Filter geo-temporal data by region
- Define a geographic region
  - box
    - Example box-shaped region
- circle
  - Example circular region
polygon
- Example polygonal region
Strict and non-strict filtering
- Related

Filter geo-temporal data by region

Use the geo.filterRows function to filter geo-temporal data by geographic region:

Define a geographic region
Use strict or non-strict filtering

The following example uses the sample bird migration data and queries data points within 200km of Cairo, Egypt:

import "experimental/geo"
sampleGeoData
    |> geo.filterRows(region: {lat: 30.04, lon: 31.23, radius: 200.0}, strict: true)

Define a geographic region

Many functions in the Geo package filter data based on geographic region. Define a geographic region using one of the the following shapes:

box
circle
polygon

box

Define a box-shaped region by specifying a record containing the following properties:

minLat: minimum latitude in decimal degrees (WGS 84) (Float)
maxLat: maximum latitude in decimal degrees (WGS 84) (Float)
minLon: minimum longitude in decimal degrees (WGS 84) (Float)
maxLon: maximum longitude in decimal degrees (WGS 84) (Float)

Example box-shaped region

{
    minLat: 40.51757813,
    maxLat: 40.86914063,
    minLon: -73.65234375,
    maxLon: -72.94921875,
}

circle

Define a circular region by specifying a record containing the following properties:

lat: latitude of the circle center in decimal degrees (WGS 84) (Float)
lon: longitude of the circle center in decimal degrees (WGS 84) (Float)
radius: radius of the circle in kilometers (km) (Float)

Example circular region

{
    lat: 40.69335938,
    lon: -73.30078125,
    radius: 20.0,
}

polygon

Define a polygonal region with a record containing the latitude and longitude for each point in the polygon:

points: points that define the custom polygon (Array of records)

Define each point with a record containing the following properties:

- **lat**: latitude in decimal degrees (WGS 84) _(Float)_
- **lon**: longitude in decimal degrees (WGS 84) _(Float)_

Example polygonal region

{
    points: [
        {lat: 40.671659, lon: -73.936631},
        {lat: 40.706543, lon: -73.749177},
        {lat: 40.791333, lon: -73.880327},
    ]
}

Strict and non-strict filtering

In most cases, the specified geographic region does not perfectly align with S2 grid cells.

Non-strict filtering returns points that may be outside of the specified region but inside S2 grid cells partially covered by the region.
Strict filtering returns only points inside the specified region.

Strict filtering is less performant, but more accurate than non-strict filtering.

S2 grid cell
Filter region
Returned point

Strict filtering