Blog 2: How Geocoding Works

Everyday I walk to Swem and sit at a desk and stare at a pile of Censuses. The most exciting part is that none of them are names Zimbabwe or Malawi or Ghana. Because these censuses are pre-independence and during colonialism the British, the Belgium, the Portuguese and the French and Spaniards gave some places different names then what we are used to. Ghana was the Gold Coast, Zimbabwe was Southern Rhodesia, Malawi was Nyasaland. Look at the picture posted below. You may not be able to tell but what I need from them is the European (Non-Native) population and the African (Native) population per colony, province/region (better known to data mapping nerds as ADM1, meaning Administrative Division 1–the second largest geographical division after the colony/country), region/district (ADM2–the second largest division), town/village (ADM3–the third largest division), and some include subdivisions/suburbs/wards (ADM4). Every colony separates its ADMs differently. Ghana, for example, goes: colony, province (Ashanti, Coast (West/East), Northern Territories  and (parts) Togoland), and town. As does the DRC (formerly Zaire). Here below, Southern Rhodesia is separated by district, town, suburb. Northern Rhodesia the other hand is divided by province, district, town.

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The town data is the most important because the borders of districts and the names can change a lot over time–esp. post-independence. Towns names may be different but they are located in the same place. To account for this, I used a database called geonames which is very familiar to the development communities’ geocoders (#AidData). Geonames recognizes the variant names of a town and spellings and gives me the current town’s name which I log and the longitude and latitude of the town. The fist image below is the home page of and I can pick a country and put in a town form the census. For instance, I chose Zimbabwe from the drown down bar and  then put in a town from the census such as Salisbury. In the second image, you see the results of the search. Salisbury ends up being renamed after independence as Harare–the capital of Zimbabwe. I know that I am choosing a town when the feature class description says: capital of a political entity, seat of an second/third order division, or populated place. I click the bubble P to the left of the name to get the third image and get the longitude and latitude in decimal form.