SPIE Proceedings [SPIE Geoinformatics 2008 and Joint Conference on GIS and Built Environment: Monitoring and Assessment of Natural Resources and Environments - Guangzhou, China (Saturday 28 June 2008)] Geoinformatics 2008 and Joint Conference on GIS and Built Environment: Monitoring and Assessment of Natural Resources and Environments - Comparison analysis of agricultural land gradation evaluation based on different weight making methods