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Geoinformation for Disaster and Risk Management - ISPRS

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Tiered conceptual framework <strong>for</strong> population<br />

estimation<br />

A tiered conceptual framework is proposed <strong>for</strong> the<br />

Ahmedabad case study, which is an applicationdriven<br />

approach, aimed at developing population<br />

data <strong>for</strong> input to risk model parameters. The selected<br />

levels correspond to the operating unit of analysis,<br />

ranging from postcode/district/city boundaries <strong>for</strong><br />

risk-sensitive planning, to a single building <strong>for</strong><br />

response <strong>and</strong> recovery missions. This framework,<br />

which may ultimately be st<strong>and</strong>ardised <strong>for</strong> other<br />

cities, poses a number of technical challenges.<br />

Figure 1: Examples of buildings affected by the 2001 Gujarat earthquake:<br />

(Left) heavily damaged residential building,<br />

(Right) multi-storey building that has fallen on one side (Bhuj, India) (Image courtesy by M. Markus, 2001)<br />

For each level, the relevant data have to be identified,<br />

their availability verified, <strong>and</strong> their accuracy<br />

evaluated. For example, data from Indian Census are<br />

only updated on a decadal basis. In order to integrate<br />

census in<strong>for</strong>mation with other data such as remote<br />

sensing imagery, the relevant census data should be<br />

projected to match the image acquisition year.<br />

Moreover, the significance <strong>and</strong> accuracy of Census<br />

data as well as other statistical data have to be<br />

carefully evaluated.<br />

The assumption that data <strong>and</strong> in<strong>for</strong>mation reflect<br />

reality should be h<strong>and</strong>led with care, as despite<br />

ef<strong>for</strong>ts to identify uncertainty, residual uncertainties<br />

will always remain. Cautious evaluation of available<br />

data that includes cross calculation <strong>and</strong> statistical<br />

analysis should lead to a data product that can be<br />

called the most likely status.<br />

In addition to data-related uncertainties, modelbased<br />

uncertainties also need to be considered. The<br />

modelling of population is typically based on<br />

relationships that are assumed to be true <strong>for</strong> the test<br />

site (<strong>for</strong> example, number of people resident at<br />

91

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