The progressive transmission of map data on the World Wide Web provides the user with a self-adaptive strategy to access remote data. It not only speeds up the web transfer but also offers an efficient navigation guide for information acquisition. The key technology in this transmission is the efficient multiple representation of spatial data and pre-organization on the server site. This paper aims at progressive transmission investigating some constraints from three aspects: data organization on server site, data control in the transmission process and data restore after reaching the client. Two strategies, namely on-line map generalization and off-line map generalization, are examined respectively for this kind of progressive transmission.
