Pokemon-go – What do these empty white ripples on the map mean

Note: As of Pokemon GO version 0.29.1 or so, the "footprint" indicator was disabled, and all Pokemon are three footprints away. This is a known bug, and the fault of Niantic Labs (and the server overload as a result of the game's popularity.

Note 2: As of Pokemon GO Version 0.30.1, the Footstep indicators have been removed. The game will show all Pokemon within 200 meters of your current location, with the nearest being anywhere in the list.

These steps represent the distance from the Pokemon currently.

Each footprint represents 50 meters of distance, starting with zero footprints means the Pokemon is no more than 50 meters away.

For example, one footprint means the Pokemon can be 51-100 meters away in any direction. Three footprints means the Pokemon is at most 200 meters away.

Note, however, that these numbers do not reflect Pokemon spawned through Incense or Lure Modules. Additionally, there is (at the time of writing - version 0.29.0) a bug that causes the distances to not update properly, causing the approximate values to be slightly "off."

We can determine the 'scale' by observing the 'proximity circle' that emits from the player. At its brightest, before it starts to fades, it has a radius of exactly 40m real-world.

As determined through a different question, the circle that emits from the centre of your character has a total radius of 40 metres at its largest size. You can use this to gauge approximate distances, in proximity.

I have also used comparison to Google Maps, which has a distance measuring mechanic, to further approximate the viewing distances. I took measurements at two different angles. The zoomed out position, looking down on the player so I had as much visible in the background as possible, and zoomed in, looking straight ahead.

When zoomed out and looking down, you can see ahead by approximately 500 metres. You should still see roughly 50 metres behind you.

When zoomed in and looking forward, you can see ahead by approximately 700 metres. You should still see roughly 30 metres behind you.

I found comparing distances using Google Maps to be the most effective, as Google Maps appears to be 100% accurate in terms of layout, right down to the exact shape, position, and size of each house. This lets you triangulate exact positions and distances using the corners of the actual house images.