Twitter offers developers two ways of accessing data about tweets. One way, the public Search API, allows developers to query Twitter for recent tweets about a particular topic. The Search API has significant limitations when it comes to achieving full coverage. For example, tweets are filtered for "quality" and are limited to 1,500 tweets from the last 5-7 days. We use the Search API for our individual snapshot reports (both the free and the full $20 versions). These are great if you're looking for a quick overview of recent tweets, but will not include anything more than a week old and does not always index the full dataset.
But when you want full coverage access to old or new tweets, you need something more comprehensive than our snapshot reports. The second way to access tweets is through Twitter's commercial data streams (formerly Gnip). This means we can deliver the highest quality Twitter data available, full-fidelity and in real time. Our TweetReach by Union Metrics Pro Trackers are built on the real-time PowerTrack stream and include full coverage of all tweets as they are posted - no limits - for your search terms. Our historical analytics are built on the real-time Search API, and includes access to the most complete Twitter archive available anywhere, dating back to March 2006. Both our real-time, ongoing Trackers and Union Metrics Echo are premium products built on full-fidelity Twitter streams directly from Twitter.
If you have any questions about what tweets we can access and how, please let us know.