Urban Green Spaces
This term refers to areas in cities that have trees, grass, or other vegetation.
What is a green space?
The total amount of green space gained in central Beijing between 2016 and 2020
What is 48.62 square kilometers?
The purpose of filtering satellite images before analysis is to improve this aspect of the data.
What is accuracy?
This free cloud based platform was used to process all satellite imagery in the study
What is Google Earth Engine?
The study area covered this many districts in central Beijing
What is six?
The simple vegetation index that the paper argues is insufficient on its own for measuring green space quality
What is NDVI?
This was the only district in the study area to lose green space between 2016 and 2020
What is Haidian District?
To remove clouds from satellite images, the researchers used this specific quality band in the data.
What is QA60?
This type of satellite provided the primary imagery used in the study at 10 meter resolution
What is Sentinel-2?
The average overall accuracy achieved by the mapping workflow across all five years
What is 96.47%?
The number of landscape pattern indicators used to assess green space quality and distribution in this study
What is six?
Rather than improving steadily, green space quality did this in 2018 before declining slightly through 2019 and 2020
What is peaked?
The researchers only used satellite images that had less than this percent of cloud cover.
What is 7%?
Rather than collecting new field data every year, the researchers used this technique to update their maps annually
What is training sample migration?
This classifier outperformed SVM and CART not necessarily in peak accuracy but in stability across varying training sample sizes
What is Random Forest?
This index measures the proportion of vegetation coverage within a 300 meter radius of any given point in the city
What is the Urban Green Index (UGI)?
Despite gains in green space area and coverage quality, this aspect of urban vegetation showed almost no improvement across the five year study period
What is vegetation diversity?
Images were filtered to this specific season to capture peak vegetation growth in the study area
What is summer (June 21 to September 21)?
To classify vegetation automatically, the researchers first applied this method to separate vegetation from non-vegetation.
What is Otsu’s method?
This was the weakest performing vegetation class across all classifiers, with a producer accuracy of only 71% using Random Forest
What is low plants (grassland)?
This index measures the variety of different vegetation types within a 300 meter radius of any given point, and showed little improvement over the study period
What is Shannon's Diversity Index (SHDI)?
The two districts that drove the majority of green space gains in central Beijing between 2016 and 2020
What are Chaoyang and Fengtai?
This is the term used in the paper to describe the process of calculating a single representative pixel value from an entire collection of summer satellite images
What is image reduction?
To avoid collecting new training data each year, the researchers reused samples from this year as the baseline for later years.
What is 2016?
This was the year that produced the highest overall mapping accuracy of the entire study period at 98.47%
What is 2019?