OSM Merida

Extracting OpenStreetMap Data in QGIS 3

The OpenStreetMap (OSM) can be a good source of geospatial data for all sorts of features, particularly for countries where the government doesn’t provide publicly accessible GIS data, and for features that most governments don’t publish data for. In this post I’ll demonstrate how to download a specific feature set for a relatively small area […]

Final PostGIS Result

Measuring Polygon Overlap in QGIS and PostGIS

I was helping someone with a project this semester where we wanted to calculate overlap between two different polygon layers (postal code areas and grid cells) for over forty countries throughout the world. The process involved calculating the area of overlap and percentage of total overlap between each postal area and grid cell. We began […]


Place Names: Comparing Two Global Gazetteers

Gazetteers are directories of place names and locations, which are useful for: Identifying variations in place names Obtaining coordinates Locating a place within a hierarchy of places Generating lists of types of features For example, if you’re working with data that’s associated with specific cities, mountains, or bodies of water, and you have the names […]

The Map Reliability Calculator for Classifying ACS Data

The staff at the Population Division at NYC City Planning take the limitations of the American Community Survey (ACS) data seriously. Census estimates for tract-level data tend to be unreliable; to counter this, they aggregate tracts into larger Neighborhood Tabulation Areas (NTAs) to produce estimates that have better precision. In their Census Factfinder tool, they […]