## 3 Analytical Methods and Applications
### Geometric Measures  
This is the most basic form of geospatial analysis, dealing with distances and proximity of points, adjacency and connectivity. Because of their basic and fundamental nature, geometric measures find numerous applications in mobile location-based services [9,18,19]. These applications range from transportation to health, and from agriculture to sports. Figure 1 summarizes different application domains of IoT in mobile computing, together with the sensors and IoT devices employed at each case. Location-based sensing is an important element in almost all of these application domains, especially the ones of social interactions with people, transportation, health, agriculture, sports, participatory sensing and interaction between humans and physical things.  
Figure 1: The eco-system of location-based mobile phone IoT applications (Source: [9]).  
Distance and proximity have been considered in context-aware tourism recommendations [20] or location-based marketing [19], where marketing services could be offered to tourists and citizens based on their current location, e.g., nearby offers in restaurants and shops. Relevant application areas include mobile dating (_geo-social_ services), such as Grindr ([[https://www.grindr.com/](https://www.grindr.com/)]([https://www.grindr.com/](https://www.grindr.com/))) and Okcupid ([[https://www.okcupid.com/](https://www.okcupid.com/)]([https://www.okcupid.com/](https://www.okcupid.com/))), as well as gaming, such as the popular Pokemon Go (Niantic, Inc. [[https://poleemongolive.com/es/](https://poleemongolive.com/es/)]([https://poleemongolive.com/es/](https://poleemongolive.com/es/))). Moreover, distance and proximity are also highly relevant for managing infrastructures, e.g., in water utilities, for diagnosing problems in water distribution networks [21].  
UrbanRadar [13; 14] is an example of a location-based mobile application that interacts with IoT sensors deployed in the vicinity of the user, using online, global sensory directories to indirectly locate these nearby sensors. The concept of UrbanRadar is depicted in Figure 2. This approach can be combined with participatory or crowdsourced sensing for making environmental-related observations or for identifying emergency events [22; 23]. Examples include photographing diesel trucks to understand community exposure to air pollution [24], or measuring the personal exposure of citizens to noise in their everyday environment [25].  
In addition, adjacency is useful in disaster monitoring and response, such as monitoring landslide displacements [26] and deep-ocean tsunami occurrences [27].  
Further, the exact locations of events and the distances between them and other locations of interest are crucial for health geography and epidemiology studies, such as detection of infectious diseases [28]. The HealthMap project [29] analyzes such incidents to improve consumer education around disease risk at the local level and to encourage proper prevention practices. It offers various relevant services such as searching for locations offering flu vaccines or tracking geographic and temporal trends in infectious diseases among travelers, immigrants, and refugees.