Map Tiles

Map tiles is a complicated concept that is used to be able to load a drawn basemap or imagery at any zoom quickly.

Basically there are up to 24 levels of tiles for any map. Tile size 1 shows the whole world, tile size 2 shows 1/4 of the world, size 3 shows 1/16, size 4 1/64... on and on exponentially.

Tile size (or zoom level) 10 fits all of philadelphia into a map. We have Atlas set up to load on zoom level 12, so you can see Center City and the surrounding neighborhoods on load.

After you search an address it centers on the address and zooms into 17. At that zoom it would take 4 to the 17th power (17,179,869,184 or +17 billion) tiles to cover the earth. Fortunately, when you make the map tiles for Philadelphia, it only makes the ones necessary to fill out the city. But at zoom level 24, you're zoomed into closer than room level, and it still takes millions of tiles to cover all of Philadelphia. Creating a set of tiles is a process that you have to let run for a little while. I think all Tile Layers in the City of Philadelphia are only tiled up to zoom 22. We set Atlas to max out at zoom 22 and not allow zooming in closer.

When you go to a rest service for a set of tiles like https://tiles.arcgis.com/tiles/fLeGjb7u4uXqeF9q/arcgis/rest/services/CityImagery_2023/MapServer you can see that it tells you all of the zoom levels that have been tiled:

In the 2 screenshots below, you can see that as the map was zoomed in past the next zoom level, the map component made network calls to get different, more zoomed in tiles of the exact same area it had already gotten tiles for: