关于ArcCatalog calculate statistics 关于GLOPEM NPP

<P>我下载了 GLOPEM NPP数据，可是显示出来的值正好和实际相反，也就是说本应高的地方反而低。查阅说明文件之后是这样的“When the GLOPEM NPP images are opened in ArcGIS, the minimum and maximum values appear to be anomolously high and low. The reason for the anomolously high and low NPP values when opened in ArcGIS is because ArcGIS does not automatically calculate statistics on images. The user will need to go into ArcCatalog and build statistics for the imagery that needs to be loaded. ” 请高手指点一下啊，不胜感激<BR></P>