The pixel (the width of a single pixel on the map graphic on the Location page) is used as the standard distance unit of the wiki because it is used in the base coding of Cantr. Vehicle speeds are measured in pixels per day.
The map graphic is a circle of unknown radius. If you click it, you see the old overview, which is a 35 pixels square, centered on the character's current location; therefore the map covers a visible radius of 17.5 pixels to 24.75 pixels, depending on the direction.
Characters can see (and therefore point at, talk to and attack) characters 5 pixels in either direction on a road.