(I hope I'm posting this in the right place...)

Recently, a task fell upon a co-worker and I to come up with a somewhat complex project (complex for me, anyway). I am honestly at a loss as how to proceed with it, so I'm asking experienced developers for their input and advice.

Here's the project:
Create a web interface for displaying multiple variables visually, like on a map.
The variables would come from a database, i.e. MySQL or something similar. The user would select whichever options they would wish to see, such as GPS coordinates plotted out over a timeframe of several days. Once selected, an on-screen map would show these points plotted along with additional details specific to that point, either as a pop-up rollover or in a sidebar (similar to GMaps where they list various options on the side).
Since this will also include multiple user data, another option would allow users to see things such as crowd or traffic density in the form of a color range map overlayed onto a regular map. Again, the user may choose various options, such as time of day, etc, to pinpoint specific moments in time.

There are other options, but this is pretty much the jist of it. If you need more information please feel free to ask. However, because of the nature of this project I may not be able to answer questions with specific details. Don't worry, I do not work for the NSA.

As I mentioned earlier, I'm curious to see how a savvy web developer would go about accomplishing this. Would it involve ASP, PHP or some other server-side code? Would the databases be MySQL or something different? Would any other code be involved to execute these commands, i.e.: javascript, etc?

Thanks in advance for any of your feedback!