Accuracy of rectification using topographic map versus GPS ground control points

Reliable assessments of landscapes are needed for natural resource conservation and preservation efforts and for understanding the impacts humans are having upon those resources. Remotely sensed data provide an integrated view of the landscape and are nicely suited for temporal change studies. Reliable interpretation of Earth surface characteristics relies largely on accurate rectification of the remote sensing imagery to a map projection and on subsequent thematic classification. For rectification, ;l e found that control points acquired using the Global Positioning System (GPS) were superior to those acquired from digitized topographic maps. Differentially corrected GPS locations provided for the optimum rectification of SPOT satellite imagery while marginally better rectifications were obtained for Landsat MSS imagery using uncorrected GPS positions. Accuracy of ground control point sources for rectification should match the resolution of the digital image. Shifts in pixel digital number locations following the resampling procedure in rectification indicate a substantial amount of change might erroneously be attributed to change when, in fact, it might simply be due to differing methods of determining cartographic coordinates of ground control points. This has important implications in change detection studies and should be explored further.