ARLAS Exploration API

The ARLAS API makes the ARLAS catalog available for exploration and browsing. The catalog contains collections of geo-referenced elements. Every element has a geometry, a centroid, a timestamp and a set of fields specific to the collection.

URL Schema

The table below lists the URL endpoints and their optional "parts". A part is composed of optional parameters. The parameters are separated with the character &.

PATH Template Description
/arlas/explore/_list List the collections configured in ARLAS
/arlas/explore/{collection}/_describe?form Describes the structure and the content of the given collection
/arlas/explore/{collection}/_count?filter & form Counts the number of elements found in the collection, given the filters
/arlas/explore/{collection}/_compute?compute & filter & form Computes the metric of a field in the collection, given the filters
/arlas/explore/{collection}/_search?filter & form & projection & page & returned_geometries Search and return the elements found in the collection, given the filters
/arlas/explore/{collection}/_geosearch?filter & form & projection & page & returned_geometries Search and return the elements found in the collection as features, given the filters
/arlas/explore/{collection}/_geosearch/{z}/{x}/{y}?filter & form & projection & page & returned_geometries Search and return the elements found in the collection and localized in the given tile(x,y,z) as features, given the filters
/arlas/explore/{collections}/_aggregate?aggregation &filter & form Aggregate the elements in the collection(s), given the filters and the aggregation parameters
/arlas/explore/{collections}/_geoaggregate?aggregation &filter & form Aggregate the elements in the collection(s) as features, given the filters and the aggregation parameters
/arlas/explore/{collections}/_geoaggregate/{geohash}?aggregation &filter & form Aggregate the elements in the collection(s) and localized in the given {geohash} as features, given the filters and the aggregation parameters
/arlas/explore/{collections}/_geoaggregate/{z}/{x}/{y}?aggregation &filter & form Aggregate the elements in the collection(s) and localized in the given zxy tile as features, given the filters and the aggregation parameters
/arlas/explore/{collections}/_suggest?filter & form & size & suggest Suggest the the n (n=size) most relevant terms given the filters

When multiple collections are permitted ({collections}), the comma is used for separating the collection names.

Examples
https://api.gisaia.com/demo/arlas/explore/_describe
https://api.gisaia.com/demo/arlas/explore/city,state,country/_describe
https://api.gisaia.com/demo/arlas/explore/city,state,country/_count?q=bord*&f=country:France&pretty=true
https://api.gisaia.com/demo/arlas/explore/election/_search?f=country:France&f=$timestamp:range:[0<1490613808000]&pretty=true&size=1000&include=id,name
https://api.gisaia.com/demo/arlas/explore/election/_aggregate?f=country:France&f=$timestamp:range:[0<1490613808000]&pretty=true&size=1000&include=id,name&agg=geohash&agg_interval=4

All URLs are accessible both with GET and POST requests. For POST requests, URL parts are passed as a JSON representation.

URL Parts

Part: aggregation

The [aggregation] url part allows the following parameters to be specified:

Parameter Default value Description Multiple
agg None Gathers a set of sub-parameters indicating the type of aggregation, the field used as the aggregation key and possibly the interval for numeric values true for _aggregate only

The agg parameter should be given in the following format :

  • {type}:{field}:interval-{interval}:format-{format}:collect_field-{collect_field}:collect_fct-{function}:order-{order}:on-{on}:size-{size}

Where the {type}:{field} part is mandatory

The other parts must be specified or not depending on the aggregation type. All the cases are sum up in the following table.

Parameter Aggregation type Description
interval datehistogram, histogram, geohash, geotile mandatory
format datehistogram optional (default value : yyyy-MM-dd-HH:mm:ss)
(collect_field,collect_fct) All types optional and multiple
(order,on) term, histogram, datehistogram optional
size term, geohash, geotile optional
include term optional
aggregated_geometries All types optional
raw_geometries All types optional
fetch_hits All types optional

Example: agg=datehistogram:date:interval-20day:format-dd.MM.yyyy&agg=term:sexe:collect_field-age:collect_fct-avg:order-asc:on-result:size-5

The sub-parameters possible values are:

Parameter Values Description
{type} datehistogram, histogram, geohash, geotile, term Type of aggregation
{field} {field} Aggregates on {field}
interval {interval} Size of the intervals.(1)
format Date format for key aggregation Date format for key aggregation.
collect_field {collect_field} The field used to aggregate collections.
collect_fct avg,cardinality,max,min,sum,geobbox,geocentroid (2) The aggregation function to apply to collections on the specified collect_field.
order asc,desc Sorts the aggregation buckets on the field name, on the count of the buckets or on the the result of a metric sub-aggregation, ascending or descending.
on field,count,result (3) (3') {on} is set to specify whether the order is on the field name, on the count of the aggregation or the result of a metric subaggregation.
size {size} Defines how many buckets should be returned.
include Comma separated strings (4) Specifies the values for which buckets will be created.
aggregated_geometries Comma separated strings : bbox, centroid, tile_center, tile Allows to specify a list of aggregated forms of geometries that represent the bucket (5)(6)
raw_geometries {geo_field1}(+{field1}, ...);{geo_field2}(-{field2}, ...) Allows to specify a list of raw geometries provided by hits that represent the bucket and that are elected by a sort (7)(8)
fetch_hits {optionalNumberOfHist}(+{field1}, {field2}, -{field3}, ...) Specifies the number of hits to retrieve inside each aggregation bucket and which fields to include in the hits. The hits can be sorted according 0-* fields by preceding the field name by + for ascending sort, - for descending sort or nothing if no sort is desired on a field.(9)

(1) Each aggregation type ({type}) has its own type of interval. The table below lists the semantic of the interval sub-parameter.

(2) (collect_field,collect_fct) should both be specified. It's possible to apply multiple metric aggregations by defining multiple (collect_field,collect_fct) couples. They should be unique in that case. The metrics geobbox and geocentroid are returned as features collections.

(3) When on is result, then (collect_field,collect_fct) should be specified. Except when collect_fct = geobbox or geocentroid, then on=result is prohibited .

(3') If on is equal to result and two or more (collect_field,collect_fct) couples are specified, then the order is applied on the first collect_fct different from geobbox and geobbox".

Example: agg=term:sexe:collect_field-location:collect_fct-geobbox:collect_field-age:collect_fct-avg:collect_field-height:collect_fct-max:order-asc:on-result

The order is applied on the first collect_fct avg (that is different from geobbox).

(4) If one value is specified then regular expressions can be used (only in this case) and buckets matching them will be created. If more than one value are specified then only buckets matching the exact values will be created.

(5) Available aggregated geometries :

  • bbox: returns the data extent (bbox) inside the bucket.
  • centroid: returns the centroid of data inside the bucket.
  • tile: returns the tile extent (zxy or geohash) of each bucket. This form is supported for geohash and geotile aggregation type only.
  • tile_center: returns the 'center' of the tile extent that represents the bucket. This form is supported for geohash and geotile aggregation type only.

(6) The response:

  • For _aggregate service: the aggregated geometries are returned in geometries list in the json response. Each object inside this list has : the reference to the aggregated form, the geojson geometry and an attribute is_raw set to false.
  • For _geoaggregate service: each bucket of the aggregation will be represented with as many features (in a feature collection) as there are specified aggregated geometries. The properties of each feature has :
    • geometry_ref attribute that informs which aggregated form is returned.
    • geometry_type attribute set to aggregated.

(7) Any field of the collection whose type is geo-point or geo-shape can be set in raw_geometries.

  • Sort fields are optional. If no sort is specified, an ascending sort on collection.params.timestamp_path is applied.
  • A sort field can be preceded by '-' for descending sort. Otherwise the sort is ascending

(8) The response :

  • For _aggregate service: the aggregated geometries are returned in geometries list in the json response. Each object inside this list has : the reference to the geometry path, the used sort, the geojson geometry and an attribute is_raw set to true.
  • For _geoaggregate service: each bucket of the aggregation will be represented with as many features (in a feature collection) as there are specified raw geometries. The properties of each feature has :
    • geometry_ref attribute that informs which geometry path is returned.
    • geometry_type attribute set to raw.
    • geometry_sort attribute that informs how the geometry path is fetched (with what sort).
    • Example: raw_geometries-geo_field1,geo_field2 || raw_geometries-geo_field(-field1,field2) || raw_geometries-geo_field1(field1);geo_field2(field2,field3) (9)

  • Example: fetch_hits-3(-timestamp, geometry). The 3 last positions are retrieved for each bucket

Note that if the number of hits to fetch is not specified, 1 is considered as default.

  • Example: fetch_hits:(-timestamp, geometry). The last position is retrieved for each bucket

Service Aggregation type Interval Description
_aggregate datehistogram {size}(year,quarter,month,week,day,hour,minute,second) Size of a time interval with the given unit (no space between number and unit). Size must be equal to 1 for year, quarter, month and week
_geoaggregate geohash {length} The geohash length: lower the length, greater is the surface of aggregation. See table below.
_geoaggregate geotile {zoom} The tile zoom: lower the zoom, greater is the surface of aggregation.
_aggregate histogram {size} The interval size of the numeric aggregation
_aggregate term None None

The table below shows the metric dimensions for cells covered by various string lengths of geohash. Cell dimensions vary with latitude and so the table is for the worst-case scenario at the equator.

GeoHash length Area width x height
1 5,009.4km x 4,992.6km
2 1,252.3km x 624.1km
3 156.5km x 156km
4 39.1km x 19.5km
5 4.9km x 4.9km
6 1.2km x 609.4m
7 152.9m x 152.4m
8 38.2m x 19m
9 4.8m x 4.8m
10 1.2m x 59.5cm
11 14.9cm x 14.9cm
12 3.7cm x 1.9cm

agg parameter is multiple. Every agg parameter specified is a subaggregation of the previous one : the order matters.

For _geoaggregate service, the first (main) aggregation must be geohash,or geotile.


Part: filter

Available filter parameters

The filter url part allows the following parameters to be specified:

Parameter Default value Values Description Multiple
f None {fieldName}{operator}{value} A triplet for filtering the result. Multiple filter can be provided. The order does not matter. A triplet is composed of a field name, a comparison operator and a value. The AND operator is applied between filters. For the :eq: and :range: filters, values can be comma separated (field:eq:v1,v2) which stands for an OR. For the :ne: filter, values can be comma separated (field:ne:v1,v2) which stands for an AND true
q None {text} or {fieldname}:{text} A full text search. Optionally, it's possible to search the text on a specific field false
dateformat None Joda time pattern A date format pattern that respects the Joda-time syntax false

Important

The given BBOX must respect the following rules : - west and east must be between -180 and 180 inclusive - west must be different from east (west=east is invalid) - You can specify west>east which means the bbox crosses the dateline - south and north must be between -90 and 90 inclusive and south<north

Important

For parameters that accept WKT, in case of a Polygon or MultiPolygon, the orientation should be clock-wise (right). Otherwise, ARLAS-server will attempt to parse it as the "Complementary" Polygon on the other facet of the planet. For instance the polygon POLYGON ((-170 -10, -175 10, 175 10, 170 -10, -170 -10)) is counter clock-wise. If it's passed as a parameter, ARLAS-server will interpret it as the Polygon that crosses the dateline POLYGON ((-170 -10, -175 10, 185 10, 180 -10, -170 -10)) which is clock-wise.

Important

Coordinates of the given WKT must be contained in the Envelope -360, 360, -180, 180

Filter parameters algebra

For each parameter, you can provide multiple filters. There are 2 different ways to do this : - in distinct filter parameters = AND operator between filters - in the same filter parameter as a semi-colon separated list = OR operator between filters

Multiple type Example Operator Result
Distinct filter parameters f=age:gte:18&f=age:lte:60 AND elements whose/which age between 18 and 60
Same filter parameter f=age:gte:18;age:lte:60 OR elements with any age

Of course, you can combine both way to handle complex multiple filters for each filter parameter type.

f parameter syntax

Operator Description Value type
:eq: {fieldName} equals {comma separated values}. OR operation is applied for the specified values numeric or strings
:ne: {fieldName} must not equal {comma separated values }. AND operation is applied for the specified values numeric or strings
:like: {fieldName} is like {value}. numeric or strings
:gte: {fieldName} is greater than or equal to {value} numeric
:gt: {fieldName} is greater than {value} numeric
:lte: {fieldName} is less than or equal to {value} numeric
:lt: {fieldName} is less than {value} numeric
:range: {fieldName} is between {comma separated [min<max] values}. OR operation is applied for the specified ranges numeric or strings. If the field's type is date, min & max should be timestamps in millisecond or Date expression Note that dates in date expressions can either be now or timestamp in millisecond. Other date formats are not supported.
:within: {GeofieldName} is within the {given WKT string or the given BBOX : west, south, east, north}. a WKT string or the BBOX string : "west, south, east, north"
:notwithin: {GeofieldName} is not within the {given WKT string or the given BBOX : west, south, east, north}. a WKT string or the BBOX string : "west, south, east, north"
:intersects: {GeofieldName} intersects the {given WKT string or the given BBOX : west, south, east, north}. a WKT string or the BBOX string : "west, south, east, north"
:notintersects: {GeofieldName} does not intersect the {given WKT string or the given BBOX : west, south, east, north}. a WKT string or the BBOX string : "west, south, east, north"

The :range: operator has a specific syntax to indicates if range bounds are taken into account or not.

Range operator syntax Meaning
x:range:]min<max[ min<x<max
x:range:[min<max] min<=x<=max
x:range:]min<max] min<x<=max
x:range:[min<max[ min<=x<max
x:range:]min1<max1[,]min2<max2[ min1<x<max1 OR min2<x<max2

On top of that, :range: operator supports generic aliases to represent collection configured fields : * $timestamp refers to collection's timestamp field.

Example: f=city:eq:Toulouse&f=city:eq:Bordeaux&f=$timestamp:range:[0<1490613808000]

Special syntax for date queries using lt, gt, lte, gte and range operations

In the case of lt, gt, lte, gte, range operations that are applied on date fields, the date values have four possible forms :

  • a timestamp in millisecond OR a date in a custom format(*).
  • a timestamp in millisecond OR a date in a custom format(*) followed by || and followed by a date operation (+1h, /M, -2y, ...)
  • now
  • now followed by a date operation (+1h, /M, -2y, ...)

Note

(*) If a custom format is given in the query, then the dateformat parameter must be set.

Note

The dateformat parameter must not contain ||.

Note

The dateformat parameter can be set only if a date field is queried in f param; when using gt, lt, gte, lte and range operations.

Note

Some examples of dates operations :

  • +1h : adds one hour

  • -1M : substracts one month

  • /d : rounds up or down to the nearest day

The date is rounded up when using lte and gt and rounded down when using lt and gte

A date operation can be the concatenation of an add/substract operation and a round operation : i.e now-1M/d

The date expression: timestamp:gte:now-1M/M substracts 1 month from now then the resulted date is rounded down to the beginning of the month. Assuming now is 2018-06-15. timestamp:gte:now-1M/M is equivalent to timestamp:gte:2016-05-01

Partition filtering

filter part can also be passed in request header partition-filter as a serialized json for partitioning concerns.

Example: curl --header "partition-filter: {f":[[{"field":"city","op":"eq","value":"Bordeaux"}]]}" https://api.gisaia.com/demo/arlas/explore/cities/count

Column filtering

A coma-separated list of columns can be passed in request header column-filter. Wildcards are supported.

A column filter stands for the fields that are available to a request body:

  • if a request body field doesn't belong to the column filter, a 403 is returned with the message The field '%s' isn't available or The fields '%s' aren't available;
  • only fields that belong to the column filter can be returned.

A column filter can be related to a collection, e.g. mycollection:myfield or it can be related to every collection, e.g. myfield. Trying to access a collection with no available field returns a 403. Collection names can be omitted or end with a '*'.

Examples of column-filter:

  • mycollection:params.city,mycollection:params.country makes available params.city and params.country for collection mycollection
  • mycollection*:params.city makes available params.city for all collections whose names start with mycollection
  • params, params*, params.*, *params make available params.city, params.country, params.weight, and so on. for every collection
  • params, :params, *:params make available params and subfields for every collection
  • * makes all fields available
  • *.* makes only subfields available, e.g. params.city and params.country but not id

If no column filter, or a blank column filter is provided, then no filtering is done.

The following endpoints use this header:

Endpoint Filtering result
/arlas/explore/_list Only fields and collections matching this filter will be returned (if no field of a collection is available, this one is not returned at all).
/arlas/explore/{collection}/_describe Only fields matching this filter will be returned. Return a 403 if target collection is not available.
/arlas/explore/{collection}/_count Return a 403 if one of the filter fields is not in the column filter. Return a 403 if target collection is not available.
/arlas/explore/{collection}/_compute Return a 403 if the field, or one of the filter fields, is not in the column filter. Return a 403 if target collection is not available.
/arlas/explore/{collection}/_search Return a 403 if one of the filter, projection and page fields is not in the column filter. Otherwise only fields matching the filter will be returned. Return a 403 if target collection is not available.
/arlas/explore/{collection}/_geosearch Return a 403 if one of the filter, projection or page fields is not in the column filter. Otherwise only fields matching the filter will be returned. Return a 403 if target collection is not available.
/arlas/explore/{collection}/_geosearch/{z}/{x}/{y} Return a 403 if one of the filter, projection or page fields is not in the column filter. Otherwise only fields matching the filter will be returned. Return a 403 if target collection is not available.
/arlas/explore/{collections}/_aggregate Return a 403 if one of the aggregation or filter fields is not in the column filter. Return a 403 if target collection is not available.
/arlas/explore/{collections}/_tile/{z}/{x}/{y}.png Return a 403 if one of the filter, projection or page fields is not in the column filter. Return a 403 if target collection is not available.
/arlas/explore/{collections}/_geoaggregate Return a 403 if one of the aggregation or filter fields is not in the column filter. Return a 403 if target collection is not available.
/arlas/explore/{collections}/_geoaggregate/{geohash} Return a 403 if one of the aggregation or filter fields is not in the column filter. Return a 403 if target collection is not available.
/arlas/explore/{collections}/_geoaggregate/{z}/{x}/{y} Return a 403 if one of the aggregation or filter fields is not in the column filter. Return a 403 if target collection is not available.
/arlas/explore/ogc/opensearch/{collection} Only fields matching this filter will be returned. Return a 403 if target collection is not available.

On top of that, a query ("q" parameter) filter MUST target a specific field:

  • fullname:john is valid
  • john isn't valid and will return a 403
  • params*:john isn't valid neither and will return a 403

If a projection with an includes parameter is used, then:

  • included fields that are wildcards aren't checked; they do not return a 403 if they don't match the column filter;
  • and only included fields that match the column filter are returned

Part: form

The form url part allows the following parameters to be specified:

Parameter Default value Values Description Multiple
pretty false true,false Pretty print false
flat false true,false Flats the data property map false

Example: pretty=true&flat=false


Part: field

The compute url part is used in _compute service.

Parameter Default value Values Description Multiple
field false true,false The field on which the metric is calculated false
metric `` max, min, avg, sum, cardinality, spanning, geobbox, geocentroid The metric to compute false

!!! note 'Note' - max : the maximum value of the given field. Field should be numeric or date. - min : the minimum value of the given field. Field should be numeric or date. - avg : the average of the given field values. Field should be numeric or date. - sum : the sum of the given field values. Field should be numeric or date. - cardinality : the number of distinct values of the given field. - spanning : the range value (max-min) of the given field. Field should be numeric or date. - geobbox : the extend of data based on the given geo-point field. - geocentroid : the centroid of data based on the given geo-point field.

!!! info '_range endpoint is removed' Starting from v13.7.0, _range endpoint is removed. You can use the endpoint _compute instead. - If you used _range to get the (max-min) value of the given field, then you can call : _compute?field=your_field&metric=spanning - If you used _range to get separately the min and max values of the given field, then you can call _compute twice using _compute?field=your_field&metric=min and _compute?field=your_field&metric=max

Example: field=timestamp


Part: projection

The projection url part allows the following parameters to be specified:

Parameter Default value Values Description Multiple
include * {fieldNamePattern} List the name patterns of the field to be included in the result. Seperate patterns with a comma. true
exclude * {fieldNamePattern} List the name patterns of the field to be excluded in the result. Seperate patterns with a comma. true

Example: include=*&exclude=city,state


Part: returned_geometries

The returned_geometries url part can be specified in _search & _geosearch services:

Parameter Default value Values Description Multiple
returned_geometries {Comma separated geofieldNamePattern} Comma separated geometry field_paths to be included in the result. If not specified, only geometry_path is returned. If geometry_path is null, then centroid_path is returned false

Example: include=*&exclude=city,state


Part: suggest

The suggest url part allows the following parameters to be specified:

Parameter Default value Values Description Multiple
field _all {fieldName} Name of the field to be used for retrieving the most relevant terms false

Example: field=recommended


Part: page

The page url part allows the following parameters to be specified:

Parameter Default value Values Description Multiple
size 10 > 0 The maximum number of entries or sub-entries to be returned. false
from 0 > 0 An offset to start the search from. Defaults to 0. false
sort None ((-?)({field} OR geodistance:{lat} {lon}))(,(-?){field})* Sorts the resulted hits on the given fields and/or by distance to a given point false (separate fields with comma in the same parameter)
after None {value1},{value2},... List of values of fields present in sort param that are used to get the following hits of a previous search false (separate values with comma in the same parameter)
before None {value1},{value2},... List of values of fields present in sort param that are used to get the precedent hits of a previous search false (separate values with comma in the same parameter)

sort parameter

Syntax

sort=((-?)({field} OR geodistance:{lat} {lon}))(,(-?){field})*.

Notes

  • {field} can be preceded by '-' for descending sort. By default, sort is ascending.
  • The order of fields matters.

Tip : geodistance sort

Along with the comma separated fields, you can add geodistance:{lat} {lon} (at most 1 time) to sort the hits centroids by distance to the given {lat} {lon} (ascending sort).

Example 1

sort=age,-timestamp. Resulted hits are sorted by age. For same age hits, they are decreasingly sorted in time.

Example 2

sort=age,geodistance:89 179. Resulted hits are sorted by age. For same age hits, they are sorted by the closest distance to the point (89°,179°).

after and before parameter

Important

after and before parameter work only combined with sort parameter.

Syntax

after={value1},{value2},...,{valueN} & sort={field1},{field2},...,{fieldN}

Notes

  • {value1} and {value2} are the values of {field1} and {field2} in the last hit returned in the previous search.
  • The last field {fieldN} must be the id field specified in the collection collection.params.idPath (returned as md.id) and {valueN} its corresponding value.
  • from parameter must be set to 0 or kept unset

The difference between after and from

  • after is used to scroll over the fetched hits.
  • from is more an offset from which fetching hits starts and is not exclusively used for scrolling (scrolling is possible by combining from and size parameters).

Example

sort=-date,id & after=01/02/2019,abcd1234. Gets the following hits of the previous search that stopped at date 01/02/2019 and id abcd1234.


OpenSearch

If enabled, ARLAS offers an Opensearch Description document (/arlas/ogc/opensearch/{collection}).