In terms of strategic planning the external analysis step can be very difficult. I see three reasons for that: Basically this analysis can be described as badly structured matter, which does not know a definitive solution. Due to the large amount of data the selection of relevant information remains a problem. To identify chances and threats for the organisation it is requested to analyse both current situation as well as possible developments. Hence the uncertainty of forecasts represents a third reason.
In particular the identification of potential competitors as well as the identification of measure by existing competitors can be hard. Annual reports, websites and analyst reports might be a good idea to start and to explain the past, but how about the future? It is possible to identify invaders to your industry?
Very often new companies (invaders) try to establish an organisational fundament during their market development steps; hence they offer new positions. Other companies, in particular those that want to enter a new market, try to hire people with a network within this particular market. But most electronic job exchanges have a free description field to search for single words or specific terms. Use this and you might be able to identify those organisations, which just have started to enter your industry segment.