## 1 Introduction  
Tea is one of the most popular beverages worldwide. Different types of tea are cultivated and consumed, and green tea is one kind of tea favored by many people all around the world. Longjing tea is one of the most famous green teas in China and also one of China's protected geographical indication products. Longjing tea contains various nutritious compositions [1,2]. Indeed, the planting area of Longjing tea is large, and the exact producing area of Longjing tea is a determining factor influencing its quality and price [3]. The commercial value of Longjing tea varies according to harvest time,processing technique and procedure, and producing areas, and the price of expensive Longjing tea can be ten times that of the cheap ones. The geographical origins of Longjing tea relate to different climates, soil properties, water, etc.  
Due to the high commercial value of Longjing tea, adulteration of Longjing tea from different geographical origins is common. Traditionally, identification of geographical origins of Longjing tea is based on experienced tea farmers and tea experts or reagent based chemical analysis methods. Tea farmers and tea experts depend on personal experiences, such as observing the appearance as well as tasting and smelling the sensory properties. The chemical methods are reagent-wasteful, time-consuming, and require complex sample preparation and instrument operation [4; 5]. These methods are not suitable for on-line, real-time, and large-scale detection. Thus, rapid and non-destructive methods are needed.  
Visible/near-infrared spectroscopy (VNIRS) is widely used as a rapid and non-destructive technique for tea classification [6; 7; 8] and tea composition determination [9; 10; 11]. Hyperspectral imaging (HSI) is a technique integrating both spectroscopic techniques and imaging techniques, acquiring spectral and spatial information simultaneously. Traditional VNIRS acquires spectral information by 'point' scan or'spot' scan, so only the spectra of a small region within the sample are measured. HSI acquires spectral information from a predefined region of interest (ROI). In general, the entire sample region is defined as the ROI. HSI acquires more comprehensive information about samples. Hyperspectral imaging is widely studied in the fields of agriculture [12; 13], food [14], medical [15], and pharmaceutical [16], to name a few. Moreover, hyperspectral imaging is also studied in the tea industry for tea quality inspection [17; 18; 19].  
In general, a certain amount of tea samples (contains tens or more tea leaves in a sample) is used for VINRS and HSI analysis and overlap of tea leaves occurs in this situation [6; 7; 8; 9; 10; 17; 18; 19]. Thus it is difficult to identify adulterations in this amount of tea when some amounts of adulterations are mixed into the normal sample. With the advantages of HSI, spectral information of a single tea leaf on a large scale can be obtained and analyzed efficiently, making it possible to identify adulteration in tea by investigating single tea leaves. On the other, studying a single tea leaf can significantly increase the number of samples for analysis with larger variations in tea features.  
The goal of this study is to explore the feasibility of using hyperspectral imaging to identify the geographical origins of Longjing tea based on single tea leaves. The specific objectives were: (1) to explore the feasibility of using single tea leaf for identification of the geographical origins of Longjing tea; (2) to explore the differences of two different hyperspectral imaging sensors at two spectral ranges; and (3) to build classification models for identification of the geographical origins of Longjing tea.