基于GEE平台的广州市主城区不透水面时间序列提取

不透水面作为城市化水平以及城市环境的重要评价指标,其提取已经是当下的研究热点。与单时相影像相比,时间序列制图能够获取其准确的变化趋势,对于监测城市的快速发展具有重要意义。本文以广州市主城区为研究区,以Google Earth Engine平台为基础,利用2000-2017年的Landsat TOA影像计算BCI和NDVI,并通过自适应迭代法确定它们的阈值,从而提取初始的不透水面,然后进行时间一致性检验,使不透水面时间序列更加合理。研究结果表明:①BCI与NDVI的结合以及时间一致性检验能够提高不透水面的提取质量;②本文中不透水面提取的平均总体精度为90.4%,平均Kappa系数为0.812;③在2000-2017年广州市主城区不透水面面积增加近一倍,但增速有所放缓。④新增的不透水面主要集中在原本相对落后的主城区外围;⑤高程、道路密度和购物场所密度等是影响广州市主城区不透水面扩张的主要因素。

Mapping Impervious Surface Dynamics of Guangzhou Downtown based on Google Earth Engine

For assessing urbanization level and urban environment, the mapping of impervious surface has become a research hotspot. Compared with single-phase imagery, time series mapping can depict temporal trends, which is of great significance for monitoring urban expansion. Based on the Google Earth Engine platform, this paper calculated BCI and NDVI using Landsat TOA data from 2000 to 2017, and determined their thresholds by an adaptive iteration method to extract the initial impervious surface. Then, Temporal Consistency Check (TCC) was performed to make the time series of impervious surface more reasonable. Results show that: (1) Adding NDVI to both BCI and TCC improved the quality of impervious surface mapping. (2) The average accuracy of impervious surface mapping in this paper was 90.4%, and the average Kappa coefficient was 0.812. (3) The impervious surface area of Guangzhou downtown nearly doubled from 2000 to 2017 with a decreasing growth rate. (4)The newly developed impervious surface mainly concentrated on the relatively backward outskirts of Guangzhou downtown. (5) Elevation, road density, and shopping mart density were the main factors influencing the expansion of impervious surface.