Smartphone GNSS Accuracy Approaches Mapping-Grade Receiver Capabilities in Forest Conditions, and Submeter Accuracy may be Possible using an External Antenna

Abstract Using a tightly controlled, forested GPS test course located in Athens, Georgia, two smartphones, an iPhone 13 Pro (iOS) and Google Pixel 6 Pro (Android), were assessed to better understand their positional accuracy under different forest conditions and stand types. Additionally, a high precision external GNSS antenna was also assessed. With a focus on how professional foresters typically use their smartphones when collecting Global Navigation Satellite System (GNSS) data in the forest (i.e., single static position fixes, at approximate waste height, and with minimal wait times before collection), we found that, generally, the root mean square error (RMSE) (m) of both the iPhone 13 Pro and Google Pixel 6 Pro were statistically significantly different, with the Google Pixel 6 Pro outperforming the iPhone 13 Pro by 1 to 3 m in both an older natural loblolly pine ( Pinus taeda ) stand and in an older mixed upland hardwood stand under leaf-off and leaf-on conditions. Forestry professionals, on average, may expect between 2 to 6 m accuracy when using a smartphone in some southern forests. If one is capable of making an additional investment, a high precision external antenna that can be coupled with both iOS and Android devices at a cost comparable to mapping-grade GNSS receiver technology, may consistently achieve submeter accuracy in some forests without the need for real time kinematic (RTK) assistance. Awareness of the uncertainty associated with smartphones is important when incorporating these data into more advanced forestry applications.