You could almost say that María Teresa Ruiz-Monzón (Vitoria-Gasteiz, Basque Country, 1988) carries the mountain around in her pocket. The slopes, spurs and drops of this mountain are very realistically represented on the mobile phone of this student who has recently graduated in Computer Sciences at the University of the Basque Country (UPV/EHU). This was in fact her end-of-studies project: to develop an application to be able to use 3D geolocation on android smartphones. “It resembles Google Earth, but has a more specific purpose,” she explains. It has been devised for mountaineers so that when it is foggy they can find their way by looking at their mobile phone screens. When the horizon is fuzzy, ordinary maps cannot really help us to position ourselves or to know whether we could be getting too close to a precipice. This 3D application is designed to meet these needs. Ruiz has had to combine different knowledge, systems and all kinds of data to be able to develop her project. Apart from mastering Android, she has had to incorporate into it certain programs that are compatible with it, like OpenGL ES (graphic programming interface), LaTeX (text processing system) and Shapefile (geodata file format). She has also learnt from videogames to draw the 3D surfaces, and has obtained relief maps and other geographical data on the Basque Autonomous Community (region) over the website of the Government of the Basque Autonomous Community. But it is not enough just to gather the most detailed maps; the application has to know where the user is and therefore which map to display to him or her. For this purpose, this computer scientist has made use of the electronic compass available on smartphones: “I use the compass like a camera. I detect which way the phone is looking and I draw the surface existing on that stretch of terrain so that he or she can see what is there.” Ruiz explains that it has been no easy task creating the surface, managing all the information, detecting the location and managing to download the right files on the basis of all this. But the biggest difficulties were caused by the limited memory capacity of mobile phones: “A lot of information has to be managed and the most difficult thing was to enter all this without exceeding the memory limits of mobile phones.” Naturally, this tool needs the Internet to make the appropriate geolocation consultations at each moment, and downloading such large files (running to several Mbytes) over the Internet can take quite a time. To prevent the application crashing in situations like this, Ruiz has been developing a mechanism; it still needs to be improved further, but it is progressing nicely. “The downloads are done in background mode, so the application can go on working even though not all the files may be available. This is so that you can go on using your mobile during the download, too," she explains. In any case, it has to be remembered that in the mountains mobiles often end up out of range and in these cases the Internet cannot be used. For this very reason this application has the option of using it without a connection. But in this case, you have to do your homework before setting off: “If you download the files beforehand at home and on a card, it can be done.” Now that Ruiz has had her viva on her end-of-studies project, she has completed her degree in Computer Sciences but is planning to go on developing the application she has created. “Some minimal improvements have to be made, but I think there could be a possibility of marketing it. I don’t yet know whether I will sell it, whether I will release the code... But there are possibilities. I’ll see,” she says.