Most modern interactive maps are made up of many small, square images called tiles. These tiles are typically 256×256 pixels and are placed side-by-side in order to create the illusion of a very large seamless image. As you zoom and pan to navigate around the map, the mapping engine fetches the tiles required to display the map at your current area. This tiling of the map allows you to efficiently view a small part of the planet without having to load massive resources.
There are several different map tiling schemes, but the most popular is the standard XYZ tile scheme, used by Google, OpenStreetMap, CARTO, Mapbox, and others. This system implements a numbering scheme where Z is the zoom level, and X and Y identify the tile location.
Traditional maps require a projection to represent the three dimensional globe on a two dimensional surface. Every projection introduces some type of distortion and when Google was developing their system of tiled images, they selected a Spherical Mercator projection which preserves shape and angles but exaggerates areas near the poles. Most global mapping services provide their tiles in Spherical Mercator (also known as Web Mercator).
Custom Map Layers
Fulcrum supports custom maps layers in the Web Mercator projection with the XYZ tile scheme. These maps can come from an online service provider (Mapbox, OpenStreetMap, etc.) via a REST API or a tileset database that follows the raster MBTiles specification.
There are many web mapping services that make their content available for consumption in other applications, such as Fulcrum. Many commercial mapping services offer paid subscriptions for access to their content and may also include restrictions regarding access and usage outside their platform.
Commercial Service Providers
Many services leverage mapping data from OpenStreetMap (OSM), a community-driven mapping platform. While OSM does make their map tiles available for general use, their tile usage policy includes restrictions to prevent overwhelming their servers. Since OSM data is freely licensed, many commercial map providers utilize this data in their own services, which are generally available via subscription. Popular OSM-based map services include:
Other companies manage their own data and may offer additional layers such as satellite imagery, navigation charts, and demographic overlays.
Government Mapping Services
In addition to commercial services, many governments and other large organizations that maintain geospatial data have their own map servers for providing content to the public via their APIs.
Serving Your Own Data
If you’ve got your own geospatial data that you want to serve up to consume in Fulcrum or other applications, you can either leverage a platform such as Mapbox, CARTO, etc. or stand up your own map server. OpenMapTiles Server is great for serving up OSM vector tiles and GeoServer and Mapserver can be configured with caching to serve rendered map tiles.
Adding a Map Layer to Fulcrum
Now that you have learned more about map layers, it is time to go and add your own to your Fulcrum account. Please check out the following tutorial: