The study of structural lineaments is important for mineral exploration, geotectonic and geotechnical studies, flow and contaminant transport and for the mitigation of geologic hazards. This work deals with automatic extraction of lineaments from satellite imageries of different spatial resolutions as well as the analysis of these extracted lineaments. Wadi Bani Malik area located to the east of Jeddah city on the Red Sea coastal plain is chosen for this study. Six types of digital satellite imagery data were used, these are: Satellite imagery of low spatial resolution (LSR) including Landsat MSS of 80 m resolution, Landsat TM of 30 m resolution and Landsat TM of 25 m resolution; Satellite imagery of moderate spatial resolution (MSR) including Landsat ETM+ panchromatic of 15 m resolution and SPOT panchromatic of 10 m resolution; Satellite imagery of high spatial resolution (HSR) including the Indian Remote Sensing satellite IRS data of 5 m resolution. As expected, the analysis of the extracted lineaments from different data sets shows that the imagery data of HSR of the Indian IRS data gives the highest frequency of the extracted structural lineaments (N=3235), while the imagery data of LSR of the Landsat MSS data gives the lowest frequency of the extracted lineaments (N=89). The imagery data of MSR gives moderate frequency (N=1643) in average. It is recommended to use the imagery data of HSR and MSR for the extraction of structural lineaments for detailed and regional studies, respectively. The imagery data of LSR is not recommended for such studies; accordingly, it is not useful in the analyses of lineaments for geological purposes.
Lineaments are defined as "mappable, simple or composite linear features of a surface, whose parts are aligned in a rectilinear or slightly curvilinear relationship and which differs distinctly from the pattern of adjacent features and presumably reflect a subsurface phenomenon" . Extraction of lineaments from satellite imagery is important for many purposes such as geological mapping and mineral explorations  and seismic and landslide risk assessment . Lineaments may reflect surfaces of discontinuity in the rocks or may reflect a geological structures or topographic features or human made features. Lineaments are usually extracted and interpreted from satellite imagery manually or automatically. Wadi Bani Malik area is chosen to apply the automatic extraction techniques from digital satellite imagery of different resolutions. The area is located to the east of Jeddah city, Kingdom of Saudi Arabia, between Latitudes 21° 34' and 21° 37' N and Longitudes 39° 17' and 39° 21' E (Fig. 1).
The six satellite imagery subset data of different spatial resolutions (LSR, MSR and HSR) for the study area were used in this work. 4 and 6). These subsets of satellite imageries for the investigated area were enhanced and prepared as false color composite imageries for LSR or as black and white imageries for MSR and HSR (Figs. 2, 4 and 6). These imageries were used for automatically extraction of the lineaments.