Dilution of Precision (DOP) is one of the most fundamental quality indicators for GNSS users. Even though there are some limitations such as described here.

DOP can be very important for planning GNSS surveys as well as performing quality control or dignosing poor results. Current DOP simulators usually rely on the broadcast ephemeris which only includes existing satellites. I wanted to be able to add/remove satellites as well as move satellites around to see how it affected the DOP values. This allows you to simulate what your DOP would be like if you had 80+ satellites visible. Although this might be a little silly, the future is looking friendly. Soon there will be more than four constellations each with 24+ satellites each!

The result of my efforts can be seen here. A screen shot is shown below:
GNSS DOP Simulator

For the simulator, DOP is computed directly in the local ENU frame using the satellites elevation angle and azimuth.

To create the tool I used some great freely available javascript libraries including:

The numeric library is used for inverting the normal matrix which is very speedy even for large matrices.

Anyway, let me know what you think. Hope you like it!