karta 0.7.1

Geospatial analysis in Python

Karta is a package for spatial analysis in Python. It streamlines data processing by providing efficient generic geographical types for vector and raster sources as well as a selection of analysis functions.

For example, read or create vector geometries:

point = Point((-130.0, 52.0), crs=LonLatWGS84)
line = read_geojson("linedata.json")
polygon = Polygon([(-515005.78, -1301130.53),
                   (-579174.89, -1282271.94),
                   (-542977.83, -1221147.82),
                   (-437864.05, -1251641.55),
                   (-438160.72, -1252421.48),
                   (-437961.28, -1285314.00)],
                   crs=NSIDCNorth)

Perform simple queries:

point2 = Point((-25.0, 48.0), crs=LonLatWGS84)
point.distance(point2)          # Distance in geographical units
line.intersects(polygon)        # True or False
ch = polygon.convex_hull()      # Returns a new polygon
ch.to_shapefile("poly.shp")

Load and manipulate raster data:

grid = read_gtiff("landsat_scene.tif")  # Leverages GDAL
grid.profile(line)              # Collect data along a line
grid.resample(500.0, 500.0)     # Return a grid resampled at a new resolution

Documentation

See the online manual, the tutorial, or read the API documentation.

The manual can be built offline using Sphinx. Building the documentation requires numpydoc.

Package Overview

• karta.crs: framework for coordinate reference systems and geodetic calculations

• karta.vector.geometry: geometry classes Point, Multipoint, Line, and Polygon with associated methods such as length, area, intersections, membership testing, convex hulls, and affine transformations

• karta.raster.grid: Grid classes including RegularGrid class (supporting CRS-aware clipping, sampling, profiling along vector tracks), and experimental WarpedGrid

• tests: unit tests, to be run with python tests/runtests.py

Formats

Karta provides a basic working interface to several of common file formats. Currently implemented are:

• vector

  • GeoJSON (r,w)

  • ESRI Shapefiles (via GDAL) (r,w)

  • GPS eXchange (GPX) (r,w)

• raster

  • GeoTiff (via GDAL) (r,w)

  • ESRI ASCII Grid (r,w)

Karta implements the Python `__geo_interface__ attribute <https://gist.github.com/sgillies/2217756>`__ for vector geometries. This permits data to be exchanged between Karta and external modules that also implement __geo_interface__ (e.g. shapely, fastkml).

Installation

The easiest way to install in production is via pip. Installation requires a recent version of setuptools:

pip install -U setuptools

Then, to install the latest release from PyPI:

pip install karta

Building from source

Building from source requires Cython:

pip install Cython

Then, clone the repository and install:

git clone https://github.com/fortyninemaps/karta.git karta
pip install -r karta/requirements.txt
pip install karta/

Dependencies

• numpy >= >1.7

• gdal >= 1.10

• pyproj >= 1.9

• blosc >= 1.2

• C99-compliant compiler

Karta supports Python 2.7 and Python 3.4+.