Data-format-description.md

@@ -2,7 +2,14 @@ LightningCast output is produced for several satellites (e.g., GOES-16, GOES-18)
 
 # netCDF4
 
-LightningCast data are re-projected to a [Plate carrée](https://pro.arcgis.com/en/pro-app/latest/help/mapping/properties/plate-carree.htm) projection in order to conform to a requirement in the AWIPS resource that LightningCast utilizes for NOAA's NWS. 
+LightningCast data are re-projected from the native geostationary projection to a [Plate carrée](https://pro.arcgis.com/en/pro-app/latest/help/mapping/properties/plate-carree.htm) projection in order to conform to a requirement in the AWIPS resource that LightningCast utilizes for NOAA's NWS. 
+
+Here is an example file:
+`LightningCast_GOES-16_RadC_20230901-174617.nc`
+
+- `GOES-16` is the satellite
+- `RadC` is the sector (`RadC` is for the CONUS sector; `RadM1` and `RadM2` are Mesoscale sectors)
+- `20230901-174617` is the start time of the GOES-R satellite scan.
 
 This is what the header looks like in an example netCDF4:
 ```
@@ -39,4 +46,35 @@ variables:
 
 The extent of the covered domain is defined by the dimensions `x` (number of lons) and `y` (number of lats), the global attributes for the northwest corner point `NWlat` and `NWlon`, and the global attributes for spacing between points `dx` and `dy`. 
 
-The two variables are very similar. The only difference is that `PLTG_60min_plax` is parallax-corrected using a constant cloud-height assumption, with the attribute variable `parallax_cloud_height_in_m`. 
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+The two variables are very similar. The only difference is that `PLTG_60min_plax` is parallax-corrected using a constant cloud-height assumption based on the attribute variable `parallax_cloud_height_in_m`. 
+
+# geoJSON
+
+The geoJSON format for LightningCast is quite simple. Here is an example filename:
+
+`PLTGGOESEastRadC_20230901_180117.force.json`
+
+- `PLTG` stands for "probability of lightning".
+- `GOESEast` (or `GOESWest`) is the slot of the observing satellite
+- `RadC` (or `RadM1`, `RadM2`, `RadF`) is the sector name
+- `20230901_180117` is the timestamp
+
+Each file has a few global attributes:
+- `"source": "NOAA ProbSevere"`
+- `"product": "LightningCast - P(LTG) in 60 min"`
+- `"validTime": "20230901_180117 UTC"`
+- `"productionTime": "20230901_180428 UTC"`
+- `"type": "FeatureCollection"`
+
+Each feature in the geoJSON is for a discrete probability level (e.g., 10%, 25%, 50%, 75%) and has a geometry of type `"LineString"` or `"Polygon"`, with `"coordinates"` in lon-lat space. 
+
+For a `"Polygon"` for example:
+`"type": "Polygon", "coordinates": [[[-87.776, 49.188], [-87.799, 49.088], [-87.715, 48.946] ... [-87.776, 49.188]]]`
+
+Finally, there are several `"properties"` for each features:
+- `"OPACITY": "0"`      #opacity to fill the contour level   
+- `"BOPACITY": "100"`   #opacity of the boundary of the LineString or Polygon  
+- `"COLOR": "0 0 255"`  #R-G-B triplet for the fill color of the contour 
+- `"BCOLOR": "0 0 255"` #R-G-B triplet for the boundary color of the contour
+- `"WIDTH": "1"`        #width of the contour
+- `"INFO": "PLTG: 10%"` #extra information. `"PLTG: 10%"` means this is a 10% probability of lightning contour
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