Visible Built-up Index — See the city in visible light.
REMOTE SENSING LETTERS · 2026
A built-up index designed to reveal bright urban surfaces using only red, green, and blue satellite bands—at 10-metre resolution.
Traditional built-up indices often rely on shortwave infrared bands. VBI asks a simpler question:
Can the brightness and color purity of a surface reveal the built environment?
01 · METHOD
RGB becomes a built-up signal.
Sentinel-2 red, green, and blue reflectance are transformed into HSV Value and Saturation. VBI normalizes their contrast into a single index from −1 to +1.
Sentinel-2 RGB→HSV transform→VBI
VBI =Value − SaturationValue + Saturation
Value = max(red, green, blue)Saturation = (Value − min RGB) / Value
INTERACTIVE FORMULA LAB
Change the visible reflectance.
Bright, low-saturation surfaces tend toward higher VBI values. Move the channels to see how the relationship changes.
Simulated surface
Value0.720
Saturation0.194
VBI0.575
Mapped built-upCórdoba threshold: VBI ≥ −0.373
02 · EVIDENCE
Tested against built-up standards.
The study compared VBI with 11 spectral indices using 615 visually interpreted pixels from Córdoba, Argentina. The main paper reports VBI, BU, and NDBI in detail.
DIAGNOSTIC ABILITY
n = 615 reference pixelsArea under the TOC curve
Higher AUC indicates stronger discrimination across all possible thresholds. These values describe the Córdoba validation dataset.
178 of 205 built-up samples detected
86.83%154 of 205 built-up samples detected
75.12%128 of 205 built-up samples detected
62.44%03 · CÓRDOBA MAP ATLAS
From satellite scene to classification.
Move through the original study landscape, continuous index values, and final threshold maps.
Li et al. (2026)SENTINEL-2 · 24 JANUARY 2024
The Córdoba study landscape
The 601 km² study area combines a dense reflective urban core, suburban vegetation, the Suquía River, cropland, and fallow fields. The points show the 615 pixels used for validation.
Non-built-upBuilt-up
04 · READ BEFORE USE
A focused index, not a universal classifier.
Validate locally
The published thresholds were calibrated in Córdoba and should not be treated as globally optimal.
Watch bright soils
Dry, reflective bare soil can produce a built-up-like signal and remains an important confusion class.
Expect dark omissions
Terracotta roofs, asphalt roads, shadows, and vegetation-covered structures may be overlooked.
PUBLICATION
The visible built-up index: advancing the detection of high-albedo urban areas
Weizhi Li, Aiyin Zhang & Florencia Sangermano · Remote Sensing Letters, 17(2), 123–131 (2026)