The OpenCellID project still needs a lot of contribution for completing the database.
Some of the reasons are
- every day new GSM towers are built, in these days for example for the relatively new LTE networks
- in most of the countries many cell towers are still waiting for being detected: currently the OpenCellID database holds less than 5 million base stations, whereas big commercial databases have more than 40 million base stations available.
This Wiki page lists measures that might improve the growth rate of the OpenCellID database.
Collaboration with App developers
The most powerful tool for growing the contributor database is probably teaming up with publishers of smartphone apps.
The best suitable apps are those that need GPS anyhow, because in this case the relatively high power consumption of the GPS receiver doesn't matter because it is on anyhow.
here you can find an Android library that can easily be integrated into any Android app. It runs completely in the background and does not need any attention of the app user.