Asmat Ali
Assistant Director
Survey of Pakistan
SDIs have different levels. It can be developed at corporate level, local level, state level, national level (NSDI), regional level and global level. Their characteristics vary with the level at which they are developed and this level includes administrative as well as geographical level due to different needs at different levels. Pickels (2004) and de Man (2006) argue for the same thought, “SDIs are also susceptive to geopolitical, economic, and socio-cultural issues and all the associated opportunities and threats of cyber spaces and interactions”, (Pickels 2004), “SDIs and other kinds of information infrastructure alike –are different at different spatial (or geographical) levels because of differentiated social contexts”, (de Man 2006).
Figure 1: Hierarchical nature of SDI (Rajabifard et al. 2002)
It is clear from above model developed by Rajabifard that Global SDI is based on Regional SDI, Regional SDI is based on National SDI, and National SDI is based on State SDI and so on. But it does not reflect the scale of problems that how problems would vary along this hierarchy in case of detailed data at different levels. It is believed that moving "up" in the SDI hierarchy will bring more socio-technical problems.
For example problems at State SDI will be less than problems at National SDI. One reason is that upper-level SDIs inherit from lower-level SDIs. Second reason is there will be many state SDIs, means many organizations will be involved, and in the case of more organizations, legal, technical, and cultural problems will arise. Every state has its own norms, rules and regulations. One state may categorise a certain type of information as classified and may not permit every one to access it where as other state may offer open access to the same information. For example, Goa is an Indian state, the editor of Coordinates in its issue of August 2007 envisions, “Goa being a costal state falls under the secret category and its maps can not be put on a network”. Similarly, moving from “more detailed data” to “less detailed data” will offer significant technical problems. For instance in case of coastal lines, the generalization rule adopted by different states may be different. Therefore, the gravity of the situation will become more problematic and increase while going up in SDI hierarchy which is presented graphically in figure 2.
Figure 2: Hierarchical nature of SDI (after Rajabifard et al. 2002)
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