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The information unavailability of a global navigation satellite system (GNSS) for geo‐localization in many military and tourism applications implies the need to employ other applicable types of information, such as automatic image‐based location recognition. Unlike most existing localization methods that use GNSS information to locate an initial position, this paper proposes an automatic geo‐localization framework that does not require GNSS data. The proposed framework is a two‐stage pipeline that uses a query image and digital elevation model (DEM) data as input. The authors frame automatic geo‐localization without GNSS recordings as a skyline matching problem. By extracting the skyline from the DEM data and query images, the query image can be localized by matching the query skyline feature to the DEM skyline database. It has been demonstrated that this low‐cost approach can perform efficiently in mountainous or hilly areas to produce reliable localization results. The system was tested on 50 testing site points within a large‐scale area (China, 202.6 km2), and an average position error of 43.13 m was detected within 4.5 s. [ABSTRACT FROM AUTHOR]

• Essential oil profiles were obtained from four Hypericum species. • H. bellum and H. perforatum demonstrated neuroprotective activity. • H. hookerianum and H. bellum oil showed strong antibacterial activity. • H. perforatum collected in Wushan showed tyrosinase inhibition activity. • The study provided a scientific basis for future exploration of Hypericum species. St. John's wort (Hypericum perforatum) is a well-known medicinal plant often used to treat mild to moderate mental depression. In southwest China, four species of Hypericum including H. perforatum , H. hookerianum , H. bellum and H. pseudohenryi have been used as traditional medicines for skin care, such as healing wounds, burns, and snake bites by local people. Hypericum volatile oils of these four species were obtained by supercritical CO 2 extraction and analyzed by GC–MS. From H. perforatum , 56 compounds were identified, the amounts of marker components are different between two collection sites. From H. hookerianum , 71 compounds were identified, mainly comprised of alkanes. From H. bellum , 43 compounds were identified, and its essential oil contains mainly oxygenated sesquiterpenoids. From H. pseudohenryi , 57 compounds were identified, and the essential oil has relatively high levels of alkanes. Because Hypericum species are used traditionally to treat depression, wounds, and other skin problems, their volatile oils were evaluated in vitro for neurite outgrowth-promoting, neuroprotective, antimicrobial, and enzyme inhibitory activities. H. bellum and H. perforatum from Wushan demonstrated significant neurite-promoting and neuroprotective activity. The Gram-positive Staphylococcus aureus ssp. aureus was inhibited by most of the tested oils. Sesquiterpenoids and alkanols are the most abundant constituents of H. hookerianum and H. bellum oils which showed strong antibacterial activity and help to explain the observed antimicrobial activity of the oil. H. perforatum collected in Wushan showed tyrosinase inhibition activity. Based on the current results, three Asian Hypericum species and two Chinese H. perforatum populations may be promising ingredients for cosmetics, foods, and pharmaceuticals. [ABSTRACT FROM AUTHOR]