21 KiB
Pelias: Finding places
Geospatial search, commonly referred to as geocoding, is the process of matching an address to its corresponding geographic coordinates.
There's nothing inherent in the language we use to describe a physical address that allows us to convert that human readable sentence in to a format that a computer can understand, such as 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 web service.
All Pelias requests share the same format:
https://search.mapzen.com/v1/search?text=London&api_key=
\___/ \_______________/\__/\_____/\__________/\_______/
| | / | | |
scheme domain version path query authentication token
In addition, you can search at https://search.mapzen.com/v1/search/structured to look for individual components of a location.
Pelias works over HTTPS and HTTP. You are strongly encouraged to use HTTPS for all requests, especially for queries involving potentially sensitive information, such as a user's location or search query.
Search the world
In the simplest search, you can provide only one parameter, the text you want to match in any part of the location details. To do this, build a query where the text parameter is set to the item you want to find.
For example, if you want to find a YMCA facility, here's what you'd need to append to the base URL of the service, search.mapzen.com.
Note the parameter values are set as follows:
| parameter | value |
|---|---|
api_key |
get yours here |
text |
YMCA |
Clicking the link above will open a file containing the best matching results for the text YMCA. You will notice the data is in a computer-friendly format called GeoJSON, which may be hard for humans to read in some browsers.
You can install a plug-in for your browser to display JSON in a more formatted manner. You can search the web store for your browser to find and install applicable products.
In the example above, you will find the name of each matched locations in a property named 'label'. The top 10 labels returned were:
- YMCA, Bargoed Community, United Kingdom
- YMCA, Nunspeet, Gelderland
- YMCA, Belleville, IL
- YMCA, Forest City, IA
- YMCA, Fargo, ND
- YMCA, Taipei, Taipei City
- YMCA, Orpington, Greater London
- YMCA, Frisco, TX
- YMCA, Jefferson, OH
- YMCA, Belleville, IL
Spelling matters, but not capitalization when performing a query with Pelias. You can type ymca, YMCA, or even yMcA. See for yourself by comparing the results of the earlier 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.
Search for a component of a location
With the text parameter, your search is composed of all the items in one string. With structured geocoding, you can search for individual components of a location.
Structured geocoding accepts one or more of the following parameters:
- address
- neighbourhood
- borough
- locality
- county
- region
- postalcode
- country
Structured geocoding also supports the other parameters from search, allowing you to filter and prioritize your results.
For more information on how to search this way, see Structured geocoding.
Set the number of results returned
By default, Pelias results 10 places, unless otherwise specified. If you want a different number of results, set the size parameter to the desired number. This example shows returning only the first result.
| parameter | value |
|---|---|
api_key |
get yours here |
text |
YMCA |
size |
1 |
If you want 25 results, you can build the query where size is 25.
Narrow your 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. Pelias supports three types: country, rectangle, and circle.
Search within a particular 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.
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:
/v1/search?api_key=your-mapzen-api-key&text=YMCA&boundary.country=GBR
| parameter | value |
|---|---|
api_key |
get yours here |
text |
YMCA |
boundary.country |
GBR |
Note that all the results are within Great Britain:
- YMCA, Bargoed Community, United Kingdom
- YMCA, Orpington, Greater London
- YMCA, Erdington, West Midlands
- YMCA, Malvern CP, United Kingdom
- YMCA, Ancoats, Greater Manchester
- YMCA, Carmarthen Community, United Kingdom
- YMCA, Halebank, Cheshire
- YMCA, Brightlingsea CP, United Kingdom
- YMCA, Lenton Abbey, Nottinghamshire
- YMCA, Old Clee, Lincolnshire
If you try the same search request with different country codes, the results change to show YMCA locations within this region.
/v1/search?api_key=your-mapzen-api-key&text=YMCA&boundary.country=USA
Results in the United States:
- YMCA, Belleville, IL
- YMCA, Forest City, IA
- YMCA, Fargo, ND
- YMCA, Frisco, TX
- YMCA, Jefferson, OH
- YMCA, Belleville, IL
- YMCA, Chapel Hill, NC
- YMCA, West Lampeter, PA
- YMCA, Bremerton, WA
- YMCA, Westerly, RI
Search within a rectangular region
To specify the boundary using a rectangle, you need latitude, longitude coordinates for two diagonals of the bounding box (the minimum 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
Tip: You can look up a bounding box for a known region with this web tool.
| parameter | value |
|---|---|
api_key |
get yours here |
text |
YMCA |
boundary.rect.min_lat |
25.84 |
boundary.rect.min_lon |
-106.65 |
boundary.rect.max_lat |
36.5 |
boundary.rect.max_lon |
-93.51 |
- YMCA, Austin, TX
- YMCA, Frisco, TX
- Y.M.C.A, Fort Worth, TX
- YMCA, Rockwall, TX
- YMCA, Missouri City, TX
- YMCA, Northshore, TX
- YMCA, Austin, TX
- YMCA, Tulsa, OK
- YMCA, Los Alamos, NM
- YMCA, Tulsa, OK
Search within a circular region
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 is 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.
| parameter | value |
|---|---|
api_key |
get yours here |
text |
YMCA |
boundary.circle.lat |
43.818156 |
boundary.circle.lon |
-79.186484 |
boundary.circle.radius |
35 |
You can see the results have fewer than the standard 10 items because there are not that many YMCA locations in the specified radius:
- YMCA, Toronto, Ontario
- YMCA, Markham, Ontario
- YMCA, Toronto, Ontario
- Metro Central YMCA, Toronto, Ontario
- Pinnacle Jr YMCA, Toronto, Ontario
- Cooper Koo Family Cherry Street YMCA Centre, Toronto, Ontario
Specify multiple boundaries
If you're going to try 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.
Prioritize results by proximity
Many use cases 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. Pelias allows you to prioritize results within geographic boundaries, including around a point, within a country, or within a region.
Prioritize around a point
By specifying a focus.point, nearby places will be scored higher depending on how close they are to the focus.point so that places with higher scores will appear higher in the results list. The effect of this scoring boost diminishes to zero after 100 kilometers away from the focus.point. After all the nearby results have been found, additional results will come from the rest of the world, without any further location-based prioritization.
To find YMCA again, but this time near a specific coordinate location (representing the Sydney Opera House) in Sydney, Australia, use focus.point.
| parameter | value |
|---|---|
api_key |
get yours here |
text |
YMCA |
focus.point.lat |
-33.856680 |
focus.point.lon |
151.215281 |
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, Pelias can compute distance from that point for each resulting feature.
- YMCA, Redfern, New South Wales [distance: 3.836]
- YMCA, St Ives (NSW), New South Wales [distance: 14.844]
- YMCA, Epping (NSW), New South Wales [distance: 16.583]
- YMCA, Revesby, New South Wales [distance: 21.335]
- YMCA, Kochâang, South Gyeongsang [distance: 8071.436]
- YMCA, Center, IN [distance: 14882.675]
- YMCA, Lake Villa, IL [distance: 14847.667]
- YMCA, Onondaga, NY [distance: 15818.08]
- YMCA, 's-Gravenhage, Zuid-Holland [distance: 16688.292]
- YMCA, Loughborough, United Kingdom [distance: 16978.367]
Combine boundary search and prioritization
Now that you have seen how to use boundary and focus to narrow and sort your results, you can examine a few scenarios where they work well together.
Prioritize within a country
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.
| parameter | value |
|---|---|
api_key |
get yours here |
text |
YMCA |
focus.point.lat |
-33.856680 |
focus.point.lon |
151.215281 |
boundary.country |
AUS |
The results below look different from the ones you saw before 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 helped by the focus parameter.
- YMCA, Redfern, New South Wales [distance: 3.836]
- YMCA, St Ives (NSW), New South Wales [distance: 14.844]
- YMCA, Epping (NSW), New South Wales [distance: 16.583]
- YMCA, Revesby, New South Wales [distance: 21.335]
- YMCA, Larrakeyah, Northern Territory [distance: 3144.296]
- YMCA, Kepnock, Queensland [distance: 1001.657]
- YMCA, Kings Meadows, Tasmania [distance: 917.144]
- YMCA, Katherine East, Northern Territory [distance: 2873.376]
- YMCA, Sadadeen, Northern Territory [distance: 2026.731]
- YMCA, Ararat, Victoria [distance: 841.022]
Prioritize within a circular region
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.
| parameter | value |
|---|---|
api_key |
get yours here |
text |
YMCA |
focus.point.lat |
-33.856680 |
focus.point.lon |
151.215281 |
boundary.circle.lat |
-33.856680 |
boundary.circle.lon |
151.215281 |
boundary.circle.radius |
50 |
Looking at these results, they are all less than 50 kilometers away from the focus point:
- YMCA, Redfern, New South Wales [distance: 3.836]
- YMCA, St Ives (NSW), New South Wales [distance: 14.844]
- YMCA, Epping (NSW), New South Wales [distance: 16.583]
- YMCA, Revesby, New South Wales [distance: 21.335]
- Caringbah YMCA, Caringbah, New South Wales [distance: 22.543]
- YMCA building, Loftus, New South Wales [distance: 25.756]
Filter your search
Pelias 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.
With Pelias, you can filter by:
sources: the originating source of the datalayers: the kind of place you want to find
Filter by data source
The search examples so far have returned a mix of results from all the data sources available to Pelias. Here are the sources being searched:
| source | name | short name |
|---|---|---|
| OpenStreetMap | openstreetmap |
osm |
| OpenAddresses | openaddresses |
oa |
| Who's on First | whosonfirst |
wof |
| GeoNames | geonames |
gn |
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.
| parameter | value |
|---|---|
api_key |
get yours here |
text |
YMCA |
sources |
oa |
Because OpenAddresses is, as the name suggests, only address data, here's what you can expect to find:
- 0 Ymca, New Brunswick
- 0 Ymca Drive, Cary, NC
- 14843 Ymca Lane, Cormorant, MN
- 14660 Ymca Lane, Cormorant, MN
- 6221 Ymca Lane, Northampton County, VA
- 6223 Ymca Lane, Northampton County, VA
- 74 Ymca Road, Wairoa District, Hawke's Bay Region
- 108 Ymca Drive, Clinton, SC
- 101 Ymca Drive, Kannapolis, NC
- 31440 Ymca Road, Washington, OH
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.
/v1/search?api_key=your-mapzen-api-key&text=YMCA&sources=osm,gn
| parameter | value |
|---|---|
api_key |
get yours here |
text |
YMCA |
sources |
osm,gn |
Each of these data sources has properties, licenses, and strengths. You can learn more about the data sources for Pelias.
Filter by data type
In Pelias, place types are referred to as layers, ranging from fine to coarse. The Pelias layers are derived from the hierarchy created by the gazetteer Who's on First and can be used to help coarse geocoding. Here's a list of the types of places you could find in the results, sorted by granularity:
| layer | description |
|---|---|
venue |
points of interest, businesses, things with walls |
address |
places with a street address |
street |
streets,roads,highways |
neighbourhood |
social communities, neighbourhoods |
borough |
a local administrative boundary, currently only used for New York City |
localadmin |
local administrative boundaries |
locality |
towns, hamlets, cities |
county |
official governmental area; usually bigger than a locality, almost always smaller than a region |
macrocounty |
a related group of counties. Mostly in Europe. |
region |
states and provinces |
macroregion |
a related group of regions. Mostly in Europe |
country |
places that issue passports, nations, nation-states |
coarse |
alias for simultaneously using all administrative layers (everything except venue and address) |
/v1/search?api_key=your-mapzen-api-key&text=YMCA&layers=venue,address
| parameter | value |
|---|---|
api_key |
get yours here |
text |
YMCA |
layers |
venue,address |
Available search parameters
| Parameter | Type | Required | Default | Example |
|---|---|---|---|---|
api_key |
string | yes | none | get yours here |
text |
string | yes | none | Union Square |
focus.point.lat |
floating point number | no | none | 48.581755 |
focus.point.lon |
floating point number | no | none | 7.745843 |
boundary.rect.min_lon |
floating point number | no | none | 139.2794 |
boundary.rect.max_lon |
floating point number | no | none | 140.1471 |
boundary.rect.min_lat |
floating point number | no | none | 35.53308 |
boundary.rect.max_lat |
floating point number | no | none | 35.81346 |
boundary.circle.lat |
floating point number | no | none | 43.818156 |
boundary.circle.lon |
floating point number | no | none | -79.186484 |
boundary.circle.radius |
floating point number | no | 50 | 35 |
sources |
string | no | all sources: osm,oa,gn,wof | openstreetmap,wof |
layers |
string | no | all layers: address,venue,neighbourhood,locality,borough,localadmin,county,macrocounty,region,macroregion,country,coarse | address,venue |
boundary.country |
string | no | none | 'GBR' |
size |
integer | no | 10 | 20 |