The clear identification of the requirements for any GIS project is necessary before any data input procedures, and/or layer definitions, occur.

Global Coordinates provides relevant consultancy services for conducting “User Needs Analysis’ for succesful planning and execution of GIS based solutions.

Experience has shown that a less than complete understanding of the needs and processing tasks required for a specific project, greatly increases the time required to complete the project, and ultimately affects the quality and reliability of the derived GIS product(s).

In any GIS project a variety of data layers will be required. These must be identified before the project is started and a priority given to the input or digitizing of the spatial data layers. This is mandatory, as often one data layer contains features that are coincident with another, e.g. lakes can be used to define polygons within the forest inventory data layer. Data layers are commonly defined based on the needs of the user and the availability of data. They are completely user definable.

When considering the physical requirements of the GIS software it is important to understand that two types of data are required for each layer, attribute and spatial data. Commonly, data layers are input into the GIS one layer at a time. As well, often a data layer is completely loaded, e.g. graphic conversion, editing, topological building, attribute conversion, linking, and verification, before the next data layer is started. Because there are several steps involved in completely loading a data layer it can become very confusing if many layers are loaded at once.

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The proper identification of layers prior to starting data input is critical. The identification of data layers is often achieved through a user needs analysis. The user needs analysis performs several functions including : identifying the users; educating users with respect to GIS needs; identifying information products; priorizing data requirements and products; and determining GIS functional requirements. Cost benefit analysis with respect to hardware and software

Often a user needs assessment will include a review of existing operations, e.g.sometimes called a situational assessment, and a cost-benefit analysis. The cost-benefit process is well established in conventional data processing and serves as the mechanism to justify acquisition of hardware and software. It defines and compares costs against potential benefits. Most institutions will require this step before a GIS acquisition can be undertaken.

Most GIS projects integrate data layers to create derived themes or layers that represent the result of some calculation or geographic model, e.g. forest merchantability, land use suitability, etc. Derived data layers are completely dependant on the aim of the project.

Each data layer would be input individually and topologically integrated to create combined data layers. Based on the data model, e.g. vector or raster, and the topological structure, selected data analysis functions could be undertaken. It is important to note that in vector based GIS software the topological structure defined can only be traversed by means of unique labels to every feature.

(Acknowledgement: http://www.innovativegis.com/)