The Geospatial Landscape
OverviewTeaching: 10 min
Exercises: 0 minQuestions
What programs and applications are available for working with geospatial data?Objectives
Describe the difference between various approaches to geospatial computing, and their relative strengths and weaknesses.
Name some commonly used GIS applications.
Name some commonly used Python packages that can access and process spatial data.
Describe pros and cons for working with geospatial data using a command-line versus a graphical user interface.
Standalone Software Packages
Most traditional GIS work is carried out in standalone applications that aim to provide end-to-end geospatial solutions. These applications are available under a wide range of licenses and price points. Some of the most common are listed below.
The Open Source Geospatial Foundation (OSGEO) supports several actively managed GIS platforms:
- QGIS is a professional GIS application that is built on top of and proud to be itself Free and Open Source Software (FOSS). QGIS is written in Python, has a python console interface, and has several interfaces written in R including RQGIS.
- GRASS GIS, commonly referred to as GRASS (Geographic Resources Analysis Support System), is a FOSS-GIS software suite used for geospatial data management and analysis, image processing, graphics and maps production, spatial modeling, and visualization. GRASS GIS is currently used in academic and commercial settings around the world, as well as by many governmental agencies and environmental consulting companies. It is a founding member of the Open Source Geospatial Foundation (OSGeo). GRASS GIS can be installed along with and made accessible within QGIS 3.
- GDAL is a multiplatform set of tools for translating between geospatial data formats. It can also handle reprojection and a variety of geoprocessing tasks. GDAL is built in to many applications both FOSS and commercial, including GRASS and QGIS.
- SAGA-GIS, or System for Automated Geoscientific Analyses, is a FOSS-GIS application developed by a small team of researchers from the Dept. of Physical Geography, Göttingen, and the Dept. of Physical Geography, Hamburg. SAGA has been designed for an easy and effective implementation of spatial algorithms, offers a comprehensive, growing set of geoscientific methods, provides an easily approachable user interface with many visualisation options, and runs under Windows and Linux operating systems. Like GRASS GIS, it can also be installed and made accessible in QGIS3.
- PostGIS is a geospatial extension to the PostGreSQL relational database.
- ESRI (Environmental Systems Research Institute) is an international supplier of geographic information system (GIS) software, web GIS and geodatabase management applications. ESRI provides several licenced platforms for performing GIS, including ArcGIS, ArcGIS Online, and Portal for ArcGIS a standalone version of ArGIS Online which you host locally. ESRI welcomes development on their platforms through their DevLabs. ArcGIS software can be installed using Chef Cookbooks from Github.
- Pitney Bowes produce MapInfo Professional, which was one of the earliest desktop GIS programs on the market.
- Hexagon Geospatial Power Portfolio includes many geospatial tools including ERDAS Imagine, powerful software for remote sensing.
- Manifold is a desktop GIS that emphasizes speed through the use of parallel and GPU processing.
Online + Cloud computing
- PANGEO is a community organization dedicated to open and reproducible data science with python. They focus on the Pangeo software ecosystem for working with big data in the geosciences.
- ArcGIS Online provides access to thousands of maps and base layers.
Private companies have released SDK platforms for large scale GIS analysis:
- Kepler.gl is Uber’s toolkit for handling large datasets (i.e. Uber’s data archive).
- Boundless Geospatial is built upon OSGEO software for enterprise solutions.
Publicly funded open-source platforms for large scale GIS analysis:
- PANGEO for the Earth Sciences. This community organization also supports python libraries like xarray, iris, dask, jupyter, and many other packages.
- Sepal.io by FAO Open Foris utilizing EOS satellite imagery and cloud resources for global forest monitoring.
GUI vs CLI
The earliest computer systems operated without a graphical user interface (GUI), relying only on the command-line interface (CLI). Since mapping and spatial analysis are strongly visual tasks, GIS applications benefited greatly from the emergence of GUIs and quickly came to rely heavily on them. Most modern GIS applications have very complex GUIs, with all common tools and procedures accessed via buttons and menus.
Benefits of using a GUI include:
- Tools are all laid out in front of you
- Complex commands are easy to build
- Don’t need to learn a coding language
- Cartography and visualisation is more intuitive and flexible
Downsides of using a GUI include:
- Low reproducibility - you can’t record your actions and replay
- Most are not designed for batch-processing files
- Limited ability to customise functions or write your own
- Intimidating interface for new users - so many buttons!
In scientific computing, the lack of reproducibility in point-and-click software has come to be viewed as a critical weakness. As such, scripted CLI-style workflows are again becoming popular, which leads us to another approach to doing GIS — via a programming language. This is the approach we will be using throughout this workshop.
GIS in programming languages
A number of powerful geospatial processing libraries exist for general-purpose programming languages like Java and C++. However, the learning curve for these languages is steep and the effort required is excessive for users who only need a subset of their functionality.
Higher-level scripting languages like Python and R are easier to learn and use. Both
now have their own packages that wrap up those geospatial processing libraries and make
them easy to access and use safely. A key example is the Java Topology Suite (JTS),
which is implemented in C++ as GEOS. GEOS is accessible in Python via the
geopandas, which makes use of
shapely) and in R via
sf. R and Python
also have interface packages for GDAL, and for specific GIS apps.
This last point is a huge advantage for GIS-by-programming; these interface packages give you the ability to access functions unique to particular programs, but have your entire workflow recorded in a central document - a document that can be re-run at will. Below are lists of some of the key spatial packages for Python, which we will be using in the remainder of this workshop.
geocubefor working with vector data
rioxarrayfor working with raster data
These packages along with the
matplotlib package are all we need for spatial data visualisation. Python also has many fundamental scientific packages that are relevant in the geospatial domain. Below is a list of particularly fundamental packages.
scikit-image are all excellent options for working with rasters, as arrays.
An overview of these and other Python spatial packages can be accessed here.
As a programming language, Python can be a CLI tool. However, using Python together with an Integrated Development Environment (IDE) application allows some GUI features to become part of your workflow. IDEs allow the best of both worlds. They provide a place to visually examine data and other software objects, interact with your file system, and draw plots and maps, but your activities are still command-driven: recordable and reproducible. There are several IDEs available for Python. JupyterLab is well-developed and the most widely used option for data science in Python. VSCode and Spyder are other popular options for data science.
Traditional GIS apps are also moving back towards providing a scripting environment for users, further blurring the CLI/GUI divide. ESRI have adopted Python into their software, and QGIS is both Python and R-friendly.
GIS File Types
There are a variety of file types that are used in GIS analysis. Depending on the program you choose to use some file types can be used while others are not readable. Below is a brief table describing some of the most common vector and raster file types.
|Esri ShapeFile||.SHP .DBF .SHX||The most common geospatial file type. This has become the industry standard. The three required files are: SHP is the feature geometry. SHX is the shape index position. DBF is the attribute data.|
|Google Keyhole Markup Language||.KML .KMZ||KML stands for Keyhole Markup Language. This GIS format is XML-based and is primarily used for Google Earth.|
|OpenStreetMap||.OSM||OSM files are the native file for OpenStreetMap which had become the largest crowdsourcing GIS data project in the world. These files are a collection of vector features from crowd-sourced contributions from the open community.|
|ERDAS Imagine||.IMG||ERDAS Imagine IMG files is a proprietary file format developed by Hexagon Geospatial. IMG files are commonly used for raster data to store single and multiple bands of satellite data.Each raster layer as part of an IMG file contains information about its data values. For example, this includes projection, statistics, attributes, pyramids and whether or not it’s a continuous or discrete type of raster.|
|GeoTIFF||.TIF .TIFF .OVR||The GeoTIFF has become an industry image standard file for GIS and satellite remote sensing applications. GeoTIFFs may be accompanied by other files:TFW is the world file that is required to give your raster geolocation.XML optionally accompany GeoTIFFs and are your metadata.AUX auxiliary files store projections and other information.OVR pyramid files improves performance for raster display.|
Many software packages exist for working with geospatial data.
Command-line programs allow you to automate and reproduce your work.
JupyterLab provides a user-friendly interface for working with Python.