Updating maps using Global Positioning Systems (GPS)

Advantages / Limitations:

	Quick way of accurately updating maps. Ease with which locations for features in maps can be determined with a high degree of accuracy. Existing maps can be quickly updated to add new features such as road networks, schools, water supply systems, etc. GPS surveys can be undertaken in areas that are vulnerable to regular cloud cover, a fact that often limits the use of satellite images.
	For GPS to be useful it requires a high degree of accuracy (including the post-processing of GPS data). High-resolution GPS surveys require sophisticated and expensive technologies as well as highly trained staff. Geodetic surveys require a high degree of accuracy if they are to prove useful. Distortion of satellite signals can also reduce the area that can be surveyed (e.g. forests, dense urban areas, and tunnels, hill formations) The collection of map data is time-consuming, especially if the survey is to cover a wide area or if the level of detail of the survey objects is very high. Additional information (attribute data) has to be collected during the survey Classification procedures have to be similar for all surveys (e.g. density of trees determined to classify a forest area)