1. The technology used to build, compile and serve the maps to the user.
2. The data that makes up the maps.
3. The style of the map, i.e. the look of the map.
All three of these components in my opinion are the key ingredients to an online maps success. I will briefly outline each of these below.
Q) What technology is commonly used to build, compile and serve these maps?
A) Map Server is an example of an open source software which provides a platform to serve out spatial data via the web. http://mapserver.org/. Esri and their suite of software products (ArcMap and ArcGIS Server) is an example of a closed source piece of software and is used by many large government and private sectors to serve maps out via the web. www.esri.com.
The Map Tools website provides some other links to commonly used packages and tools which users can combine to build their maps. http://www.maptools.org/.
Essentially though you need a program that can import spatial data, geoprocess the data and style the data. That will take care of the build and compilation of your map. Then you need to work out how you are going to serve the data to your users. Firstly you need a server. It can be your local machine or you can rent some server space in the 'cloud' or it can be on your network at your workplace. Check out the service Amazon provide http://aws.amazon.com/ for more information regarding cloud servers.
Once you have your server selected then you need a program/application that will take your map and publish it to the server as a service (like ArcGIS Server or Map Server). Then essentially what you have is a URL (Uniform Resource Locator) which is a link to the location of your service. Much like http://maps.google.com/ and http://maps.yahoo.com/.
Many of the large online mapping companies have huge banks of servers and each company may use many open and closed source programs in combination to build and compile their data and serve it the user. One thing is for sure though. The technology systems that they use is extremely robust and reliable. They have the ability to receive thousands of commands a second from all over the world and serve the result of the command to your browser in a one quarter of second or less! The server technology behind these multi scale web maps is phenomenal!
I am certainly not an expert in server technology so please pardon me for being a little too general here! But hopefully you get a sense of how a 'map' server plays its roll in the map production cycle.
Q) Where do Google, Bing, Yahoo, MapQuest and Open Street Map get their data from?
A) The data behind the maps can be broken into three parts. Commercial, government and crowd sourced data. Some of the major commercial companies that provide data to the online mapping companies include Navteq http://www.navteq.com/. TomTom http://www.tomtom.com (formerly Tele Atlas). These are the two major global mapping providers that licence (or in some cases sell) their data to the online mapping providers. Companies like Geo Eye http://www.geoeye.com and Digital Globe http://www.digitalglobe.com/ provide much of the global satellite imagery that you see in the maps.
Many government sectors also provide data to the online mapping companies. This tends to be at medium to large scales (i.e. at more of a local/regional level where the commercial data may not cover that particular area or their accuracy may be questionable).
Of course a very popular and relatively new method of obtaining data is by using the crowd. Users like yourself can contribute data to sites like Open Street Map http://www.openstreetmap.org/ and Google (see http://www.google.com/mapmaker). This method of sourcing data is gathering some serious momentum as Open Street Map have proven and Google now have initiatives underway in Africa and other parts of the world where users can contribute to their maps.
I did forget to mention that some of the online mapping providers capture and compile some of their own data. Take Google Street View for example. Google took it upon themselves to capture this incredible never seen before data.
You will notice that the online mapping companies list many of their data sources for their maps at the bottom of each mapping service. Check them out when you get a chance!
Q) Why do they look like they do?
A) The style of each online multi scale web map is very different. Each provider has its own style. Bing has recently undergone a major change in style from a traditional looking online map to a single tone 'purple' looking map. Google have progressed their design over the years. Map Quest also recently 'revamped' their look. There is fierce competition between these online mapping providers and one way they can capture an audience is by the look of the map. Traditionally if users like the look of the map and the map functions well, i.e. it helps them locate a place and gets them from A to B then they will continue to return to that service. Styling these maps is very very difficult and I can't wait to start going into detail about it later as the blog progresses!
