Symbol location accuracy using addresses/place names
Often when making a symbol map, we want to use specific geographic locations such as counties, cities, or even neighborhoods. In order to create a symbol map on Datawrapper, you need to upload your data with either
1) Address/Place Names or
Since most of us don't always have specific latitude and longitude data, we use place names to create our map. In this tutorial, we'll review how to ensure your symbols appear in the correct location on the map using address/place names.
For this example, we'll be creating a map of New York state's counties and how many farmers' markets each has. The first step in the process is to select the base map - in this case, New York State counties. Easy enough.
The next step is to add our data. This is where it can get tricky. When adding data using place names, try to be as specific as possible so that our geocoder is better able to locate places (though exact addresses are not necessary).
Geocoding is the process of automatically mapping a description of a location—such as a pair of coordinates, an address, or a name of a place—to its geographical coordinates. Sometimes it may seem like you get unexpected or unpredictable results from the geocoding process. Geocoders can't always be 100% reliable as there are often multiple places with the same name, and it doesn't know which one you're aiming for. Think of it like when you put an address into Google Maps - there are always multiple results, and the one you had in mind isn't necessarily the first one. A geocoder works the same, except you have no chance but to look through the list of search results to determine which one is correct - the geocoder always takes the first result. Again, it is helpful to be as specific as possible in the address definition.
Here are a few quick-reference examples for different types of locations:
Neighborhood: Williamsburg, Brooklyn, New York
City: New York City, New York
Zip Code: 11212, Kings County, New York
County: Kings County, New York
State/Land: New York State, USA
Let's take a look at three outcomes using our New York counties example in order from least accurate to most accurate:
1) Using Only County Names
In this example, the county name is ambiguous. Kings, for instance, could be a county, city, or neighbourhood anywhere in the US. It is visible in the map that many counties are missing symbols, and there are symbols located in the white space. The number of errors make this map completely unusable.
2) Using County AND State Names
In the second example, the county name + the state name is clearer, but again, Kings, New York could be either a town or a county (which happens to be a town in upstate New York). If you look closely, several counties are missing symbols and some counties have more than one symbol. This map is really still not ready for use.
3) Using County + the word 'County' AND State Name
The third map is perfect. In the last example, county name + "county" + state name (Kings County, New York) ensures that the geocoder knows we are referencing a county and is able to place all the symbols correctly with 100% accuracy. Feel free to zoom in on the maps and see if you can locate the errors.
In summary, when creating a symbol map, be sure to include specific location names when importing your data using addresses/place names. The more specific you are, the more likely the geocoding process will deliver accurate symbol placement.