Yes, I work for a firefighter department.
When there is a big fire we use the hydrants with a bigger diameter.
Those are projected (the pointe) on the map in the atachment.
We can use them up to 1200 meters away from the fire, that is the lenght of hoses we can use.
In order to find blindspots I wanted to place a perimeter around those points.
The condition is that this perimeter uses the streets, not a circle around the point like the 'buffer'. This because our hoses don't go over buildings, only around them on the street.
You can see a map with only the hydrants and a map with the buffers on the hydrants.