DMSP and MODIS

DMSP boat lights and MODIS sst and Chlor-a

Feb 2002

Boats lights from the DMSP global image from Chris Eldridge compared with MODIS sst and Chlorophyll-a for an area of the Argentina coast where the Malvinas and Brazil currents meet.

This image shows the chlorophyll-a product from MODOCL2A from September 9, 2001. The chlorophyll-a had many negative values, (which Jim Acker explained where a known algorithm problem for that particular area off the coast of Argentina) so the applied colortable is arbitrary. The white areas are DMSP boats lights from 1994-5?

This image shows the sst product from MOD28L2 from September 9, 2001. This is a daytime sst scene. The white areas are DMSP boats lights from 1994-5?

here is the readme for the DMSP data

May 22, 1998
World Stable Lights Images - October 1994 to March 1995
Derived from DMSP OLS Nighttime Imagery during the dark half of each lunar cycle.
- 30 Arc Second Grid & 1 km Goode Projection

The image files on this tape represent the first preliminary version of the global stable lights produced at NOAA/NGDC. These images may vary slightly from previous versions due to an updated geolocation algorithm and a modified cloud thresholding technique. Improvements are currently being made on the reprojection algorithm which will in turn cause the image values to change slightly, but that final version will be the most accurate and will replace the images provided on this tape.

The 6 months of OLS data were compiled into one global image of lights where each pixel's value represents the frequency of occurrence of a light in cloud-free imagery for that pixel. This global image was then thresholded at 6% to remove most of the noise and ephemeral light sources. Some areas of the world had a lot of burning during these 6 months which could not be thresholded out without compromising many of the smaller towns. These areas were manually "cut" from the final image. The same procedure was done for heavily fished areas where lights from the boats are picked up in the DMSP-OLS imagery. Finally, for interest an attempt at picking out a lot of the world's gas flares was done. This was done manually, and it is certain that we did not get all of the flares identified. These remaining flares will still be present in the cities image.

This manual cropping procedure resulted in 4 different image "layers" - named for each of the type of light represented: city lights, gas flares, boats, and fires.

If you have any questions regarding the data or the file formats,
please contact:
Dr. Chris Elvidge
Solar-Terrestrial Physics Division
NOAA National Geophysical Data Center
3100 Marine Street RL-3 Room 121
Boulder, CO 80303
Tel: 303-497-6121 Fax: 303-497-6513
email: celvidge@ngdc.noaa.gov

or: Kimberly Baugh
Solar-Terrestrial Physics Division
NOAA National Geophysical Data Center
3100 Marine Street RL-3 Room 103
Boulder, CO 80303
Tel: 303-497-6945 Fax: 303-497-6513
email: kbaugh@ngdc.noaa.gov020404 15:07 [0] >