telluric¶
Interactive vector and raster geospatial data manipulation in Python¶
Guy Doulberg - 2018-06-04 @ PyCon-IL¶
https://github.com/satellogic/telluric-talks
Satellogic¶
- We are building a constellation of satellites that orbits earth.
- We are building an infrastructure to collect and store data (mostly images) from this constellation.
- We are producing insights out of this data and other sources of data.
- We are hiring
Guy¶
- I am part of the team which is responsilbe for collecting storing and accesing the Raster and Vector Data in Satellogic.
- Software engineer with experience in big data projects.
1. Quick intro to geospatial data¶
Geospatial data, geographic data, georeferenced data, or just geodata "are defined in the ISO/TC 211 series of standards as data and information having an implicit or explicit association with a location relative to the Earth"
-- https://en.wikipedia.org/wiki/Geographic_data_and_information
A geographic information system (GIS) is a system designed to capture, store, manipulate, analyze, manage, and present spatial or geographic data.
-- https://en.wikipedia.org/wiki/Geographic_information_system
Two forms: vector and raster¶
- Vector data:
- Defining shapes
- Raster data:
- Assigning pixels values
Image by Víctor Olaya "Sistemas de Información Geográfica", CC-BY
Vector data¶
- Entities: Points, Lines and Polygons
- Common formats: ESRI Shapefiles, GeoJSON, TopoJSON, ...
Image by M. W. Toews https://en.wikipedia.org/wiki/File:Simple_vector_map.svg, CC-BY
GEO referenced¶
- Vectors and Rasters can exist in fields other than GIS.
- The are part of a GIS when they are Geo-Referenced.
- For example:
- A Polygon is Geo-Referenced when you know how to draw it on earth
- A Raster is Geo-Referenced when you know where is the raster located
Projections¶
A method to locate points on earth
TL;DR: A mess.
- The Earth is approximately a sphere, which is not a developable surface (i.e. it cannot be flattened onto a plane without distortion)
- Therefore, we need projections that attempt to represent the Earth on a plane, with various tradeoffs and limitations
2. Why yet another Existing software¶
The landscape is complicated and somewhat difficult to navigate at times:
Summary of key libraries:
| Python | C/C++ | |
|---|---|---|
| pyproj | ⇒ | PROJ.4 |
| Fiona | ⇒ | OGR |
| Shapely | ⇒ | GEOS |
| rasterio | ⇒ | GDAL |
3. telluric library¶
telluric is an open source (MIT) Python library to manage vector and raster geospatial data in an interactive and easy way.
- Projection-aware geometric operations
- Simple I/O for raster and vector data
- Interactive visualization
- 🕮 Documentation http://telluric.readthedocs.io/
- 🔧 Source https://github.com/satellogic/telluric
Importing for interactive use is short:
In [1]:
import telluric as tl
from telluric.constants import WGS84_CRS, WEB_MERCATOR_CRS
Basic geometry definition using GeoVector: in the simplest case, the bounds and the projection (CRS)
In [2]:
gush_dan = tl.GeoVector.from_bounds(
xmin=34.6, ymin=32, xmax=35.0, ymax=32.3, crs=WGS84_CRS
)
print(gush_dan)
GeoVector(shape=POLYGON ((34.6 32, 34.6 32.3, 35 32.3, 35 32, 34.6 32)), crs=CRS({'init': 'epsg:4326'}))
We added extra attention to Jupyter noteobook visualization, checkout this plot¶
In [3]:
gush_dan
/home/guyd/pEnvs/telluric-dev/local/lib/python3.5/site-packages/telluric/plotting.py:141: UserWarning: Plotting a limited representation of the data, use the .plot() method for further customization "Plotting a limited representation of the data, use the .plot() method for further customization")
Out[3]:
Using Shapely geometries is also allowed:
In [4]:
from shapely.geometry import Polygon
south_tlv = tl.GeoVector(
Polygon([(34.75, 32.04), (34.75, 32.06), (34.77,32.06), (34.77, 32.04), ( 34.75, 32.04)]),
WGS84_CRS
)
south_tlv
/home/guyd/pEnvs/telluric-dev/local/lib/python3.5/site-packages/telluric/plotting.py:141: UserWarning: Plotting a limited representation of the data, use the .plot() method for further customization "Plotting a limited representation of the data, use the .plot() method for further customization")
Out[4]:
Access several properties:¶
In [5]:
gush_dan.centroid
/home/guyd/pEnvs/telluric-dev/local/lib/python3.5/site-packages/telluric/plotting.py:141: UserWarning: Plotting a limited representation of the data, use the .plot() method for further customization "Plotting a limited representation of the data, use the .plot() method for further customization")
Out[5]:
In [6]:
gush_dan.area # Real area in square meters
Out[6]:
1259014132.9260154
Geomteric Relations¶
In [7]:
gush_dan.within(south_tlv)
Out[7]:
False
In [8]:
south_tlv.within(gush_dan)
Out[8]:
True
In [9]:
print(south_tlv.difference(gush_dan))
GeoVector(shape=GEOMETRYCOLLECTION EMPTY, crs=CRS({'init': 'epsg:4326'}))
In [10]:
gush_dan.difference(south_tlv)
/home/guyd/pEnvs/telluric-dev/local/lib/python3.5/site-packages/telluric/plotting.py:141: UserWarning: Plotting a limited representation of the data, use the .plot() method for further customization "Plotting a limited representation of the data, use the .plot() method for further customization")
Out[10]:
- Features:
GeoVector+ attributes FeatureCollections: a sequence of features
In [11]:
gf1 = tl.GeoFeature(
gush_dan,
{'district': 'גוש דן'}
)
gf2 = tl.GeoFeature(
south_tlv,
{'city': 'תל אביב'}
)
print(gf1)
print(gf2)
GeoFeature(Polygon, {'district': 'גוש דן'})
GeoFeature(Polygon, {'city': 'תל אביב'})
In [12]:
fc = tl.FeatureCollection([gf1, gf2])
fc
/home/guyd/pEnvs/telluric-dev/local/lib/python3.5/site-packages/telluric/plotting.py:141: UserWarning: Plotting a limited representation of the data, use the .plot() method for further customization "Plotting a limited representation of the data, use the .plot() method for further customization")
Out[12]:
Raster data:¶
In [13]:
# This will only save the URL in memory
rs = tl.GeoRaster2.open(
"https://github.com/mapbox/rasterio/raw/master/tests/data/rgb_deflate.tif"
)
# These calls will fecth some GeoTIFF metadata
# without reading the whole image
print(rs.crs)
print(rs.band_names)
CRS({'init': 'epsg:32618'})
[0, 1, 2]
In [14]:
rs.footprint() # is the bouding box
/home/guyd/pEnvs/telluric-dev/local/lib/python3.5/site-packages/telluric/plotting.py:141: UserWarning: Plotting a limited representation of the data, use the .plot() method for further customization "Plotting a limited representation of the data, use the .plot() method for further customization")
Out[14]:
In [15]:
rs
Out[15]: