The sequence of GIS work

GIS work follows a sequence:

• Spatial data input: either from data suppliers (checking that their formats are compatible), or by digitising and scanning paper maps (scanners use CCDs, charge-coupled devices).
• Entering attribute data: the properties of features, like a road's width and surface, from records, censuses and surveys.
• Data verification and editing: compare the plots with the originals; fix omissions, wrong scale and distortion; and build topology (the connections between features).
• Data conversion: usually from vector to raster for analysis, or from raster to vector to reduce storage.
• Linking spatial and attribute data: exact matching by a common key (like a district code); hierarchical matching by aggregating small areas into larger ones; or fuzzy matching by overlay, when boundaries do not line up exactly.

Get it in, get it right, join it up.