VIIRS

-----------
Last updated on 6/30/2015 11:48:26 AM.

VIIRS Overview

This data layer displays VIIRS (Visible/Infrared Imager/Radiometer Suite) satellite I-band fire detection data. VIIRS is based on a sensor that builds on the heritage of MODIS, with a markedly smaller pixel 'footprint' (375 meters for VIIRS, 1km for MODIS).

VIIRS data comes into WFDSS less frequently than MODIS, and its hosting satellite (Suomi NPP) generally passes once, sometimes twice, in a 24 hour period. Lapses in data lead users to think it is broken when it is likely just below the horizon for an extended period. VIIRS data can be delayed an hour or two between showing up on Active Fire Maps and showing up in WFDSS.

While both sensors produce data of similar accuracy in relative terms, because of the smaller pixel size, relative positioning errors from VIIRS appear to be smaller in real terms. VIIRS is not processed to the same degree as MODIS, and while VIIRS may appear to have higher sensitivity, the higher sensitivity appears to be correlated with a higher number of "false-positive" detections. Be aware that sensitivity, defined as "the amount of heat required to trigger a change in state for a pixel from 'off' to 'on', is specified in an algorithm and will change as the VIIRS detection algorithms are refined.

VIIRS fire detection data are suitable for evaluating fire activity and general direction of spread. As with MODIS, these data are subject to substantial positional shift and should not be used as a replacement for more accurate fire mapping sources when available.

VIIRS Data Input

This data layer is accessed via an external Web Mapping Service (WMS). The data request is channeled through the WFDSS WMS servlet for projection issues related to switching map base layers.

VIIRS 6 Hr

This data layer displays the VIIRS thermal detections for fire activity in the area you select for the six hours preceding the current date and time displayed on the VIIRS page. See https://fsapps.nwcg.gov/afm/gisdata.php.

VIIRS 12 Hr

This data layer displays the VIIRS thermal detections for fire activity in the area you select for the 12 hours preceding the current date and time displayed on the VIIRS page. See https://fsapps.nwcg.gov/afm/gisdata.php.

VIIRS 24 Hr

This data layer displays the VIIRS thermal detections for fire activity in the area you select for the 24 hours preceding the current date and time displayed on the VIIRS page. See https://fsapps.nwcg.gov/afm/gisdata.php.

VIIRS YTD

This data layer displays the VIIRS thermal detections for cumulative fire activity detected since the beginning of the calendar year. See https://fsapps.nwcg.gov/afm/gisdata.php.