# Geo-DMP: A DTN-Based Mobile Prototype for Geospatial Data Retrieval  
[PERSON]  
1 School of Computer Science and Technology, Beijing Institute of Technology, Beijing 100081, China; 1 [EMAIL_ADDRESS] (C.L. ); [EMAIL_ADDRESS] (H.L. ); [EMAIL_ADDRESS] (R.G.) 1  
[PERSON]  
1 School of Computer Science and Technology, Beijing Institute of Technology, Beijing 100081, China; 1 [EMAIL_ADDRESS] (C.L. ); [EMAIL_ADDRESS] (H.L. ); [EMAIL_ADDRESS] (R.G.) 1  
[PERSON]  
2 Department of Computer Science and Technology, Tsinghua University, Beijing 100084, China 2*Correspondence: [EMAIL_ADDRESS] 2*Correspondence: xyong@mail.tsinghua. Along with the high value and importance of geospatial information being widely realized and the coming of the web 2.0 era, users are not only data consumers but also actively participate in the contribution of geospatial content. Such progression is conceptualized by scholars as \"Geospatial Crowdsourcing\" [6] or \"Volunteered Geographic Information\" [7]. Compared to conventional collection methods, in this case, expensive deployment and maintenance cost of sensory instruments can be saved, broader spatio-temporal coverage can be achieved, and more timely, detailed, and diversified data can be gathered. As it is a consensus that a significant portion of data generated in human day-to-day life is annotated with locational attributes [8, 9], with the aid of innumerable volunteers and a plethora of programmable sensors embedded inside mobile devices, we will gain further insights into the ambient environment from more perspectives, ranging from road traffic forecasting [10], culture heritage conservation [11], meteorological or climatological statistics [12], and environmental monitoring [13], to name just a few. However, currently, most geospatial-related applications are dependent on a centralized network infrastructure. Although lately, cellular network (3G/4G) and Wi-Fi are almost omnipresent, it still cannot be taken granted that they are always available for use. Firstly, natural catastrophes may incapacitate communication infrastructures and cause long-lasting outages [14, 15]. Secondly, in some densely populated situations, such as live concerts, sports matches, or large exhibitions, a burst of mobile clients may overload the cellular network and deteriorate network performance [16, 17]. Thirdly, a limited and costly data traffic budget, particularly in underdeveloped and developing countries, as revealed in Figure 2[18, 19], and the time-dependent pricing (TDP) strategies [20] cast influence on the attitude of subscribers towards data usage. Users possibly prefer to conserve a data quota or not enough data volume is left at the moment they need to access geospatial information. Lastly, although ever-growing Wi-Fi hotspots are deployed [21], looking for openly accessible ones is still no easy task, even in metropolitan areas [22]. Most discoverable access points are password-protected, and some enforce an authentication or registration via portals. Even if a user on-the-move is lucky enough to find a free usable AP, it is unable to serve persistent connections for him due to its finite radio coverage [23]. With all that in mind, it is quite reasonable that an alternative infrastructure-free method of acquiring and exchanging geospatial content is worth investigating. As a matter of fact, many past scholarly works have well documented feasibility proofs and practical means towards this goal. Above all, it is confirmed that users show a willingness to bear more patience on time-insensitive contents [24, 25]. In addition, multiple built-in short-range radio interfaces offer a novel way for mobile users to transmit contents between their devices directly. This device-to-device (D2D) [26]  
Figure 1: The global subscription number of mobile phone per 100 inhabitants. communication paradigm alleviates the reliance on infrastructures.