wcs 0.2.0

Python client library for WCS (OGC Web Coverage Service) backends.

from docutils.nodes import description

Overview

The OGC Web Coverage Service (WCS) standard defines support for modeling and retrieval of geospatial data as coverages (e.g. sensor, image, or statistics data).

This Python library allows to extract information about WCS coverages from a given WCS endpoint.

Installation

pip install wcs

Examples

The example below illustrates how to get a list of BasicCoverage objects for all coverages on the server, and extract various details for a particular coverage.

from wcs.service import WebCoverageService
from wcs.model import Crs

wcs_endpoint = "https://ows.rasdaman.org/rasdaman/ows"
service = WebCoverageService(wcs_endpoint)

# get a list of all coverages, with basic information such
# as a WGS 84 bounding box and a native bounding box
coverages = service.list_coverages()

# get the AvgLandTemp coverage object, see BasicCoverage
# in the API reference
avg_land_temp = coverages['AvgLandTemp']

# print all information
print(avg_land_temp)

# AvgLandTemp:
#   subtype: ReferenceableGridCoverage
#   native CRS: OGC:AnsiDate+EPSG:4326
#   geo bbox:
#     ansi:
#       min: "2000-02-01"
#       max: "2015-06-01"
#       crs: OGC:AnsiDate
#     Lat:
#       min: -90
#       max: 90
#       crs: EPSG:4326
#     Lon:
#       min: -180
#       max: 180
#       crs: EPSG:4326
#   lon/lat bbox:
#     Lon:
#       min: -180
#       max: 180
#       crs: EPSG:4326
#     Lat:
#       min: -90
#       max: 90
#       crs: EPSG:4326
#   size in bytes: 4809618404

# coverage subtype
print(avg_land_temp.subtype)
# ReferenceableGridCoverage

# coverage bounding box, containing the CRS and axes
bbox = avg_land_temp.bbox

# full coverage crs identifier
print(bbox.crs)
# https://www.opengis.net/def/crs-compound?
# 1=https://www.opengis.net/def/crs/OGC/0/AnsiDate&
# 2=https://www.opengis.net/def/crs/EPSG/0/4326

# coverage crs identifier in shorthand notation
print(Crs.to_short_notation(bbox.crs))
# OGC:AnsiDate+EPSG:4326

# get information for the first axis; as it is a temporal axis,
# the lower_bound and upper_bound are datetime.datetime objects.
axis = bbox[0]
name = axis.name
lower_bound = axis.low
upper_bound = axis.high
print(f'{name}({lower_bound} - {upper_bound})')
# ansi(2000-02-01 00:00:00+00:00 - 2015-06-01 00:00:00+00:00)

# get information for the Lat axis
axis = bbox['Lat']
print(axis.name)
# Lat

# get size in bytes if available
if avg_land_temp.size_bytes is not None:
    print(avg_land_temp.size_bytes)
    # 4809618404

The above example gets basic information about the coverage through what is published in the WCS GetCapabilities response. More detailed information can be retrieved with the list_full_info method, which returns a FullCoverage object.

from wcs.service import WebCoverageService

wcs_endpoint = "https://ows.rasdaman.org/rasdaman/ows"
service = WebCoverageService(wcs_endpoint)

# get full information for a particular coverage by
# parsing its DescribeCoverage document from the WCS server
full_avg_land_temp = service.list_full_info('AvgLandTemp')

# print all information
print(full_avg_land_temp)

# AvgLandTemp:
#   native CRS: OGC:AnsiDate+EPSG:4326
#   geo bbox:
#     ansi:
#       min: "2000-02-01"
#       max: "2015-06-01"
#       crs: OGC:AnsiDate
#       uom: d
#       type: irregular
#       coefficients: ["2000-02-01", "2000-03-01", ...
#                      "2015-05-01", "2015-06-01"]
#     Lat:
#       min: -90
#       max: 90
#       crs: EPSG:4326
#       uom: degree
#       resolution: -0.1
#       type: regular
#     Lon:
#       min: -180
#       max: 180
#       crs: EPSG:4326
#       uom: degree
#       resolution: 0.1
#       type: regular
#   grid bbox:
#     i:
#       min: 0
#       max: 184
#       resolution: 1
#       type: regular
#     j:
#       min: 0
#       max: 1799
#       resolution: 1
#       type: regular
#     k:
#       min: 0
#       max: 3599
#       resolution: 1
#       type: regular
#   range type fields:
#     Gray:
#       type: Quantity
#       label: Gray
#       definition: http://www.opengis.net/def/dataType/OGC/0/float32
#       nil values: 99999
#       uom: 10^0
#   metadata:
#     {
#       "covMetadata": null
#     }


# In addition to the geo bounding box in native CRS, the 
# `FullCoverage` object also has a `grid_bbox`, which contains 
# the integer grid axis bounds of the coverage. This is the same 
# type of `BoundingBox` object, except the `crs` is None.
print(full_avg_land_temp.grid_bbox)

# The range_type indicates the structure of the cell values
# of the coverage. It contains a `fields` attribute, which is
# a list of `Field` object corresponding to the bands of the 
# coverage. Check the documentation of RangeType for full details.
range_type = full_avg_land_temp.range_type
all_fields = range_type.fields
field = range_type['Gray']  # or range_type[0]

# get all properties of the field
label = field.label
description = field.description
definition = field.definition
nil_values = field.nil_values
if field.is_quantity:
  uom = field.uom
else:
  codespace = field.codespace

Contributing

The directory structure is as follows:

• wcs - the main library code
• tests - testing code
• docs - documentation in reStructuredText format

Tests

To run the tests:

# install dependencies
pip install wcs[tests]

pytest

Documentation

To build the documentation:

# install dependencies
pip install wcs[docs]

cd docs
make html

The built documentation can be found in the docs/_build/html/ subdir.