It is sometimes essential to be able to create areas based on administrative divisions, such as states, counties, county equivalents or zip codes, as shown in this image:
This can enable you to:
- Produce comparative analyses of catchment areas against a reference area (e.g. a particular county)
- Create catchment areas based on an administrative division (zip codes, states, etc.)
- See a visual comparison of the existing administrative division with your catchment areas
Downloading data on administrative divisions #
First of all, you have to download data on the administrative divisions that are of interest. For example, you could visit the Opendatasoft website. To access it directly, use the following links:
Make sure that you filter the search results in Opendatasoft, so that you only download the data on the areas that interest you. If you try to display more than a few hundred areas on the OALLEY map, it will be significantly slowed down and user experience could be negatively impacted.
Before downloading the data for your areas, you can view them and select the ones that interest you using the “Map” tab:
You can select your areas in two ways:
- By using filters (keywords, county names, etc.)
- By drawing a polygon on the map to select them straight from the map, as shown:
Use the “Export” tab to download the date for your chosen areas in KML format:
To download the selected areas, click on “Only the X selected records” in the KML line:
For areas in other countries, you might be able to find data by searching the internet, for example by using the keyword “KML”, along with the area type and country in question.
Importing your area data #
Create a new folder for your areas and import the KML file containing the areas’ data by dragging the file and dropping it onto the map. To find out more about importing MKL files, go to “Import areas in KML format”.
To go further:
- Extending an area
- Reducing an area
- Analyzing the population of an area
- Importing your own data on the map