About NTL Explorer

NTL Explorer is an analytical workspace for examining how nighttime light changes over time—across Indian districts, countries, European regions, or a custom point and area anywhere on Earth.

What you can do

• Open a precomputed region for a fast monthly radiance history.
• Compare raw VIIRS observations with the PSTT2021 cloud-bias correction where it is available.
• View district economic series beside indexed nighttime lights without implying that the two are the same measure.
• Draw an area or enter coordinates for an on-demand Google Earth Engine query.
• Pin regions for comparison, compare two years side by side, and export charts and data (CSV, PNG, SVG, GeoJSON, GIF timelapse).

Coverage and freshness

Indian district boundaries use the Census of India 2011 geography. That choice provides a reproducible historical unit, but it does not represent every later district split or state reorganisation. The selected panel states the last available NTL month and the exact GDP definition, base year, and fiscal-year coverage.

Methodology

The interface combines precomputed regional panels with live Earth Engine queries. Every chart distinguishes the observation source and transformation used.

Nighttime lights

The core series uses the monthly stray-light-corrected VIIRS DNB composite NOAA/VIIRS/DNB/MONTHLY_V1/VCMSLCFG. Regional values are mean radiance in nW/cm²/sr. Annual values shown by the interface are calendar-year means with at least six available monthly observations.

For covered Indian districts, “Corrected” refers to the PSTT2021 cloud-bias correction. “Raw” is the source composite. A custom point or polygon is computed live and is raw only.

Growth calculations

Cumulative growth compares the first and last available annual windows. CAGR uses the calendar-year span between those windows. The ranking table excludes extremely low baseline radiance because percentage changes from values near zero are unstable.

District economy

District domestic product is compiled from State DES and MoSPI-linked sources, with Dataful-supplied state files used where present. A district series is selected as one consistent combination of measure (GDDP or NDDP), price basis (constant or current), and—where the source publishes it—base year. A missing constant-price base year is explicitly flagged. Fiscal years are keyed by their starting year; for example, 2023 means FY 2023–24.

Priority is GDDP at constant prices, then NDDP at constant prices, then GDDP and NDDP at current prices. Quarter-only observations are excluded. Large year-to-year changes are retained and flagged rather than silently removed.

Boundaries and joins

India uses Census 2011 district boundaries. Data joins require both state and district identity; ambiguous state-less names are rejected. Stable IDs are derived from state code and district name so regenerating a boundary file does not change identity merely because feature order changed.

Live-query safeguards

The backend validates coordinate bounds, real date ranges, vertex counts, polygon self-intersection, and area before submitting work to Earth Engine. Custom areas are capped at 250,000 km² and requests time out after 25 seconds.