Positional accuracy of the Wide Area Augmentation System

Global Positioning Systems devices are increasingly being used for data collection in many fields. Consumer-grade GPS units without differential correction have a published horizontal accuracy of approximately 10 to 15 meters (average error). An attractive option for differential correction for these GPS units is the Wide Area Augmentation System (WAAS). Most consumer-grade GPS units on the market are WAAS capable. According to the FAA, the WAAS broadcast message provides integrity information about the GPS signal as well as accuracy improvements which are reported to improve accuracy to 3 to 5 meters. However, limited empirical evidence has been published on the accuracy of WAAS-enabled GPS compared to autonomous GPS. Results are presented of an empirical study comparing the horizontal and vertical accuracy of WAAS corrected GPS and autonomous GPS under ideal conditions using consumer-grade receivers. Data were collected for thirty minute time spans over accurately surveyed control points. Metrics of median, 68th and 95th percentile, RMSE and average positional error in x, y and z were computed and statistically tested with a hypothesis test. There was no statistical difference found between WAAS and autonomous position fixes when using two different consumer-grade units. A statistical difference was evident in a third unit type tested. Analysis of data collected for a twenty seven hour time span indicates that while WAAS is altering the estimated position of a point compared to autonomous position estimate, WAAS augmentation actually appears to increase the positional error

Evaluating GPS Effectiveness for Natural Resource Professionals: Integrating Undergraduate Students in the Decision-Making Process

Undergraduate students pursuing a Bachelor of Science in Forestry (BSF) degree at Stephen F. Austin State University (SFA) attend an intensive 6-week residential hands-on instruction in applied field methods. For students pursuing the BSF degree knowing the exact location of a forestland is crucial to the understanding and proper management of any related natural resource. The intensive 6-week instruction includes teaching how to use the Global Positioning System (GPS) to accurately record the spatial location of an earth’s surface feature. After receiving hands-on instructions during the summer of 2014, students were taken to the field to collect real-world locations. Students compared two different GPS units within a forested setting and learned that the consumer-grade Garmin eTrex 30 was more precise than the Garmin eTrex Legend HCx. Overall objective was to validate the effectiveness of SFA’s hands-on instructional methodology and to integrate undergraduate students in the decision making process of deciding which GPS unit a forester or natural resource manager should use to mark the spatial location of a natural resource. This study demonstrated that incorporating undergraduate students within a field-based research project preceded by hands-on instruction methodology enhances their undergraduate education and produces a more well-rounded society ready forester

Quantifying Natural Resources Using Field-Based Instruction and Hands-on Applications

Undergraduate students pursuing a Bachelor of Science in Forestry (BSF) degree at Stephen F. Austin State University (SFA) attend an intensive 6-week residential hands-on instruction in applied field methods. For students pursuing the BSF degree knowing the exact location, length, or area of a forestland is crucial to the understanding and proper management of any related natural resource. The intensive 6-week instruction includes teaching how to use the Global Positioning System (GPS) to accurately record the true spatial location of an earth’s surface feature. After receiving hands-on instructions during the summer of 2013, students were taken to the field to collect real-world locations and area measurements. Upon returning from the field students were instructed how to assess the accuracy of their GPS collected waypoints by deriving the Root Mean Square Error (RMSE) comparing their GPS collected locations, derived perimeter and area assessments with the actual location, length and area respectively. Overall objective was to assess the effectiveness of GPS hands-on instruction methodology within a field-based setting. Since accurate quantitative data are crucial in any natural resource management plan, a student being able to accurately assess the real-world location and derived GPS perimeter and area measurements is essential

Validating One-On-One GPS Instruction Methodology for Natural Resource Area Assessments Using Forestry Undergraduate Students

Undergraduate students pursuing a Bachelor of Science in Forestry (BSF) at Stephen F. Austin State University (SFA) attend an intensive 6-week residential hands-on instruction in applied field methods. The intensive 6-week instruction includes learning how to use the Global Positioning System (GPS) with a Garmin eTrex HCx GPS unit to accurately calculate area. Students were instructed how to assess the accuracy of their GPS collected waypoints by calculating the Root Mean Square Error (RMSE) comparing their GPS collected area measurements with instructor on-screen digitized area. Student’s average area RMSE between digitized and GPS derived area was 0.015 hectares, whereas instructor’s average area RMSE between digitized and GPS derived area was 0.015 hectares. Over 76% of students measured GPS area was within 5% of instructor on-screen digitized area. No difference between the students and instructors area RMSE of 0.015 hectares and high level of agreement between student measured GPS area and instructor on-screen digitized area: (1) indicates students receiving hands-on instruction in GPS applications can record accurate area measurements after only a limited 2 hour introduction; (2) the accuracy of the Garmin eTrex HCx GPS unit is not user dependent; and, (3) validates the interactive hands-on instruction methodology employed at SFA

Location Gathering: An Evaluation of Smartphone-Based Geographic Mobile Field Data Collection Hardware and Applications

Mobile field spatial data collection is the act of gathering attribute data, including spatial position, about features in a study area. A common method of field data collection is to use a handheld computing device attached to a global navigation satellite system in which attribute data are directly inputted into a database table. The market for mobile data collection systems was formerly dominated by bulky positioning systems and highly specialized software. However, recent years have seen the emergence and widespread adoption of highly customizable and user-friendly mobile smartphones and tablets. In this research, smartphone devices and smartphone data collection applications were tested and compared to a conventional survey-grade field data collection system to compare the capabilities and possible use cases of each. The test consisted of an evaluation of the accuracy and precision of several mobile devices, followed by a usability analysis of several contemporary data collection applications for the Android operating system. The results of the experiment showed that mobile devices and applications are still less powerful than dedicated conventional data collection systems. However, the performance gap is shrinking over time. The use cases for mobile devices as data collection systems are currently limited to general use and small to mid-size projects, but future development promises expanding capability

Development of a Standalone Pedestrian Navigation System Utilizing Sensor Fusion Strategies

Pedestrian inertial navigation systems yield the foundational information required for many possible indoor navigation and positioning services and applications, but current systems have difficulty providing accurate locational information due to system instability. Through the implementation of a low-cost ultrasonic ranging device added to a foot-mounted inertial navigation system, the ability to detect surrounding obstacles, such as walls, is granted. Using these detected walls as a basis of correction, an intuitive algorithm that can be added to already established systems was developed that allows for the demonstrable reduction of final location errors. After a 160 m walk, final location errors were reduced from 8.9 m to 0.53 m, a reduction of 5.5% of the total distance walked. Furthermore, during a 400 m walk the peak error was reduced from 10.3 m to 1.43 m. With long term system accuracy and stability being largely dependent on the ability of gyroscopes to accurately estimate changes in yaw angle, the purposed system helps correct these inaccuracies, providing strong plausible implementation in obstacle rich environments such as those found indoors

Accuracy Assessment of Perimeter and Area Calculations Using Consumer-Grade GPS Units in Southern Forests

Field foresters have long required a method of accurate measurement of perimeter and area during forest management activities. Perimeter and area assessments that can be derived from individual waypoints collected via global positioning system (GPS) units can be an expensive endeavor. A question of concern for practicing foresters is as the cost of GPS units increase does the accuracy of waypoints and any derived perimeter and area assessments also increase? This research evaluated whether the dynamic collection of waypoints using consumer-grade GPS units ranging from $50 to$700 provide a sufficient level of accuracy for the calculation of perimeter and area under three types of canopy cover: a newly established 3-year-old pine plantation, a 13-year-old pine plantation nearing first thinning, and a 40-year-old mixed pine/hardwood stand. Perimeter and area accuracy was not related to cost indicating that inexpensive GPS units provide an accurate waypoint location when used to derive perimeter and area measurements. When compared to a professional survey of each cover type, the average perimeter root mean square error (RMSE) ranged from 18.72 ft (0.41% of total perimeter) in the 40-year-old mixed pine/hardwood stand to 108.50 ft (2.43% of total perimeter) in the 13-year-old pine plantation. The average area RMSE observed ranged from 0.07 acres (0.22% of total acreage) in the 3-year-old plantation to 1.32 acres (4.67% of total acreage) in the 13-year-old pine plantation. For many forestry applications needing a perimeter and acreage assessment, these levels of accuracy should be more than sufficient

Autonomous Inspection of Electrical Transmission Structures with Airborne UV Sensors and Automated Air Traffic Management

This report details test and measurement flights to demonstrate autonomous UAV (Unmanned Aerial Vehicle) inspection of high-voltage electrical transmission structures. A UAV built with commercial, off-the-shelf hardware and software, supplemented with custom sensors and logging software, measured ultraviolet (UV) emissions from a test generator placed on a low-altitude substation and a medium-altitude switching tower. Since corona discharge precedes catastrophic electrical faults on high-voltage structures, detection and geolocation of ultraviolet emissions is needed to develop a UAV-based self-diagnosing power grid. Signal readings from an onboard ultraviolet sensor were validated during flight with a commercial corona camera. Geolocation was accomplished with onboard GPS; the UAV position was logged to a local ground station and transmitted in real time to a NASA server for tracking in the national airspace. The method has practicality and relevance but not adequacy; either improved UAV position determination technology or increased sensor range is needed to enable broad deployment of this method