This involves a portable powered access point attached to a flexible mount, normally a tripod, which can then be used to position the AP in a variety of locations. This then allows the surveyor to verify the signal propagation using a passive survey. This type of survey may well be used in more complex environments such as warehousing or manufacturing. The benefit of the AP on a stick survey is that it allows you to produce more accurate wireless designs in complex environments.
Active Survey
This is the most thorough and accurate type of survey. It is similar to the passive survey in that the approach also requires the surveyor to walk around the site. The advantage of this over a passive survey is that an Active survey involves connecting to the test equipment to the local wifi network and measuring the throughout achieved, as well as things like roaming performance.
Passive Survey
This involves walking around and measuring radio characteristics on the site and recording them. The output is essentially a heatmap. The drawback is that although this survey measures signal strength and interference, the actual throughput achieved is still predicted rather than actually measured.
Predictive Survey
Sometimes called a Desktop survey, this uses complex software combined with accurate site drawings to generate a wireless design. Cheaper but less reliable than site based surveys.
Above is a typical 3d predictive survey of a medium sized warehouse.