The range of metrics (or indicators) being used to measure research impact is growing and the issues around them are complex. If you are interested in exploring this area there is an excellent resource produced by 3 Irish academic libraries: MyRI Measuring your Research Impact.
The tutorial is particularly recommended: it is very thorough, considers all the pros and cons of the different metrics and has short videos of academics discussing how they are using (or not using) metrics. The MyRI tutorial is also available for re-use and adaptation under a Creative Commons Attribution-Non-Commercial-Share Alike 3.0 licence.
Swansea University has subscriptions to many of the products mentioned (you will need to click onto the “Online” tab to get the link that routes via our login):