Geospatial search, frequently referred to as geocoding, is the process of matching an address to its corresponding geographic coordinates. There's nothing inherent in the words we use to describe an address that conveys its position at some coordinates on earth, such as a latitude,longitude. Making the leap from text to coordinates is an intricate and challenging process. Lucky for you, Mapzen has done all the hard work and made it accessible though a free web service.
The Mapzen Search request takes the form of `https://search.mapzen.com/v1/search?api_key={your-api-key}`, where the JSON inputs inside the `{}` include search parameters such as the text to find and filtering options. Note that you must append your own Mapzen Search API key to the URL, following &api_key= at the end.
In the simplest search, you can provide only one parameter, the text you want to match in any part of the location details. To accomplish this, build a query where the `text` is set to the item you want to find.
For example, if you want to find a [YMCA](https://en.wikipedia.org/wiki/YMCA) facility, here's what you'd need to append to the base URL of the service, `search.mapzen.com`.
Spelling matters, but not capitalization when performing a query with Mapzen Search. You can type `ymca`, `YMCA`, or even `yMcA`. See for yourself by comparing the results of the previous search to the following:
Note that the results are spread out throughout the world because you have not given your current location or provided any other geographic context in which to search.
If you are looking for places in a particular region, or country, or only want to look in the immediate vicinity of a user with a known location, you can narrow your search to an area. There are different ways of including a region in your query. Mapzen Search currently supports three types: country, rectangle, and country.
Sometimes your work might require that all the search results be from a particular country. To do this, you can set the `boundary.country` parameter value to the alpha-2 or alpha-3 [ISO-3166 country code](https://en.wikipedia.org/wiki/ISO_3166-1).
Now, you want to search for YMCA again, but this time only in Great Britain. To do this, you will need to know that the alpha-3 code for Great Britain is *GBR* and set the parameters like this:
To specify the boundary using a rectangle, you need latitude, longitude coordinates for two corners of the bounding box (the mininum and the maximum latitude, longitude).
For example, to find a YMCA within the state of Texas, you can set the `boundary.rect.*` parameter to values representing the bounding box around Texas: min_lon=-106.65 min_lat=25.84 max_lon=-93.51 max_lat=36.5
Sometimes you don't have a rectangle to work with, but rather you have a point on earth—for example, your location coordinates—and a maximum distance within which acceptable results can be located.
In this example, you want to find all YMCA locations within a 35-kilometer radius of a location in Ontario, Canada. This time, you can use the `boundary.circle.*` parameter group, where `boundary.circle.lat` and `boundary.circle.lon` represents your location in Ontario and `boundary.circle.radius` is the acceptable distance from that location. Note that the `boundary.circle.radius` parameter is always specified in kilometers.
If you're going to attempt using multiple boundary types in a single search request, be aware that the results will come from the intersection of all the boundaries. So if you provide regions that don't overlap, you'll be looking at an empty set of results. You've been warned. Here's an image of how it works:
Many usecases call for the ability to promote nearby results to the top of the list, while still allowing important matches from farther away to be visible. If that's your conundrum, here's what to do.
Search will focus on a given point anywhere on earth, and results within 100 kilometers will be prioritized higher, thereby surfacing highest in the list. Once all the nearby results have been found, additional results will come from the rest of the world, without any further location-based prioritization.
Looking at the results, you can see that the few locations closer to this location show up at the top of the list, sorted by distance. You also still get back a significant amount of remote locations, for a well balanced mix. Because you provided a focus point, Mapzen Search can compute distance from that point for each resulting feature.
Going back to the YMCA search you conducted with a focus around a point in Sydney, the results came back from distant parts of the world, as expected. But say you wanted to only see results from the country in which your focus point lies. You can combine that same focus point in Sydney with the country boundary of Australia like this.
The results below look very different from the ones you saw previously with only a focus point specified. These results are all from within Australia. You'll note the closest results show up at the top of the list, which is facilitated by the focus parameter.
If you are looking for the nearest YMCA locations, and are willing to travel no farther than 50 kilometers from your current location, you likely would want the results to be sorted by distance from current location to make your selection process easier. You can get this behavior by using `focus.point` in combination with `boundary.circle.*`. You can use the `focus.point.*` values as the `boundary.circle.lat` and `boundary.circle.lon`, and add the required `boundary.circle.radius` value in kilometers.
Mapzen Search brings together data from multiple open sources and combines a variety of place types into a single database, allowing you options for selecting the dataset you want to search.
The search examples so far have returned a mix of results from all the data sources available to Mapzen Search. Here are the sources currently being searched:
If you use the `sources` parameter, you can choose which of these data sources to include in your search. So if you're only interested in finding a YMCA in data from OpenAddresses, for example, you can build a query specifying that data source.
If you wanted to combine several data sources together, set `sources` to a comma separated list of desired source names. Note that the order of the comma separated values does not impact sorting order of the results; they are still sorted based on the linguistic match quality to `text` and distance from `focus`, if you specified one.
In Mapzen Search, place types are referred to as `layers`, ranging from fine to coarse. The Mapzen Search layers are derived from the hierarchy created by the gazetteer [Who's on First](https://github.com/whosonfirst/whosonfirst-placetypes/blob/master/README.md) and can be used to facilitate coarse geocoding. Here's a list of the types of places you could find in the results, sorted by granularity:
****TO DO: Describe fine and coarse geocoding, gazeteer. ***
If you are building an end-user application, you can enable `/autocomplete` alongside the `/search` to add real-time feedback to help users find what they are looking for more easily, without requiring them to type the entire search term. Typically, the user starts typing and a drop-down list appears where they can choose the term from the list.
