Inthis paper we report a new application of digital photogrammetry.Itreflects ourrecentattempttoward the developmentofthe field of photo ecometrics. We illustrate the potential of digital photogrammetry in the monitoring of changes ofoak woodland of California using 1∶12

000 scanned aerial photographs.The photographs were taken in 1970 and 1995 .Stereopairsin 1970 and 1995 have been usedto derive digitalsurface models（DSM） thatcontain 3Dmorpho logicalcoordinates of everylandscape componentincluding oak wood

grassland and buildings.The DSMs allow us not only to studychanges ofcanopy closure butalsoto measuretree heightsand heightchange duringthe25 yearperiod .The potentialof DSMopens many opportunities for improving the accuracy of change detection and species recognition than solely usingtraditional multispectral analysis.