## 2 Materials and Methods
### Trauma and Injury Severity Scoring for the Probability of Survival Prediction
As characters (sentences) arrive from in the GPS receiver, these are buffered, and the parser will detect when a complete sentence has been provided, and the sentence gets broken down into its respective elements to retrieve the required values such as position coordinates. The kind of information that can be extracted from the parser depends on the GPS/GNSS receiver module. Almost all GPS/GNSS modules on the market support basic sentences, which are GGA (GPS Fix Data), RMC (Recommended Minimum Data), GSA (Overall Satellite data), GSV (Detailed Satellite data), GLL (Latitude/Longitude data), and VTG (Vector Track and Speed over the Ground). These are the standard structures that are commonly used in an application, and most of the information related to location, speed, direction, time, and navigation could be retrieved. It is also possible to use the GPS coordinates to gather all the terrestrial and demographic information using a third-party library like RTKLIB. The GPS information only provides the location coordinates, though these have to be mapped and aligned according to the geographical mapping system. RTKLIB OSM is an open source GNSS toolkit for performing precise positioning. It was possible to determine the position, using a GNSS receiver. The software supports all major satellite constellations (GPS, GLONASS, Galileo, and others) and it uses standard file exchange formats. The toolkit can be used on Windows and Linux platforms [51]. A number of GPS receivers provided raw measurements (carrier phase and code pseudo range), which were compatible with RTKLIB. The library was then used to calculate precise positioning to centimeter-level accuracy positioning. The most affordable were the single frequency receivers. The dual frequency receivers were more expensive, but they had higher accuracy, especially for baselines that were longer than about 50 km; the advantage was much less pronounced in sub-km baselines [51]. The GPS coordinate information, along with the GIS mapping tools, was used to locate the nearest healthcare service provider. The following steps were carried out to achieve this: The road graph plugin in QGIS was used for this task to load road layers for a geographical area in UK. Using the coordinates of the healthcare service providers in the nearby area, these were overlaid as layers. The start point layer became the current GPS coordinates and the end-point layers were the coordinates to the nearby healthcare service providers. Then, using the network analysis tool in QGIS, the shortest path to the nearest healthcare service provider was calculated, and the center information was retrieved. The shortest route to the center was traced according to the road graph-mapping layer. The GIS data was provided by Geofabrik [52]. The GPS/GNSS-based current position location, and the network analysis tool were used to calculate the shortest path between the current location and an end-point, which could potentially be a healthcare center. For calculating the shortest path from within an application, the following steps were carried out:  
1. To match geographical maps with GPS coordinates;
2. To generate a heatmap of the roads traveled, based on GPS track recordings;
3. To download road map data from an online repository of shapefiles and transform it into a network of roads;
4. To store the road network in a database;
5. To generate own records of journeys using a GPS tracking device log of the route traversed;
6. To implement a map-matching algorithm to match GPS track recordings to an existing road network using shapefiles. Matching GPS data against a map: A GPS receiver/logger captures a series of latitude and longitude coordinates over time and traces the path of someone moving from place to place. The GPS coordinates are recorded and stored according to the person's movements. Commonly available GPS devices enable the recording of a journey that is taken on foot or by a vehicle, by recording a series of coordinates.