Nighttime Lights of the World - Change Pair (Version 1)



The DMSP group at NGDC released version one of a pair of DMSP-OLS "nighttime lights of the world" images processed specifically for the detection of change, covering the years 1992-93 and 2000. The images are in ENVI and Geotiff formats.
Our lab began work on methods and algorithms for producing high quality nighttime lights for use in change detection in early 2001. The digital OLS archive extends to mid-1992 but has numerous gaps in the first year. Therefore we combined the 1992 and 1993 data for the early product. The OLS detects lights from human settlements, fires, gas flares, and heavily lit boats (primarily squid fishing boats). We have separated the four types of lights as best we could based on location, brightness / persistence, and visual appearance. In addition to these four global cloud free products we also provide key intermediate products: number of valid coverages, number of cloud free coverages, number of cloud free light detections, and the average DN of the cloud free light detections.
There are still some problems with the data. One problem that cannot be address is the saturation of the visible band in the bright cores of urban centers. This is a characteristics of the operational OLS data, which forms the bulk of the archive. It is difficult using OLS alone to adequately separate gas flares from human settlements. We are investigating the use of persistent MODIS fire detections as a guide for locating gas flares in the OLS data. Likewise, the separation of city lights and fires is not entirely clean in some parts of the world with extensive fires. The other major problem we note in the current product set are the effects of snow on the extent and brightness of the lights, which can be found in the northern hemisphere above ~40 degrees latitude. A good place to look for the effects of snow is in the Great Lakes region of the USA. We plan to reprocess the products in the next several months using an improved cloud detection algorithm and screen for snow using DMSP SSMI data. Preliminary cloud-free snow-free product sets indicate that snow effects will be reduced in the next release.
Our plan is to process the entire digital OLS time series into annual nighttime lights composites and to develop a cross calibration for the four OLS' that have produced nighttime data for the archive to date (on F-10, F-12, F-14, and F-15) using the prelaunch sensor characterizations and empirical results from nights where lights were observed by multiple (2-3) OLS'.
The products released contain a number of interesting phenomena resulting from the expansion (and contraction) or lighting. Below are four color nighttime lights change images produced from the released data.
Nighttime lights change images:
(The year 2000 compared with 1992-93)
Brazil Florida
Italy Ukraine

The above images can be interpreted using the following key:
Cyan background - no lights and offshore (land / sea mask applied).
Black bright lights detected in both time periods (at or near saturation).
Red Lights much brighter in 2000.
Yellow New lights in 2000.
Light gray Dim lighting detected in both time periods - little change in brightness.
Blue Lights dimmer or missing in 2000 (relative to 1992-93).

Download 1992-1993:

Warning: Disk space required for compressed data is ~800 MB and uncompressed data is ~12 GB.
Data set and definitionsD/L EnviD/L TIFData file sizes
Stable LightsENVI TIF Compressed ~13 MB/Uncompressed ~700 MB
Human SettlementsENVITIFCompressed ~12 MB/Uncompressed ~700 MB
Fires  Not available
BoatsENVITIF Compressed ~2 MB/Uncompressed ~700 MB
Gas FlaresENVITIFCompressed ~1.5 MB/Uncompressed ~700 MB
Cloud Free Lights CountENVITIF Compressed ~109 MB/Uncompressed ~1.4 GB
Valid CoveragesENVITIFCompressed ~91 MB/Uncompressed ~1.4 GB
Cloud Free CoveragesENVITIF Compressed ~327 MB/Uncompressed ~1.4 GB
Unfiltered average visible DN of cloud free lightsENVITIF Compressed ~99 MB/Uncompressed ~700 MB

Download 2000:

Warning: Disk space required for compressed data is ~800 MB and uncompressed data is ~12 GB.

Data set and definitionsD/L EnviD/L TIFData file sizes
Stable Lights ENVI TIF Compressed ~14 MB/Uncompressed ~700 MB
Human SettlementsENVITIF Compressed ~13 MB/Uncompressed ~700 MB
FiresENVI TIFCompressed ~8 MB/Uncompressed ~700 MB
BoatsENVI TIF Compressed ~2 MB/Uncompressed ~700 MB
Gas FlaresENVITIFCompressed ~1.5 MB/Uncompressed ~700 MB
Cloud Free Lights CountENVI TIF Compressed ~89 MB/Uncompressed ~1.4 GB
Valid CoveragesENVITIFCompressed ~65 MB/Uncompressed ~1.4 GB
Cloud Free CoveragesENVITIF Compressed ~302 MB/Uncompressed ~1.4 GB
Unfiltered average visible DN of cloud free lightsENVITIF Compressed ~100 MB/Uncompressed ~700 mg
Each tar ball contains the data file, an associated header file, four jpeg images and a readme file. The data files have been zipped with gzip.