Downgrading gaul datasets

From Giews

This page is full of assumptions. Each assumption is a proposal. This page is written to start the discussion about how to deal with the different levels of Gaul.

• A gaul 3 dataset can be used to show on gaul 3,2,1 and 0 level.
• A gaul 2 dataset can be used to show on gaul 2,1 and 0 level.
• A gaul 1 dataset can be used to show on gaul 1 and 0 level.
• A gaul 0 dataset can be used to show on gaul 0 level.

Using a Gaul dataset from a certain level to show information on less detailed level is called downgrading a dataset (the level of detail is downgraded). Downgrading a dataset is reverse linear with zooming in into the detail level of the dataset.

A downgraded dataset can be used to serve as a base for a table, map or chart. Therefore Postgis is not only used to downgrade a dataset. Using Postgis for downgrading a dataset is a next complicated issue to investigate and can be done. With or without Postgis, Fenix needs to be able to downgrade datasets. Downgrading a dataset with Postgis is something to sort out later.

Within Fenix, Gaul is not the layer, but Gaul has, specifies 4 layers: Gaul0,1,2 and 3. Fenix will consider gaul as just 4 layers. Fenix will have its own algorithm to downgrade from a Gaul layer to a lower layer. The algorithm will be as much as possible based on calculating the averages.