perrygeo

Avoiding padding errors with Python's base64 encoding

>>> import base64
>>> data = '{"u": "test"}'
>>> code = base64.b64encode(data)
>>> code
'eyJ1IjogInRlc3QifQ=='

perrygeo

This is a proof-of-concept for a numpy/rasterio/shapely based implementation of partial coverage rasterization. It works, barely.

The current GDAL algorithms allow for two methods, both binary: the default centroid method and the all-touched method.

This is a third alternative which provides the percentage of coverage of each cell from 0 to 100 which can be thought of as pixel weights for many spatial analyses.

See discussion at rasterio/rasterio#232

perrygeo

Loading spatialite tables into GeoPandas GeoDataFrames

This little trick derives from the fact that the from_postgis class method is not really specific to postgis at all; it will work with sqlalchmey or dbapi2 connections. However, there are some peculiarities with spatialite that prevent this from being as simple as one might hope. There are two options:

• The pysqlite2 driver works great for vanilla sqlite3 databases but spatialite requires loading an extension. In order to load extensions, you need to install a patched version and do some manual loading of the shared library. (see the_pysqlite2_way.py)

• A better alternative is to use pyspatialite but installation is also a bit funky. I had to install from the current git master instead of the pypi version. The extension is loaded automatically. (see the_pyspatialite_way.py)

perrygeo

apt-get install python-pygraphviz
pip install django-extensions
# add 'django_extensions' to INSTALLED_APPS in settings.py
python manage.py graph_models trees -o test.png

perrygeo

# Using osm.pbf extracts from https://download.geofabrik.de/index.html
# Requires GDAL 3.7+ with the TileDB driver

ogr2ogr -f TileDB ./dc-lines district-of-columbia-latest.osm.pbf lines
ogr2ogr -f TileDB ./dc-points district-of-columbia-latest.osm.pbf points
ogr2ogr -f TileDB ./dc-polygons district-of-columbia-latest.osm.pbf multipolygons

perrygeo

perrygeo

"""
Zonal Statistics
Vector-Raster Analysis

Copyright 2013 Matthew Perry

Usage:
  zonal_stats.py VECTOR RASTER
  zonal_stats.py -h | --help
  zonal_stats.py --version

perrygeo

FROM python:3.6-slim-stretch

ADD requirements.txt /tmp/requirements.txt

RUN apt-get update && \
    apt-get install -y \
        build-essential \
        make \
        gcc \
        locales \

perrygeo

"""
Web Mercator Scale and Resolution Calculations
Python implementation of the formulas at http://msdn.microsoft.com/en-us/library/bb259689.aspx
"""
import math

def meters_per_pixel(zoom, lat):
    """
    ground resolution = cos(latitude * pi/180) * earth circumference / map width
    """

perrygeo

DROP TABLE if EXISTS boundaries;

CREATE TABLE boundaries (
    id BIGSERIAL primary key,
	geometry geometry(multipolygon, 4326) NOT null
);

CREATE INDEX idx_boundaries_geometry
ON boundaries
USING gist (geometry);