A Novel Index to Detect Vegetation in Urban Areas Using UAV-Based Multispectral Images

Geunsang Lee,Sangho Cho,Jeewook Hwang

doi:10.3390/app11083472

Abstract

Unmanned aerial vehicles (UAVs) equipped with high-resolution multispectral cameras have increasingly been used in urban planning, landscape management, and environmental monitoring as an important complement to traditional satellite remote sensing systems. Interest in urban regeneration projects is on the rise in Korea, and the results of UAV-based urban vegetation analysis are in the spotlight as important data to effectively promote urban regeneration projects. Vegetation indices have been used to obtain vegetation information in a wide area using the multispectral bands of satellites. UAV images have recently been used to obtain vegetation information in a more rapid and precise manner. In this study, multispectral images were acquired using a UAV equipped with a Micasense RedEde MX camera to analyze vegetation indices, such as the Normalized Difference Vegetation Index (NDVI), Green Normalized Difference Vegetation Index (GNDVI), Blue Normalized Difference Vegetation Index (BNDVI), Red Green Blue Vegetation Index (RGBVI), Green Red Vegetation Index (GRVI), and Soil Adjusted Vegetation Index (SAVI). However, in the process of analyzing urban vegetation using the existing vegetation indices, it became clear that the vegetation index values of long-run steel roofing, waterproof coated roofs, and urethane-coated areas are often similar to, or slightly higher than, those of grass. In order to improve the problem of misclassification of vegetation, various equations were tested by combining multispectral bands. Kappa coefficient analysis showed that the squared Red-Blue NDVI index produced the best results when analyzing vegetation reflecting urban land cover. The novel vegetation index developed in this study will be very useful for effective analysis of vegetation in urban areas with various types of land cover, such as long-run steel roofing, waterproof coated roofs, and urethane-coated areas.

Highlights

Extreme heat events have been increasing in frequency and severity, resulting in negative impacts on human health [1,2,3]
The “Urban Heat Islands” (UHIs) effect results in urban areas being hotter than nearby rural areas due to impervious surface cover, decreased cooling due to deforestation, anthropogenic heat release, and high concentrations of air pollutants, which can greatly impair air quality [4,5]
In order to create a pleasant residential environment, it is necessary to develop policies to accurately identify the distribution of vegetation in urban areas and to effectively manage and maintain this vegetation

Summary

Introduction

Extreme heat events have been increasing in frequency and severity, resulting in negative impacts on human health [1,2,3]. Various vegetation indices are used to classify vegetation area from satellite or Unmanned Aerial Vehicle (UAV) images. This study aimed to develop a novel vegetation index that accurately reflects the characteristics of urban land cover, such as long-run steel roofing, waterproof coated roofs, and urethanecoated areas, using UAV-based multispectral images. By combining the images for each band using ArcGIS S/W, various vegetation indices, such as the NDVI, GNDVI, BNDVI, RGBVI, GRVI, and SAVI, were calculated. A novel vegetation index was derived to effectively analyze the vegetation distribution area reflecting the urban land cover

Study Area

Findings

A Novel Vegetation Index That Accurately Reflects Urban Land Cover