# Positioning Methods and the Use of Location and Activity Data in Forests
## 2 Types of Positioning Technologies
### Sns-Ref  
Individuals can share positioning information with one another locally through GNSS-RF networks (Figure 2, panel C), in which dedicated transponders or mobile devices determine coordinates using GNSS and then transmit those coordinates in short data bursts to other nearby devices via a radio frequency (RF) signal (Figure 4). GNSS-RF may be contained in a single unit, or GNSS-enabled devices like smartphones may be paired with miniaturized radios like goTenna(tm) or Bearttooth(tm) to relay location information in areas lacking cellular coverage (Figure 2, panel F). This method has been evaluated widely for off-the-grid location sharing in operational forestry [85; 86; 87; 20; 88; 21; 22].  
While quantifying the accuracy of single-user GNSS device applications described in previous sections is relatively simple, GNSS-RF and other systems that incorporate location sharing between multiple devices in remote areas pose different challenges for quantifying accuracy of position, navigation, timing, and other varieties of data among resources. This is due to the added impact of a temporal error component that sometimes interacts with spatial error and may be affected by other factors [21; 22; 23]. The temporal component becomes important in remote locations and data  
Figure 4: Example configuration for a real-time GNSS-RF network used in operational forestry to increase the safety and efficiency of logging operations. Each radio determines its coordinates using GNSS. Current positions of each piece of equipment, and possibly other data, are then transferred to other units via radio frequency at rates of typically one transmission per five seconds or less. One or more devices are attached (tethered) to tablets or other mobile devices to map the locations of all equipment in real time.  
sharing because user positions and the associated data are (1) received or calculated on the target user's device initially, and then (2) transmitted to other, neighboring devices. Most PNT research in natural resources has focused on error associated with the former component (target user location), and generally focused on static position accuracy. However, the latter process (regular transmission and sharing of locations from the primary device user to one or many neighbor devices) introduces time lag that is a function of both (a) the interval at which data packets are relayed between the devices and (b) transmission quality [21; 22; 85; 86]. For example, the locations of the forestry equipment shown in Figure 4 may be received and determined at intervals of 100 hertz (Hz) on smartphones or GNSS receivers. However, those locations are transmitted to other devices at intervals that are typically 1 Hz, but possibly as infrequently as 2 Hz (one set of coordinates every 30 s) or less. Thus, even when radio transmission is clear, there is up to a 30 s gap that occurs when the location and vector heading of any worker or piece of equipment is unknown, from the perspective of those viewing activities on the mobile screen of a secondary device on the network. If a single transmission of coordinates (latitude, longitude), direction, and speed is missed due to topography or other interferences, that period of mapping uncertainty about the target user's location and path increases to one minute, and so forth. This compounded error that includes spatial and temporal components is important for mission critical safety and health applications [21; 22; 87; 23], particularly when we consider GNSS-RF as the basis for first responder life safety applications and heavy equipment automation.