Click on the map that Wrightwood posted and read the legend, etc. All the info is there.
map:
https://bit.ly/3cjcYnoLegend Info
The fire maps I produce can display three kinds of information.
1. Satellite hotspots
Red triangle = MODIS satellite hotspot
Orange square = VIIRS satellite hotspot
All MODIS and VIIRS satellite hotspots on the map were detected within the last 24 hours. There are a total of 6 to 8 satellite passes per 24 hours. After a satellite pass it takes about 3 hours for NASA to process the data and up to another hour before that data appears on NASA's FTP download site. As a result, when you see satellite hotspot data on a map that data is already at least 3 to 4 hours old!
Satellite hotspot locations are approximate. A MODIS hotspot represents a box 1,000 meters (~0.62 miles) by 1,000 meters. The actual detection could be anywhere inside that box. A VIIRS hotspot represents a box 375 meters (~0.23 miles) by 375 meters.
A satellite hotspot can be a 'false positive' when (1) the fire is near the edge of the 'strip' of land that the satellite sees and (2) there is heavy smoke with hot embers. Likewise, an area can burn and never show up on the map as a hotspot. This can happen when a grassy area burns just after a satellite pass and then cools before the next satellite pass.
2. Fire perimeter and related data
If the map shows a fire perimeter, then here is the legend for that data. Currently you cannot turn this data off. That feature will be added in the future.
Red and black line = Fire perimeter
White line = Estimated perimeter
Red shaded = Intense fire
Yellow shaded = Scattered fire
Red dot = Isolated fire
Blue box = No infrared data
Grayed out areas = Heavy clouds affected infrared data
Fire perimeters are typically produced at night by fire staff who analyze infrared data from a nighttime overflight. The perimeter data is then used on a wide variety of maps for the coming day. The infrared analyst also identifies areas of intense, scattered and isolated heat.
2. Date layers hosted on GIS servers
Most GIS overlay layers that this map can display only have a single type of symbol. To see what symbol is used for a layer you can turn the layer on/off a couple of times. The symbol used for that layer should be obvious. Note that some overlay layers might be defined on the GIS server so that they only display at certain zoom levels. You might need to zoom in or out for the data to display. And if the GIS server hosting the data is busy it might take more than a few seconds for the data to appear on the map.
A few GIS overlay layers have multiple symbols or colored areas that mean different things. Those layers are listed below along with a link to the legend graphic which is hosted on the GIS server. Look at the layer number in the list below and then find that same layer number in the legend graphic.
