This book constitutes the thoroughly refereed proceedings of the Third International Conference on Geographical Information Theory, Application and Management, GISTAM 2017, held in Porto, Portugal, in April 2017. The 11 full papers presented were carefully reviewed and selected from 70 submissions. The papers are centered around photogrammetry, spatio-temporal data acquisition, spectroscopy and spectroradiometry, hyperspectral imaging, Earth observation and satellite data, computational geometry, web applications, geographic information retrieval, urban and regional planning.