Map production using aerial photographs / satellite imagery

Advantages / Limitations:

	High quality and updated maps can be produced in a short period of time. Further analysis of satellite images can be done using the right GIS software, (e.g. land cover analysis). Ease with which the maps can be stored digitally and the subsequent quick reproduction or replication of the maps whenever they are needed. Digital spatial datasets can be easily exchanged with any institution or organization. Field surveys are reduced to the level of spot-checks, therefore time-consuming surveys covering the entire area are no longer necessary. Aerial images can be used as a basis for discussing the local conditions and situation during participatory planning exercises. The technical development of computer’s capabilities and capacities grows rapidly and opens up new opportunities for processing large amounts of high resolution satellite imagery.
	Costs of the initial purchase of satellite images may be compounded by additional costs involved in regularly purchasing updated satellite images. Considerable effort is required to manage the data and information. For example, the inclusion of meta databases, correct documentation of technical procedures, selection of data that needs to be exchanged both within and between institutions and determining which data should be published and made freely accessible: all has to be planned and managed. Highly qualified and specialized personnel are needed to process, interpret and verify the data. The personnel need to have a sound knowledge of rectification procedures, projection systems, cartographic skills, planning techniques and GIS functionality skills in order to be able to produce good quality maps. Qualified personnel are often difficult to recruit. Personnel need specialized training that in turn increases their market value. Low public sector pay means that they cannot be retained. More affluent private sector companies subsequently recruit trained personnel which again leads to a shortage! The higher the resolution of the satellite images, the higher the volume of data that has to be processed, e.g. doubling the ground resolution implies a quadrupling (i.e. four times) higher volume of digital data. This often implies that computer hardware has to be upgraded or new equipment has to be purchased to handle the data volumes; thus further increasing the overall costs involved in producing accurate maps. Appropriate GIS software capable of handling the data and information has to be purchased.