Important Issues for creation of data
- Need Analysis: The client will have certain ideas for the data development. However, in most of the cases he may not be fully clear or aware of what best can be done. It is the job of the GIS analyst to carefully assess the requirements of the user and suggest what is best suited for his needs. Such an analysis will help in evolving the needed specifications.
- Cost: With any type of information system, careful planning prior to data acquisition or data creation generally increases the degree of success and utility. Lack of planning increases the possibility of a mismatch between a system’s capabilities and user needs, resulting in wasted money. The cost of data development is quite high and the customer must be sensitised and shown a method by which he can achieve his aim within his estimate.
- Accuracy: Another major issue for data creation relates to accuracy, completeness and timeliness of the. Digitising information for inclusion in a GIS is not simple and straightforward. As information is included or excluded to fit with the application, the accuracy and completeness of that information may be compromised. In addition the conversion of existing records, without verifying the accuracy of the information with the data subject, may mean that the quality of the newly digitised information is poor as it is out-of-date or incomplete.
- Scaleability Issues: It is important to develop data in such a manner that future expansion is possible. If this is not considered during data creation then different kinds of spatial data pertaining to the same area cannot be attached with each other due to difference in projection systems and attribute information.
- Lack of quality and availability of base data: Data quality is essential when a GIS is used to make decisions that, potentially, could adversely impact the data subject. Without accurate information, any potential operational efficiency or benefits, may be compromised. Lots of data creation effort gets stuck because either the base data being unavailable or of very poor quality.
- Permissions from regulating authorities: This policy on data development needs a relook.
- Standards/Formats: A standard format needs to be developed for spatial data as data conversion from different formats causes a lot of data loss and the quality of the data gets reduced.
- Symbology: Standard sets of symbols should
be developed to use with all kinds of applications using GIS.
Data Organisation
Structuring of the database and their indexing and other related issues play an important role in the GIS application development lifecycle. Just as in any normal database activity, the GIS database also needs to be designed so as to cater to the needs of the application that proposes to utilise it. Apart from this the design would also:
- Provide a comprehensive framework of the database.
- Allow the database to be viewed in its entirety so that interaction and linkages between elements can be defined and evaluated.
- Permit identification of potential bottlenecks and problem areas so that design alternatives can be considered.
- Identify the essential and correct data and filter out irrelevant data
- Define updation procedures so that newer
data can be incorporated in future.
The design of the GIS database will include three major elements
- Conceptual design, basically laying down the application requirements and specifying the end- utilisation of the database. The conceptual design is independent of hardware and software and could be a wish-list of utilisation goals.
- Logical design, which is the specification of the database vis-a-vis a particular GIS package. This design sets out the logical structure of the database elements determined by the GIS package.
- Physical design, which pertains to the
hardware and software characteristics and requires consideration
of file structure, memory and disk space, access and speed etc.
Data stored in an inefficient framework would cause performance overheads. The success or failure of a GIS project is determined by the strength of the design and a good deal of time must be allocated to the design activity.
Application development
GIS application development is basically customisation of existing GIS software to meet specific needs. The applications may be as simple as a set of preferences that are stored for each user group or individual. Or they may be a very complex queries that selects a group of layers, identifies features of interest based on attribute ranges, creates variable width buffers, performs a series of overlays and produces a hard copy map. In either case, an application is required to convert the user’s ideas into a usable, stable product. In a large number of cases after using simple application, the users become more experienced with GIS and then they require more complex applications. The initial needs assessment will contain some applications of a complex nature, however the majority of initial applications will be straightforward, using the basic functionality that is part of every commercial GIS (e.g., query and display). The more complex applications usually are not supported by the basic functions of a GIS but must be programmed using the GIS macro language or other programming language. This section identifies several categories of applications that can be prepared by users and how overall requirements change over time.
Applications are usually built on existing GIS packages. These packages provide the functionality common to all user disciplines. Commercial GIS packages tend to focus on the common or basic applications. When it comes to specialised uses, application development fills the needs for functionality. Though there is a great deal of commonalty in the basic spatial queries and display functions, there is still a need for other advanced applications. We need additional applications because needs are different between organisations.