastal processes. Conversion and integration of other environmental data is adding further data layers of the GIS.