Hyperspectral target detection is based on the spectral characteristic difference between the target and the background.Generally,the finer the resolution is,the higher the accuracy will be. Yet the spatial and spectral resolution can barely meet the need simultaneously,for technical obstacles. A tradeoff between the two factors is needed for effective target detection and the choice of appropriate remote sensing data for target detection has always been concentrated nowadays. Most previous studies focused on the precision assessment of the target detection in a particular case using current image spectrometer data,but failed to provide a quantified criterion for either the spatial or the spectral resolution appropriate for the data in that case. This study focused on the quantification of the scale impact of spectral and spatial resolution on target detection precision,with respect to situations where the target is small and has a similar spectrum to the homogenously distributed background.Here we proposed a technical method for spectral and spatial resolution assessment for target detection,setting green context and sparse grass as the target and background,respectively. Through the down sampling processing of the high spatial hyperspectral image from Field Imaging Spectrometer System（ FISS） together with Constrained Energy Minimization（ CEM） detection algorithm and Receiver Operation Characteristic（ ROC） evaluation method,this study analyzed the relationship between the spatial and spectral resolution and the detection accuracy. And then it proposed the optimal spatial and spectral scale for target detection.Results revealed that:（ 1） With the decline of spatial resolution,the detection accuracy experienced three stages of descending rates: gently-dramatically-gently. The corresponding spatial resolution before the second stage is the effective scale for detection. Using FISS data（ 4—7 nm spectral resolution and 1. 4 nm sampling interval）,the required spatial resolution for target detection was about within twice the size of the target;（ 2） When the spectral resolution was finer than 40 nm,two main features: the reflection peaks and basic trend differences,associated with the target and the background,could be identified. The detection accuracy would reach 0. 94 or above within the spatial resolution of 0. 85 cm. When the spectral resolution was coarser than 40 nm,the differences of reflection peaks disappeared since they were 20 nm apart and the detection accuracy decreased;（ 3） Given spectral resolution insufficiency（ > 40 nm）,the basic R,G,B bands added the yellow and red edge bands appeared the optimal combination for target detection with respect to current multispectral remote sensors.It was concluded that the quantitative analysis method and results of spatial and spectral scales for target detection would be of great significance for both data source selection and studies on other target-background combinations under similar conditions.

hyperspectral;target detection;spatial resolution;spectral resolution;scale effect;suitable scale