Reverse geocoding and feature types

Adapted from https://developers.arcgis.com/rest/geocode/api-reference/geocoding-reverse-geocode.htm

Reverse geocode details

The purpose of reverse geocoding is to answer the question: What’s near this location? To answer this question, the reverseGeocode operation provided by the ArcGIS REST API returns the most relevant feature near an input location based on a prioritized hierarchy of feature types.

The hierarchy is summarized in the table below, ordered by descending priority. Unless otherwise noted, each feature type is only returned when the distance between the input location and the feature is within the tolerance specified in the Search Tolerance column.

Table 1: Adapted from ArcGIS REST API reverseGeocode

Feature type	Search tolerance	Comments
StreetInt	10 meters	Intersections are only returned when featuretypes = "StreetInt" is included in the request.
StreetAddress (near), DistanceMarker, or StreetName	3 meters	Candidates of type StreetName are only returned if featureTypes = "streetName" is included in the request.
POI centroid	25 meters	A business or landmark that can be represented by a point.
Subaddress	10 meters	Subaddress candidates, which can be features such as apartments or floors in a building, maybe not being returned under certain conditions.
PointAddress	50 meters	A PointAddress match is not returned if it is on the opposite side of the street as the input location, even if it is within 50 meters of the location.
StreetAddress (distant), DistanceMarker, or StreetName	100 meters	Candidates of type StreetName are only returned if featuretypes = "StreetName" is included in the request.
POI area	within boundary	A business or landmark that can be represented by an area, such as a large park or university. Not available in all countries.
Postal or Locality area	within boundary	If the input location intersects multiple boundaries, the feature with the smallest area is returned.

In arcgeocoder, this hierarchy is implemented in arc_reverse_geo(), specifically through the featuretypes parameter. The default value (featuretypes = NULL) does not include the parameter in the API call. In this case, the hierarchy presented in the previous table would apply.

It is possible to narrow down the output of the query to a specific feature type or a list of feature types.The possible values supported for this parameter are:

• "StreetInt"
• "DistanceMarker"
• "StreetAddress"
• "StreetName"
• "POI"
• "Subaddress"
• "PointAddress"
• "Postal"
• "Locality"

As mentioned, is to possible to include several feature types. If more than one value is specified for the parameter, the values must be separated by a comma, with no spaces after the comma.

single featuretypes value

arc_reverse_geo(..., featuretypes = "PointAddress")

multiple featuretypes value

arc_reverse_geo(..., featuretypes = c("PointAddress", "StreetAddress"))

Examples

In the following examples, we would provide different examples for better understanding.

library(arcgeocoder)
library(dplyr)

Example 1: Match to POI centroid returned

In this example, we do not provide any value to the featuretypes parameter. This input location is within the search tolerance of both POI and PointAddress features, but a match to the POI centroid is returned because it has a higher priority (see Table 1). Note that the output field Addr_type indicates the type of feature.

example_x <- -117.203741
example_y <- 40.95029

api_poi <- arc_reverse_geo(
  x = example_x, y = example_y,
  langcode = "EN", full_results = TRUE, verbose = TRUE
)

api_poi %>%
  select(x, y, address, lon, lat, Addr_type) %>%
  knitr::kable()

x	y	address	lon	lat	Addr_type
-117.2037	40.95029	89414, Golconda, NV, USA	-117.2037	40.95029	Postal

Example 2: Locality match returned

api_local <- arc_reverse_geo(
  x = example_x, y = example_y,
  featuretypes = "Locality",
  langcode = "EN", full_results = TRUE, verbose = TRUE
)

api_local %>%
  select(x, y, address, lon, lat, Addr_type) %>%
  knitr::kable()

x	y	address	lon	lat	Addr_type
-117.2037	40.95029	Humboldt County, NV, USA	-117.2037	40.95029	Locality

Example 3: multiple values

When multiple values are included in the API call, the hierarchy explained in Table 1 would still be applied on the requested featuretypes.

api_multiple <- arc_reverse_geo(
  x = example_x, y = example_y,
  featuretypes = c("Locality", "StreetInt", "StreetAddress"),
  langcode = "EN", full_results = TRUE, verbose = TRUE
)

api_multiple %>%
  select(x, y, address, lon, lat, Addr_type) %>%
  knitr::kable()

x	y	address	lon	lat	Addr_type
-117.2037	40.95029	Humboldt County, NV, USA	-117.2037	40.95029	Locality

Example 4: No results for specific featuretypes

In the following example we present a case where only certain featuretypes are near the requested location. In this case, when reverse geocoding the North Pole the API would return a Locality but no StreetAddress is found.

When it is not possible to return results, arc_reverse_geo() returns an empty tibble.

# North Pole

npole <- arc_reverse_geo(x = 0, y = 90, langcode = "EN", full_results = TRUE)

npole %>%
  select(x, y, address, lon, lat, Addr_type) %>%
  knitr::kable()

x	y	address	lon	lat	Addr_type
0	90	Ozero Shybyndy	0	90	POI

# But no StreetAddress
npole2 <- arc_reverse_geo(
  x = 0, y = 90, langcode = "EN", full_results = TRUE,
  featuretypes = "StreetAddress"
)

npole2 %>%
  knitr::kable()

x	y	address
0	90	NA

Conclusion

The API would return different results for the same x,y values depending on the value of featuretypes. By using featuretypes = NULL the feature type returned would depend on the hierarchy explained in Table 1.

Depending on the location, the featuretype filter may not return results, hence for general purposes using featuretypes = NULL is safer.