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Accurate and consistent information on forest area and forest area change is essential to the reporting requirements for countries to access results-based payments for REDD+.

To support assessing the uncertainties of these maps in terms of accuracy and precision, FAO has produced a new resource publication Map Accuracy Assessment and Area Estimation: A Practical Guide. It builds upon the publication Good practices for estimating area and assessing accuracy of land change by Pontus Olofsson and other authors, using it as a framework to provide recommendations for designing and implementing an accuracy assessment for land cover and land cover change maps.

This uncertainty can be assessed by comparing the mapped land classification to higher quality reference data, collected through a sample-based approach. The ultimate goal of that process is to correct the area estimates for map bias, by producing adjusted area estimates with confidence intervals.

The resource publication guides the user through the different aspects of an accuracy assessment, including: the theoretical background and recommendations for the setup of the sampling design, reference data collection and the analysis of the results. Following this guidance, a user can quantify map accuracy through the creation of error matrices, produce area and area change estimates that are adjusted for the map bias, and quantify the precision of the area and area change estimates through the calculation of confidence intervals.

The theoretical background and recommendations presented in this publication are accompanied by a step-by-step guide of practical implementation, using open source software. It includes suggestions for cost-effective collection of reference data, using Open Foris Collect Earth that facilitates sample-based assessments and collection of reference data from medium, high and very high spatial resolution satellite imagery in conjunction with Google Earth, Bing Maps, Here Maps and Google Earth Engine API.

Download the publication in English here (coming soon).

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