Abstract
Thematic mapping provides today’s analysts with an essential geospatial science tool for conveying spatial information. The advancement of remote sensing and computer science technologies has provided classification methods for mapping at both pixel-based and object-based analysis, for increasingly complex environments. These thematic maps then serve as vital resources for a variety of research and management needs. However, to properly use the resulting thematic map as a decision-making support tool, an assessment of map accuracy must be performed. The methods for assessing thematic accuracy have coalesced into a site-specific multivariate analysis of error, measuring uncertainty in relation to an established reality known as reference data. Ensuring statistical validity, access and time constraints, and immense costs limit the collection of reference data in many projects. Therefore, this research proposes evaluating the feasibility of adopting the low-cost, flexible, high-resolution sensor-capable Unmanned Aerial Systems (UAS, UAV, or Drone) platform for collecting reference data to use in thematic map accuracy assessments for complex environments. This pilot study analyzed 377.57 ha of New England forests, over six University of New Hampshire woodland properties, to compare the similarity between UAS-derived orthomosaic samples and ground-based continuous forest inventory (CFI) plot classifications of deciduous, mixed, and coniferous forest cover types. Using an eBee Plus fixed-wing UAS, 9173 images were acquired and used to create six comprehensive orthomosaics. Agreement between our UAS orthomosaics and ground-based sampling forest compositions reached 71.43% for pixel-based classification and 85.71% for object-based classification reference data methods. Despite several documented sources of uncertainty or error, this research demonstrated that UAS are capable of highly efficient and effective thematic map accuracy assessment reference data collection. As UAS hardware, software, and implementation policies continue to evolve, the potential to meet the challenges of accurate and timely reference data collection will only increase.
Highlights
Growing dissidence over the causes and impacts of environmental change in the modern era has forced an ever-increasing need for data accuracy and certainty
To properly apply the practice of using high-resolution remote sensing imagery as a source of validation data [36,47,48], our research focuses on if Unmanned Aerial Systems (UAS) provide the potential for collecting thematic map accuracy assessment reference data of a necessary quality and operational efficiency to endorse their use
We evaluated the agreement between the UAS-collected samples and the ground-based continuous forest inventory (CFI) plot
Summary
Growing dissidence over the causes and impacts of environmental change in the modern era has forced an ever-increasing need for data accuracy and certainty. Studied patterns of global change such as habitat augmentation, loss of biodiversity, invasive species spread, and other systems imbalances have designated humans as a ubiquitous disturbance for the natural world, leading to the current ‘Anthropocene’ era [1,2,3]. Forests 2019, 10, 24 and quality of life through diminished potential for ecosystem services [4]. These services include life sustaining functions such as nutrient regulation, primary production products in agriculture and forestry, water quality management, and disease mitigation [1,2,5]. We can employ remote sensing as a tool to collect land cover data at scales sufficient to overcome environmental issues [8,9,10]
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