
Configure geospatial lookups
You use geospatial lookups to create queries that return results that Splunk software can use to generate a choropleth map visualization. Choropleth maps cannot be rendered without the data generated by corresponding geospatial lookups.
A geospatial lookup matches location coordinates in your events to location coordinate ranges in a geographic feature collection (a KMZ, or Keyhole Markup Language, file) and outputs fields to your events that provide corresponding geographic feature information that is encoded in the feature collection. This geographic information usually represents a geographic region that can share borders with geographic regions of the same type, like a country, state, province, or county.
Splunk provides two geospatial lookups for the United States and for world countries, enabling you to render choropleth maps of:
- The USA, divided up into state regions.
- The world, divided up into countries.
This topic shows you how to create additional geospatial lookups that break up choropleth maps into other types of regions (counties, provinces, timezones, and so on).
For more information about choropleth maps and geographic data visualizations, see Mapping data, in the Dashboards and Visualizations manual.
The FeatureId and featureCollection fields
Geospatial lookups differ from other lookup types in that they are designed to always output these two fields: featureId
and featureCollection
. The featureId
is the "name" of the feature, like "California" or "CA" or whatever is encoded in the feature collection. The featureCollection
field provides the name of the lookup in which the feature was found.
If you pipe the output of a geospatial lookup directly into a geom
command, the command does not need to be given the lookup name. The geom
command detects the featureId
and featureCollection
fields in the event and uses the lookup to generate the geographic data structures that the Splunk software requires to generate a choropleth map. However, be aware that geographic data structures can be large; so much so that it is strongly discouraged to pipe events into the geom command, as geographic data structures will be attached to every event. Instead, you should first perform stats on the results of your geographic lookup, and only perform geom on a "boiled down" aggregated statistic like count by featureId.
Define a geospatial lookup stanza in transforms.conf
The geospatial lookup stanza provides the location of the geographic feature collection that is to be used as a lookup table. It can optionally include:
- a
feature_id_element
attribute. - field matching rules.
- rules for time-bounded lookups.
See "The geospatial lookup stanza format" for details.
If you want a geospatial lookup to be available globally, add its lookup stanza to the version of transforms.conf
in $SPLUNK_HOME/etc/system/local/
. If you want the lookup to be specific to a particular app, add its stanza to the version of transforms.conf
in $SPLUNK_HOME/etc/apps/<app_name>/local/
.
Caution: Do not edit configuration files in $SPLUNK_HOME/etc/system/default
.
The geospatial lookup stanza format
When you add a geospatial lookup stanza to transforms.conf
it should follow this format.
[<lookup_name>] external_type = geo filename = <name_of_KMZ_file> feature_id_element = <XPath_expression>
[<lookup_name>]
is the name of the lookup.external_type
should be set togeo
if you are defining a geospatial lookup.filename
is the name of the KMZ file that you are using. KMZ files are also referred to as "geographic feature collections."- Two feature collections are provided:
geo_us_states
for the United States, andgeo_countries
for the countries of the world. - You can optionally upload geographic feature collections for other regions and feature types, such as US counties or European provinces.
- Two feature collections are provided:
feature_id_element
is an optional attribute. It is an XPath expression that defines a path from a Polygon element in the KML file to some other XML element or attribute that contains the name of the feature. This is needed in cases where the typical style of named Placemark element is not in use.feature_id_element
may be required in cases where thefeatureID
field generated by the lookup is an empty string, or when the feature collection returns incorrect features by default. In the latter case the feature that you want may be a peer of the default feature or is located relative to the default feature.- To determine what path you need, study the geographic feature collection. Each feature in the collection is tagged with
Placemark
, and eachPlacemark
contains aname
that the lookup writes out asfeatureId
fields. - The default setting for
feature_id_element
is/Placemark/name
.
Configure a geospatial lookup
Prerequisities
- See about lookups and field actions for more information on lookups.
- See Add field matching rules to your lookup configuration for information on field/value matching rules.
- See Make your lookup automatic for information on configuring an automatic lookup.
Steps
- (Optional) Upload a geographic feature collection to your Splunk deployment, if you need to use a collection other than
geo_us_states
orgeo_countries
.- Geographic feature collections are encoded as KMZ (Keyhole Markup Language) files.
- Upload the feature collection in Settings. Navigate to Settings > Lookups > Lookup table files.
- If you have a KML file, you can convert it to a KMZ file by compressing it and replacing the
.zip
extension with.kmz
.
- Create a geospatial lookup stanza in
transforms.conf
, following the stanza format described in The geospatial lookup stanza format above.- If you want the lookup to be available globally, add its lookup stanza to the version of
transforms.conf
in$SPLUNK_HOME/etc/system/local/
. If you want the lookup to be specific to a particular app, add its stanza to the version oftransforms.conf
in$SPLUNK_HOME/etc/apps/<app_name>/local/
.
- Caution: Do not edit configuration files in
$SPLUNK_HOME/etc/system/default
.
- If you want the lookup to be available globally, add its lookup stanza to the version of
- (Optional) Set up field/value matching rules for the geospatial lookup.
- (Optional) Make the geospatial lookup an automatic lookup by adding a configuration to
props.conf
.- If you want the automatic lookup to be available globally, add its lookup stanza to the version of
props.conf
in$SPLUNK_HOME/etc/system/local/
. If you want the lookup to be specific to a particular app, add its stanza to the version ofprops.conf
in$SPLUNK_HOME/etc/apps/<app_name>/local/
.
- Caution: Do not edit configuration files in
$SPLUNK_HOME/etc/system/default
.
- If you want the automatic lookup to be available globally, add its lookup stanza to the version of
- Save your
.conf
file changes. - Restart Splunk Enterprise to implement your changes.
- If you have set up an automatic lookup, after restart you should see the
output
fields from your lookup table listed in the fields sidebar. From there, you can select the fields to display in each of the matching search results.
- If you have set up an automatic lookup, after restart you should see the
Geospatial lookup example
Here is a geospatial lookup called geo_us_states
. It is located in $SPLUNK_HOME/etc/system/bin/
.
[geo_us_states] external_type=geo filename=geo_us_states.kmz
This lookup deals with a geographic feature collection that contains US states.
To use this lookup to build a choropleth map, you need to create a search that queries it in a manner that returns results that can be used to generate the map. The search needs to do all of these things:
- Indicate an events data source.
- Query the lookup by matching fields in your events to fields in the KMZ file.
- Include a transforming command that aggregates the data using
featureId
, the lookup's geographic output field. - Use the
geom
search command to generate data that can be used to create a choropleth map.
This is a partial choropleth map query. It meets the first two of the four requirements listed above for a choropleth map lookup search. It returns the latitude and longitude for features in the feature collection.
sourcetype=crime_data cc=USA | lookup geo_us_states latitude, longitude
The output of that lookup should look something like this:
_featureIdField | featureId | featureCollection | latitude | longitude |
---|---|---|---|---|
featureId | AK | geo_us_states | y | x |
featureId | AL | geo_us_states | y | x |
You can update this search to display results for the geom
command. Note that the geom
command should be preceded by a transforming command operation, such as this one involving count
.
This is a full choropleth map query. It retrieves crime event counts by US state and adds the geometry of each state as a geom
column.
sourcetype=crime_data cc=USA | lookup geo_us_states latitude, longitude | stats count by featureId | geom
The output of that search should look something like this:
_featureIdField | featureId | geom | count |
---|---|---|---|
featureId | AK | {...} | 10 |
featureId | AL | {...} | 15 |
_featureIdField
is a hidden field that works with the geomfilter
post-process search command, when you run a search that contains it. It allows geomfilter
to know which field contains the featureId
values, even when featureId
is renamed to something else.
For example, say you rename featureId
to state
. If you run geomfilter
, it consults the stored search results in the search dispatch folder and looks in the _featureIdField
column, where it finds the value state
. This causes it to seek the featureId
values it needs for its calculations in the state
column.
For more information about geospatial lookup search queries, see "Mapping data" in the Dashboards and Visualizations manual.
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This documentation applies to the following versions of Splunk® Enterprise: 6.5.7
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