Using polygon overlays for proportional census estimates
PostgreSQL functions abound for the aggregation of tabular data, including sum, count, min, max, and so on. PostGIS as a framework does not explicitly have spatial equivalents of these, but this does not prevent us from building functions using the aggregate functions from PostgreSQL in concert with PostGIS's spatial functionality.
In this recipe, we will explore spatial summarization with the United States census data. The US census data, by nature, is aggregated data. This is done intentionally to protect the privacy of citizens. But when it comes to doing analyses with this data, the aggregate nature of the data can become problematic. There are some tricks to disaggregate data. Amongst the simplest of these is the use of a proportional sum, which we will do in this exercise.
Getting ready
The problem at hand is that a proposed trail has been drawn in order to provide services for the public. This example could apply to road construction...
