When Lightning Strikes

California has already had another bad fire year with many hundreds of fires burning throughout the state, most started by lightning. Between June 21 and June 22 there were nearly 10,000 strikes (9,927 to be exact). Here’s an Explorer view of the strikes during that period.

So how did we do this? Let’s take a closer look…

How was the lightning strike information captured? Vaisala is company specializing in a variety of real-time detection systems and services, and has established the National Lightning Detection Network (NLDN). This nationwide sensor-based detection system tracks cloud-to-ground lightning activity across the continental US, 24 hours a day, 365 days a year. While the Bureau of Land Management once had their own detection grid, the BLM now contracts out to Vaisala, using their detection grid.

The Automated Lightning Mapping System (ALMS) extension for ArcGIS was used to download the near real time strike location information from the BLM data server. Using the extension strike information can be chosen for a particular time frame and geographic extent. The data was download via the internet in shapefile format.

In Explorer we chose File > Open > Shapefiles to add the shapefile data to our map. We wanted to symbolize the lightning strikes using our own lightning symbol. We made one using Photoshop, starting by creating a new image with square dimensions (we chose 30 pixels a side) and making sure our background was transparent. We drew our lightning bolt, then saved it as a local PNG file.

The next step was to use our new symbol for the lightning strikes. Here we’ve opened the Select Symbol window.

But rather than choosing one of the existing symbols, we clicked Add a Symbol and navigated to the folder that we saved our PNG from above in, and selected our custom symbol instead.

The ESRI Wildfire Management site has more information on using GIS for wildfire management, prevention, and suppression. Also see the Adding a new symbol Explorer Help topic.

(Thanks to Tom Patterson, ESRI Wildland Fire Specialist, for providing information and data)


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