Area Estimation Of Globally Carbonate Rock Outcrops In 2006 Based On Raster Map Vectorization

Recently,karst and rocky desertification have always been hot issues in the field of karst geological environment.Previous research reveal that soluble rock is essential to the development of karst.The main component of soluble rock is carbonate rock,which is about 70%.Rock outcrops in karst area will cause land degradation and rock desertification.Therefore,carbonate rock outcrops is one of the important factors causing rocky desertification.According to previous studies,the karst geology exhibited that carbonate rock in the lithosphere also have the function of carbon sinks.A detailed study of the global carbonate rock area is of great significance not only for karst,rocky desertification,and geological carbon sinks,but also for the research and development of related fields,such as carbonate oil and gas industry.The findings of karst researchers and geologists claimed that they confirmed the existence of karst carbon sinks phenomena and reflect global environmental changes sensitively.However,the role of geological carbon sinks has not yet been recognized by the “Inter-Governmental Climate Change Committee(IPCC)”.The vector map can easily extract,classify,and superimpose the various features on the map,which is beneficial to better analysis and study of geological carbon sinks.At present,the distribution of carbonate rocks is mostly presented in the form of printed geological maps rather than few vector data,which limits the correlation analysis of carbonate rocks.In this work,a vector map “Global Carbonate Rock Outcrops Area”(third edition)was employed as raw material,which was obtained from the University of Auckland.Other detailed data were also provided by the author Prof.Paul Williams via E-mails correspondence.We found the second edition of the map only presented a raster map,which exists in the form of book illustrations.As a result,it is not suitable for the analysis and research of carbonate rocks using efficient and modern information processing techniques.As a raster map vectorization analysis method,ArcGis was applied to the analysis of the global carbonate rock outcrops map(Revised in 2006)in Karst Hydrogeology and Geomorphology published by Ford & Williams(2007).And the estimated area the carbonate rock outcrops was achieved.Firstly,the control points of the raster map were selected by human-computer interaction,the global least-squares method was used to fit the correction model,and the local accuracy was optimized to achieve georeferencing;then,using human-computer interaction and automatic scanning to vectorize it and estimated area of the globally outcrops carbonate rock is approximately 17.9 million square kilometers,accounting for 13.5% of the land area.And the area is approximately 17.66 million square kilometers in the “Global Carbonate Rock Outcrops Area”(third edition)provided by Prof.Paul Williams.The estimated data based on the second edition of the raster map exhibit a satisfactory deviation(1.38%)compared to the reported one,further verifying the rationality of the method used in this study.In summary,an efficient raster map vectorization method is used to estimate the area of globally carbonate rock outcrops.This method provides a new technology for the acquisition of important geographic vector data in the era of electronic information;fills a blank in the research of carbonate rock.The method also provide a reference for similar type of data processing.An the obtained vector map data can also provide data resources for relevant studies of carbonate rock.