Table 1 Formulas and introductions for visual perceptions.

From: Impact of built environment on commuting carbon emissions using big data: a case study of Jinan’s main urban area

Indicators

Formula

Introduction

Openness

Openness = PS

Openness is defined as the proportional contribution of sky elements within the scene, whereas Pixel Sky (PS) quantifies the percentage of sky pixels in image data

Greenness

Greenness = PV

Greenness is defined as the vegetation coverage within the visual field, serving as a metric to quantify the urban street greening level through land cover composition analysis. PV represents the proportion of vegetation pixels

Traffic sign

Traffic sign = PTS

Traffic signs refer to the facilities used to manage traffic, ensure road safety and assist vehicles to pass smoothly. PTS represents the proportion of traffic sign pixels

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