1. Get the region (bounding box) of a set of points

Let’s say we have a dataset that has longitude and latitude coordinates (but it could also be whatever other type of coordinate). And we need to know the bounding box of this dataset, which we call a region, comprised of West, East, South, and North values. Bordado offers bordado.get_region to do this.

import ensaio
import pandas as pd
import bordado as bd

To demonstrate, we’ll use ensaio.fetch_southern_africa_gravity to get a sample dataset of ground-based gravity observation across Southern Africa. The dataset is a CSV file, which we’ll load using pandas.read_csv:

fname = ensaio.fetch_southern_africa_gravity(version=1)
data = pd.read_csv(fname)
data

	longitude	latitude	height_sea_level_m	gravity_mgal
0	18.34444	-34.12971	32.2	979656.12
1	18.36028	-34.08833	592.5	979508.21
2	18.37418	-34.19583	18.4	979666.46
3	18.40388	-34.23972	25.0	979671.03
4	18.41112	-34.16444	228.7	979616.11
...	...	...	...	...
14354	21.22500	-17.95833	1053.1	978182.09
14355	21.27500	-17.98333	1033.3	978183.09
14356	21.70833	-17.99166	1041.8	978182.69
14357	21.85000	-17.95833	1033.3	978193.18
14358	21.98333	-17.94166	1022.6	978211.38

14359 rows × 4 columns

We can then use get_region to extract the bounding box information:

coordinates = (data.longitude, data.latitude)
region = bd.get_region(coordinates)
print(region)

(11.90833, 32.74667, -34.996, -17.33333)

The region above will have the minimum and maximum values of each coordinate in order. The order of the coordinates will be the order of the output region. In this case, the numbers correspond to the West and East longitude, followed by the South and North latitude.

Note

We tend to always use “longitude” or “easting” and then “latitude” or “northing” as the order of coordinates. But Bordado can work with whatever order you choose:

coordinates = (data.latitude, data.longitude)
region = bd.get_region(coordinates)
print(region)

(-34.996, -17.33333, 11.90833, 32.74667)

Just be aware of your own conventions.

If the height_sea_level_m column is considered another coordinate and we want the 3D bounding box, we can pass more than 2 values to get_region:

coordinates_3d = (data.longitude, data.latitude, data.height_sea_level_m)
region_3d = bd.get_region(coordinates_3d)
print(region_3d)

(11.90833, 32.74667, -34.996, -17.33333, 0.0, 2622.2)

In this case, the minimum and maximum height are the two last values of the region_3d tuple.