So you have decided to install a surveillance system at your site. It may have been that the bad guys are breaking into cars in the parking lot or someone is helping themselves to equipment or products in the warehouse – for whatever reason you need to see what’s happening. Now what do you do next? How do you determine exactly what you need? It’s time to do the site survey. Here’s what you do:
How to Select the Resolution you will need
The resolution defines the detail that you will see. I have talked to a number of people who have video surveillance camera systems and find that the video that they stored is not clear enough to make out a person’s face. This is because they don’t have enough resolution. Now resolution is not only determined by the camera so be careful here. Sometimes you may get a good resolution camera, but then the resolution is lost when it’s stored in the recorder. A typical problem is that video is compressed so you can store many days in the recorder. Compression increases the amount of video you can store but decreases the resolution.
Resolution is important if you are trying to view a person’s face (or a license plate number) in a large area. This is especially true if the object you are trying to view takes up a small part of the overall picture. The wider the area you want to view the more resolution you need to see all the detail.
There was a study done by the US government that determined that you need 50 pixels per foot to identify a person’s face or read a license plate number. So if you have a 700 x 480 pixel camera it can view an area that is 14 feet wide (700 pixels/50 = 14). If you want to view a larger area, you need more pixels (higher resolution). A camera with a resolution of 1600 x 1200 can view an area that's about 32 feet wide. Take a look at http://www.kintronics.com/iqinvision/IQe3spec.htm for examples of high resolution IP cameras.