OE-6.5 Process of GIS & Geospatial Analysis

Work through these

• Data sources for GIS

  Where data actually comes from, which is most of the work in a real project. Existing data is usually cheaper and worse than collecting your own, and that decision comes first.

• Encoding raster data, vector data and attribute data

  Getting each of the three data types into the system. Attribute encoding is the tedious half and the one that determines whether the analysis below is possible.

• Linking spatial and attribute data

  Making the join from the earlier topic real, in practice. A mismatch between the two halves is the most common reason a dataset cannot be used.

• Database query

  Asking questions of the data, by attribute and by location. The second kind is what a geographic system offers that a database does not.

• Geospatial measurement

  Distance, area and shape computed from the geometry. Watch for the projection, because the same feature has different measurements in different ones.

• Overlay operations

  Combining layers to answer a question neither answers alone. It is the operation the whole field is known for and the one worth being able to do by hand on paper.

• Network analysis

  Analysis along connected lines, for routes and flows. It is a different mathematical problem from the overlay above and needs its own data preparation.

• Surface analysis

  Working with a continuous surface, usually terrain: slope, aspect and visibility. This is where the height data from the earlier topic is used.

• Integration of GIS and remote sensing

  Bringing the two halves of the subject together, which is where it has been heading. Imagery supplies the observations and the system supplies the context to reason about them.