Transcript
Python GeoSpatial Analysis
https://www.jasondavies.com/maps/transition/
GeoSpatial Python• GeoSpatial analysis• Key concepts
• Representations of the earth• Projections• Coordinate Systems• Geometry• Remote Sensing • GeoFunctions
• Software • Geo Foundations• Python
About me• by day
• Traveling salesman in wireless communications • Network neurologist• Mobile networking
• by night• Pythonista (middling)• Music • Photography
• Education• West Windsor Plainsboro High School• Thomas Edison State College, BSBA• Lehigh University, MBA
DonHolloway
DonHolloway
DonHolloway
Geospatial Fundamentals• Statistical analysis + place• Spatial
• Points of Interest• Geolocation• Geometry
• Analysis• Big Data• Familiar tools
• Numpy• Pandas• Pillow
• Visualization
Terrestrial scale - shape and sizeNaming of placesNeed for rigour – coordinate systems and datums2D vs 3D perspectives on geospatial issues
Representations of the Earth Map Globe Oblate Spheroid
datum• a set of reference points on the Earth's surface against which position
measurements are made• North American Datum of 1927 (NAD27)• NAD83 (adopted internationally as GRS80)• World Geodetic System 1984 (WGS84)
ProjectionsProjections convert spherical coordinates (lat-long) to planar coordinates.
Three primary types:• Azimuthal: projection onto a planar surface• Cylindrical: projection onto a cylinder, which is then ‘unrolled’ to a plane.• Conic: projection onto a cone, which can be unrolled to a plane.
All projections create distortions of shape, area, or distanceWeb Mercator (EPSG:3857) – Used by Google maps, OpenStreet Maps• Cylindrical – Uses ellipsoidal coordinate data, spherical calculations
Coordinate Systems• Geographic (Lat-Long)
• UTM (Universal Transverse Mercator) • Worldwide system with units in meters• In Northern hemisphere, Y coordinate (northing) is distance in meters from equator• X-coordinate (easting) is distance in meters east from a central meridian for a zone• Consists of 60 zones each 6 degrees wide
• State Plane Coordinate System (SPCS) • Different for each state• Some states divided into multiple zones with different grid systems for each zone• Either Transverse Mercator (NJ) or conical (PA * 2) projections
Geometry (vectors)• Vector Data
• Points, Lines, Polygons• Spatial representation
• WKT, WKB• Simple features spec
• Points of Interest• Shapefiles
• Semi Proprietary• Loosely structured• Decades of data
• GeoJSON• Emerging open standard
• Tools• GEOS / Shapely• OGR / Fiona• Geojson• PyShp• dbfpy
https://njgin.state.nj.us/NJ_NJGINExplorer/index.jsp
NJ MunicipalitiesEarthquake epicenters
Remote Sensing Imagery(Raster)• “Image-like”• Typical formats
• TIFF (tags inherent)• JPEG (exif), GIF, BMP and PNG(world files)
• Alternates• BLOB, NetCDF
• Resolution is specified in ground distance thateach cell represents• GDAL / Pillow / OpenCV
Landsat 8 – acquired 2/2/2016
Geospatial functions• Bounding Box• Convex Hull• Buffer / erode• Dissolve• Generalize• Intersection• Merge• Point in Polygon• Union
Environment:WindowsPython 3.4Anaconda package
Software• Geo Foundations• GDAL,OGR, Geos, PROJ4
• Geo General Purpose• QGIS, PostGIS, MapServer
• Analysis• Pandas, Numpy, Pillow, PostGIS, Matplotlib
• Python • geoPandas*(pandas), shapely (geos), pyproj(proj4), Fiona(OGR), geopy
(geolocation), Descartes(matplotlib),
References• Resources• Wikipedia list of GIS software - et.gy/1Q327gk• OSGeo project list – www.osgeo.org/
• Data• NJ Shape files - https://njgin.state.nj.us/NJ_NJGINExplorer/index.jsp• Raster images - http://earthexplorer.usgs.govPython libraries/
• Shapely http://toblerity.org/shapely
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