Remote Sensing-derived DEMs For Automatic Lineaments' Extraction: Impacts Of The DEM's Vertical Accuracy

Remote sensing data,such as satellite images,and remote sensing-derived Digital Elevation Models(DEMs)are credited by simplifying many geological processes that require laborious and costly fieldwork,such as lineaments extraction,tectonic geology,and river terrace extraction,etc.Over and above,the recent remarkable surge in the availability of Global DEMs from many free open sources,as well as their advantages over satellite imagery,have promoted and extended their wide application as remote sensing methods for automatic lineaments' extraction.The quality of a DEM impacts the results of its application,and this quality is mainly controlled by its vertical accuracy.And despite the common and increasing utilization of DEMs for the automatic extraction of lineaments as many preceding studies addressed it,these studies did not address the impacts of the DEM's vertical accuracy on the automatic lineaments' extraction results.Therefore,through the conducted research,we present the first study on the relationship between the vertical accuracy of the DEM and the automatically extracted lineaments from the utilized DEM.Where the presented dissertation addressed the following questions:(1)Whether the vertical accuracy of the employed DEM impacts the automatically extracted lineaments or not?(2)How could the utilized DEM vertical accuracy impact the extracted lineaments?(3)Why could the DEM vertical accuracy impact the automatically extracted lineaments?The research presents detailed qualitative and quantitative analyses of the impacts of the DEM's vertical accuracy on the automatic extraction results.The area around the city of Baoji,Shaanxi province,China,was selected as a study area,and the lineaments were automatically detected and extracted using the LINE algorithm of PCI Geomatica,based on the robust Canny algorithm,from two groups of DEMs.The first group of the employed DEMs comprised three 1? DEMs with different vertical accuracies: tri stereo ZY-3 imagery-derived DEM,SRTM1V3,and ASTGDEMV2,whereas the second group comprised two 3? DEMs with different vertical accuracies: tri stereo ZY-3imagery-derived DEM and SRTM3V4.The automatically extracted lineaments from both sets of the utilized DEMs were verified by true geological lineaments extracted from an existing geological map and were then geospatially analyzed in terms of their numbers,lengths,anddensities.Results of the research drew the following new findings:(1)The vertical accuracy of the employed DEM has significant impacts on the automatically extracted lineaments.(2)The SRTM1V3 has the highest vertical accuracy in the northern mountain area of Baoji among the 1” DEMs set followed by the ASTGDEMV2,whereas the ZY3DEM1 was the lowest accurate DEM attributed to the fact that the ZY3DEM1 was generated from tri-stereo ZY-3 images using the RFM based only on the RPCs without any GCPs,and this model is known to be biased when structured only on the basis of RPCs.Whereas in the 3”DEMs set,the SRTM3V4 has higher vertical accuracy than the ZY3DEM3.(3)The higher the vertical accuracy of the employed DEM,the higher the credibility of the extracted lineaments,and the greater the agreement between the automatically extracted lineaments and the true lineaments,where the lineaments extracted from the SRTM1V3 and SRTM3V4,which are the highest accurate DEMs in the 1” and 3” DEMs' groups,respectively,were the best-fitted to the true lineaments.Whereas the extracted lineaments from the ZY3DEM1 and ZY3DEM3,which are the lowest accurate DEMs in the 1” and 3”DEMs' groups,respectively,had the lowest agreement with the true lineaments.(4)The results of the extracted lineaments from both sets of the employed DEMs were consistent and showed the same new findings that the vertical accuracy of the applied DEM significantly affects the number,length,and density of the extracted lineaments.(5)There is a strong positive correlation between numbers,lengths,and densities of the automatically extracted lineaments and the vertical accuracy of the employed DEM,where these quantities remarkably increase with increasing vertical accuracy of the DEM.The research results are of great significance to the applications of the lineaments in terms of DEM data selection and quality evaluation.Where,in spite of the diverse availability of the DEMs from the freely available or open sources,the open sources only can provide DEMs with low to medium vertical accuracy whereas,the high-accuracy DEMs require much more cost.In this regard,the present study guides and helps in the trade-off between the quality of the extracted lineaments,as per the targeted application,and the required quality of the utilized DEM data,as per the available budget.