Overview

Types

Surface generation is the foundation of all the advanced features of the Airspace Link API. It has its own
set of types and lexicon that assist in making the queries intuitive and powerful.

Layer Object

The layer object represents the building block for requesting surface information. At a minimum, provide a code and
that data source will be fetched. You can access attributes using the JSON key fields, and you can
provide a filter using the JSON key where.

Parameter	Type	Description
`code`	string	A `metadata` source.
`fields`	string[]	The fields of the metadata source you'd like to return. Setting `"fields": ["*"]` will return all valid fields for supported data types.
`where`	`<where>`	A pseudo-SQL expression tree. Click here for information on how to generate one.
`risk`	float64	An optional risk value to assign to the layer. Only relevant when requesting risk surfaces.

SQL Expression Tree

Backus-Naur Form

Simple comparisons

Logical operators

Several API endpoints require generating surfaces, and all surface generation supports advanced querying.
You can provide a filter via a tree data structure for each resource you request that will be parsed out
and produce a filter that suits your use case.

Logical operators

Operator	Arity	Description
`AND`	Binary or greater	A standard logical `AND`. All the arguments provided to the `AND` will be nested.
`OR`	Binary or greater	A standard logical `OR`. All the arguments provided to the `OR` will be nested.

Comparison operators

Operator	Arity	Description
`=`	Binary	`=` does an equality check on the field and the passed value. Type coercion may be performed if the types are different.
`>`	Binary	`>` checks the field is greater than the passed value. Type coercion may be performed if the types are different.
`<`	Binary	`<` checks the field is less than the passed value. Type coercion may be performed if the types are different.
`<=`	Binary	`<=` checks the field is less than or equal to the passed value. Type coercion may be performed if the types are different.
`>=`	Binary	`>=` checks the field is greater than or equal to the passed value. Type coercion may be performed if the types are different.
`!=`	Binary	`!=` checks the field is not equal to the passed value. Type coercion may be performed if the types are different.

Types#

Layer Object#

SQL Expression Tree#

Types

Layer Object

SQL Expression Tree