Abstract
GlobeLand30, the world’s first 30m-resolution global land cover data set, has recently been issued for research on global change at a fine resolution. Given the accuracy of GlobeLand30 data may show significant variation in different parts of the world and data quality at continental scale has not been validated yet, this study aims to evaluate the uncertainty of the data over Central Asia. Since it is difficult to get long-term historical ground references, GlobeLand30 data at the most recent epoch (<i>i.e.</i>, GlobeLand30-2010) was assessed. In the test, a large sample size was adopted, and more than 25 thousand samples were selected by a random sampling scheme and interpreted manually as ground references based on higher resolution imagery at the same epoch, such as images from ZY-3 (China Resources Series) satellite and Google earth. Cross validation of image interpretation by three well-trained interpreters was adopted to make the references more reliable. Error matrix and <i>Kappa</i> coefficient were utilized to quantify data accuracies in terms of classification accuracy. Results show that the GlobeLand30-2010 data presents an overall accuracy of 46% in the study area. As for specific land cover types, bare land illustrates a high user’s accuracy but a lower producer’s accuracy. At the same time, the accuracies of grassland and forest are significantly lower than other types. The majority of misclassification types come from bare land. It implies a difficulty of distinguishing grassland or forest from bare land in the study area. In addition, the confusion between shrub land and grassland also results in the misclassification. The results serve as a useful reference of data accuracy for further analysis of land cover change in Central Asia as well as the applications of GlobeLand30 data at a regional or continental scale.
Highlights
Central Asia located in the hinterland of the Eurasian Continent is a typical continental inland arid region
The result indicates an overall accuracy of 46% with Kappa coefficient of 0.283 for the study area
Existing globalscale land cover products have been declared a satisfied classification accuracy, variation may still exist at different areas of the world
Summary
Central Asia located in the hinterland of the Eurasian Continent is a typical continental inland arid region. It has a harsh arid environment and its eco-system is very fragile. Mapping land cover change with remote sensing at a large spatial scale have been studied for the past decades. Due to the limitation of remote sensing technology on the balance between imagery coverage and spatial resolution, most land cover products at the global scale present coarse spatial resolutions, e.g., 300 m or much coarser. The most common products include Global Land Cover Classification (1981-1994) issued by The University of Maryland (UMD) (Hansen et al, 2000), MODIS Land Cover Type Yearly L3 Global 500 m (MCD12Q1) issued by National Arial Space Agency (NASA) of the United States, GLC2000 Global issued by the European Commission's Joint Research Centre (JRC), and GlobCover Land Cover Maps (v2.2, v2.3) issued by European Space Agency (ESA)
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