Geographical Information Systems (GIS) is the body of tools for thematic mapping and spatial analyses. The latter refers to spatio-temporal and statistical analyses.
GIS may be applied graphically in the form of grid or raster and/ or linear or vector-based mapping. In this study, we combined both forms of information whenever data permits.
Specifically, the GIS approach can be utilized for the following tasks:
- Base mapping with and/or around administrative units,
- Grouping of map themes by categories and sub-categories,
- Breakdown of legends into variables and their corresponding characteristics or attributes,
- Overlaying and/or correlation of themes of different types and forms,
- Change detection or multitemporal studies for monitoring conditions.
In addition to the maps produced by GIS software, comparative matrices can also be generated. These matrices complement the maps by way of:
- Spatial databases, based on which logical and/ or numerical operations are performed,
- Comparison across spatial units, for example nations, regions, sub-regions, provinces, cities/municipalities as well as barangays,
- Comparison across different themes by category of hazards and disasters,
- Merging of qualitative with quantitative assessments.
In this study, risk is calculated through the UNDP formula:
As mentioned, hazards are grouped according to the abovementioned category of factors which are at play. Risk, so calculated by category, is then mapped by province. As such, it represents the compounding influence and effect of these specific variables or indices by category of factors.