# Positioning Methods and the Use of Location and Activity Data in Forests
## 2 Types of Positioning Technologies
### GNSS--Smartphone and Tablet-Based Mapping  
While the dedicated GNSS devices described in the previous section were ubiquitous in natural resources until recent years, positioning via the GNSS chip present in most modern mobile devices and tablets is now increasingly common [55; 56; 57]. Mobile-based apps such as Avenza Maps(r) store georeferenced, custom maps in GeoTIFF or GeoPDF format on mobile devices, allowing users to view  
Figure 2: Common types of available technologies for real-time location sharing in remote areas. A. Conventional handheld GNSS receiver displays the user’s location. B. Two-way satellite communication using Iridium or other commercial satellite communication networks make it possible to send emergency SOS signals or text messages relayed through the communications satellite. C. GNSS transponders paired with radio frequency (RF) transmission (GNSS-RF) send locations between devices, so that location coordinates can be mapped on phones or tablets connected to receiving devices that are within radio line-of-sight. D. Advanced data radios with mesh networking function the same as (C), but in this case each radio (node) serves as a repeater, improving network connectivity around topographic or other obstacles in remote areas. E. GNSS-enabled watches transmit user location, inertial sensor and other sensor data (e.g., heart rate) to the user’s phone using Bluetooth, Bluetooth Low Energy (BLE) or ANT wireless. F. Miniaturized radios that pair with smartphones using Bluetooth or BLE provide the same capabilities as (D) but utilize the existing GNSS chip in phones providing location sharing functionality at lower costs than dedicated radios.  
positions on a smartphone or tablet rather than on a conventional, dedicated GNSS unit [58; 59]. The United States Department of Agriculture (USDA) Forest Service, United States Geological Survey (USGS), and many other federal and state agencies, as well as private forest industry landowners, increasingly make GeoPDF map files available to the public or contractors for use with mobile-based mapping apps [60]. These applications rely only on the satellite-derived GNSS coordinates received by the device and display the user's location on a locally-saved version of a map file [61]. They therefore require neither cellular service connectivity nor WiFi for mapping and are thus fully functional in remote areas given map files are downloaded to the device in advance. This approach of alternating between online and offline data collection paired with GNSS-based location information on smartphones and tablets has been used widely in operational forestry and more recently in research applications such as mapping beetle outbreaks [62] and landslide hazard mapping [57].  
GNSS accuracy of modern smartphones is approximately 2 m in open conditions and ranges from about 4.5 to 6.7 m (leaf-off) and 6.7 to 11.5 m (leaf-on) in mixed deciduous-coniferous forests [29]. Accuracy varies by brand and model, but devices supporting both GPS and GLONASS are generally able to achieve higher accuracies under forest canopies [29].