Projection tools

This section describes projection tools that are common to Rasters and Vectors, and facilitate geospatial analysis.

Get a metric coordinate system

A local metric coordinate system can be estimated for both Rasters and Vectors through the get_metric_crs() function.

The metric system returned can be either “universal” (zone of the Universal Transverse Mercator or Universal Polar Stereographic system), or “custom” (Mercator or Polar projection centered on the Raster or Vector).

import geoutils as gu

# Initiate a raster from disk
rast = gu.Raster(gu.examples.get_path("exploradores_aster_dem"))
rast.info()

# Estimate a universal metric CRS for the raster
rast.get_metric_crs()

Driver:               GTiff 
Opened from file:     /home/docs/checkouts/readthedocs.org/user_builds/geoutils/checkouts/latest/examples/data/Exploradores_ASTER/AST_L1A_00303182012144228_Z.tif 
Filename:             /home/docs/checkouts/readthedocs.org/user_builds/geoutils/checkouts/latest/examples/data/Exploradores_ASTER/AST_L1A_00303182012144228_Z.tif 
Loaded?               False 
Modified since load?  False 
Grid size:                 539, 618
Number of bands:      1
Data types:           float32
Coordinate system:    ['EPSG:32718']
Nodata value:         -9999.0
Pixel interpretation: Area
Pixel size:           30.0, 30.0
Upper left corner:    627175.0, 4833545.0
Lower right corner:   643345.0, 4852085.0

<Projected CRS: EPSG:32718>
Name: WGS 84 / UTM zone 18S
Axis Info [cartesian]:
- E[east]: Easting (metre)
- N[north]: Northing (metre)
Area of Use:
- name: Between 78°W and 72°W, southern hemisphere between 80°S and equator, onshore and offshore. Argentina. Brazil. Chile. Colombia. Ecuador. Peru.
- bounds: (-78.0, -80.0, -72.0, 0.0)
Coordinate Operation:
- name: UTM zone 18S
- method: Transverse Mercator
Datum: World Geodetic System 1984 ensemble
- Ellipsoid: WGS 84
- Prime Meridian: Greenwich

Get projected bounds

Projected bounds can be directly derived from both Rasters and Vectors through the get_bounds_projected() function.

# Get raster bounds in geographic CRS by passing its EPSG code
rast.get_bounds_projected(4326)

BoundingBox(left=-73.34341974540035, bottom=-46.639587475004994, right=-73.1271672077634, top=-46.469563567694934)

Important

When projecting to a new CRS, the footprint shape of the data is generally deformed. To account for this, use get_footprint_projected() described below.

Get projected footprint

A projected footprint can be derived from both Rasters and Vectors through the get_footprint_projected() function.

For this, the original rectangular footprint polygon lines are densified to respect the deformation during reprojection.

# Get raster footprint in geographic CRS
rast_footprint = rast.get_footprint_projected(4326)

rast_footprint.plot()

This is for instance useful to check for intersection with other data.