GIS Function

Which function is used to create a geospatial object from latitude and longitude values?

• ST_DWithin
  

• ST_Intersects

• ST_GeogPoint

• ST_Contains

Answer explanation

ST_GeogPoint(longitude, latitude): This function takes longitude and latitude values as input and constructs a GEOGRAPHY point object. This object represents a specific location on the Earth's surface.

What does the function ST_DWithin do?

• Creates a geospatial object

• Determines the relative location of two points or objects within a specified distance

• Renders GIS data with minimal configuration

• Converts JSON format to a geospatial object

Answer explanation

The ST_DWithin function is a spatial predicate in BigQuery that determines whether two geographic points or objects are within a specified distance of each other. It takes three arguments:

1. 1. The first geometry object (typically a point or polygon).
   

2. 2. The second geometry object (typically a point or polygon).
   

3. 3. The maximum distance in meters.
   

It returns TRUE if the two geometries are within the specified distance and FALSE otherwise.

Which format can be used with ST_GeogFromGeoJSON to generate a geospatial object?

• XML

• CSV

• JSON

• SQL

Answer explanation

ST_GeogFromGeoJSON(geojson_string): This function takes a string in GeoJSON format as input and returns a GEOGRAPHY object. GeoJSON is a standard format for encoding geographic data structures.

What is the purpose of the BigQuery Geo Viz application?

• To create SQL queries

• To render GIS data with minimal configuration

• To manage BigQuery datasets

• To perform machine learning tasks

Which additional geospatial functions can be used to overlay information on a map?

• ST_GeogPoint and ST_DWithin

• ST_MakeLine and ST_MakePolygon

• ST_Intersects and ST_Contains

• ST_Contains and ST_CoveredBy

Answer explanation

• ST_Intersects: This function checks if two geometries share any points in common. This is useful for determining if a point lies within a polygon (e.g., is a store located within a city boundary?) or if two polygons overlap (e.g., do two administrative regions share a border?).
  

• ST_Contains: This function checks if one geometry completely contains another. This can be used to identify points that are fully within a polygon (e.g., are all customers within a service area?) or to see if a polygon is entirely within another (e.g., is a neighborhood completely within a city?).

What does ST_GeogPoint do?

• Determines the relative location of two points

• Creates a geospatial object in well-known text (WKT) from values provided within the database

• Renders GIS data with minimal configuration

• Converts JSON format to a geospatial object

Answer explanation

ST_GeogPoint(longitude, latitude): This function takes two numerical arguments representing longitude and latitude, and creates a GEOGRAPHY object in Well-Known Text (WKT) format. This GEOGRAPHY object represents a specific point location on Earth.

Which functions allow reporting on the overlay or co-location of geospatial objects?

• ST_GeogPoint, ST_MakeLine, ST_MakePolygon

• ST_Intersects, ST_Contains, ST_CoveredBy

• ST_DWithin, ST_Intersects, ST_Contains

• ST_GeogFromGeoJSON, ST_Intersects, ST_CoveredBy

Answer explanation

• ST_DWithin: This function checks if two geometries are within a specified distance of each other. It's useful for finding points within a certain radius of a location or objects near each other.

• ST_Intersects: This function tests if two geometries share any points in common. This can be used to determine if a point is inside a polygon (e.g., a store within a city) or if two polygons overlap.
  

• ST_Contains: This function checks if one geometry completely contains another. This is helpful for finding points entirely within a polygon or polygons completely within another polygon.

What is the significance of using latitude and longitude in geospatial functions in BigQuery?

• They help create SQL queries

• They provide coordinates to create geospatial objects

• They are used for machine learning tasks

• They help manage BigQuery datasets