This course provides an in depth overview of the application of Geographic Information Systems (GIS) to the marine environment using QGIS.
Aims and Objectives:
Provide an introduction to GIS for marine applications
Focus on some publicly available marine datasets
Show the potential applications of GIS for the marine environment
Knowledge and understanding of GIS, spatial data, raster and vector models
Core tasks involved in the GIS analysis process including data acquisition, management, manipulation and analysis, and presentation and output
Core functionality of QGIS Desktop and QGIS Browser
Creating and editing spatial data
Appreciation of coastal and marine GIS data applications
Introduction to Marine GIS
A Geographic Information System (GIS) is a technology for managing geographic, or spatial, data. It is an integrated set of hardware and software tools used for the capture, storage, analysis and display of geographic data. GIS technology integrates common database operations such as query and statistical analysis with the visualisation and geographic analysis benefits offered by maps and charts.
GIS Data Models. A data model in geographic information systems is a mathematical construct for representing geographic objects or surfaces as data. In this course you will use both vector and raster data.
Marine GIS Applications. Marine GIS plays an important role in our understanding of the environment, and in particular, the marine environment. Marine GIS can be adapted and utilized to assist researchers and organizations in managing spatial applications related to oceanographic and coastal problems by facilitating the process of creating and producing geospatial data including coastal shorelines and bottom sea bathymetric (Oceanteacher Digital Library). An excellent publication that focuses on the potential and progress of GIS research in the marine and coastal realm is Marine and Coastal Geographical Information Systemsedited by Dawn Wright and Darius Bartlett. Marine GIS can cover a wide range of of applications and can be categorized, for example, as coastal, oceanographic or fisheries (OceanTeacher Digital LIbrary). See also Geospatial Technology for Coastal Environments from ESRI.
As information becomes increasingly spatially aware, there is no shortage of tools able to fulfill some or all commonly used GIS functions. Why should anyone be using QGIS over some other GIS software package?
Here are only some of the reasons:
It’s free, as in lunch. Installing and using the QGIS program costs you a grand total of zero money. No initial fee, no recurring fee, nothing.
It’s free, as in liberty. If you need extra functionality in QGIS, you can do more than just hope it will be included in the next release. You can sponsor the development of a feature, or add it yourself if you are familiar with programming.
It’s constantly developing. Because anyone can add new features and improve on existing ones, QGIS never stagnates. The development of a new tool can happen as quickly as you need it to.
Extensive help and documentation is available. If you’re stuck with anything, you can turn to the extensive documentation, your fellow QGIS users, or even the developers.
Cross-platform. QGIS can be installed on MacOS, Windows and Linux.
Now that you know why you want to use QGIS.
View data in QGIS Desktop
Main windows: QGIS provides several windows, convenient for the user. Main windows of QGIS include:
Data displaying and managing Windows; in these windows there are subwindows as follows:
üWindow for managing data layers (layers)
üWindow for data browser (Browser)
üWindow for displaying attribute (Attribute Table)
Map Projections and Coordinate Systems
A geographic coordinate system defines locations on the earth using a three-dimensional spherical surface. A coordinate system includes an angular unit of measure, a prime meridian, and a datum (based on a spheroid). A feature is referenced by its longitude and latitude values. Longitude and latitude are angles measured from the earth’s centre to a point on the earth’s surface measured in degrees. See Geolocation by Latitiude and Longitude (OceanTeacher Digital Library).
In a GIS every dataset has a coordinate system which is used to integrate it with other geographic data layers within a common coordinate framework. Coordinate systems enable you to perform various analytical operations such as overlaying data layers from disparate sources and coordinate systems. There are two common types of coordinate systems used in GIS:
A global or spherical coordinate system such as latitude-longitude, often referred to as a geographic coordinate system.
A projected coordinate system which project a map of the earth's spherical surface onto a two-dimensional Cartesian coordinate plane. Projected coordinate systems are referred to as map projections.
Geographic Coordinate Systems. A geographic coordinate system is a coordinate system that enables every location on the Earth to be specified by a set of numbers (Wikipedia). The exercises in this course will be using geographic (or unprojected) coordinate system using a rectangular latitude and longitude grid.
As a first step to developing a national marine data collection it is necessary to define the Area of Interest (AOI). There are a number of resources where you can download base map data. Some examples are high resolution country data (including administrative boundaries, roads, railways, land cover and population density), global bathymetry contours and coastline, and global EEZ boundaries. These data layers are available as shapefiles and can be used directly in ArcMap.
All exercises in this course will be based around the West African country of Liberia. The methods used here, however, can be used for your own area of interest.
Creating Data Collection from the World Ocean Database
The World Ocean Database Project, or WOD, is a project established by the Intergovernmental Oceanographic Commission (IOC). WOD represents the world’s largest collection of ocean profile-plankton data available internationally without restriction with data coming from the National Oceanographic Data Centres (NODCs) of IODE as well as other international programmes such as World Ocean Circulation Experiment (WOCE) and Joint Global Ocean Flux Study (JGOFS), CLIVAR , Argo, Global Temperature-Salinity Profile Project (GTSPP). See World Ocean Database and World Ocean Atlas (OceanTeacher Digital Library).
The data in the World Ocean Database are made available through the online search and retrieval system known as WODselect. The WODselect retrieval system allows a user to search World Ocean Database 2009 and new data added since its release using a user-specified search criteria. A distribution map and cast count of these search criteria will give the user the option to have the data extracted and placed on the NODC FTP site in the WOD09 native and ".csv" data format.
Introduction to Ocean Data View
Ocean Data View (ODV) is a software package for the interactive exploration, analysis and visualization of oceanographic and other geo-referenced profile or sequence data. ODV can display original data points or gridded fields based on the original data. ODV can be downloaded here. You will need to register as a member of the ODV users group first.
This exercise will briefly introduce ODV to create an ODV collection from the World Ocean Database and then export the data from ODV so it can be used in ArcGIS.
You can learn more about ODV watching this .
Correction for Exercise: Exporting Marine Data from ODV : Data Subsets
Step no 9. Select EXPORT>STATION DATA>ODV SPREADSHEET FILE.
Note: Liberia has two distinct seasons: a wet season (referred to as the West African Monsoon) between May and November where the dominant wind direction is south‐westerly, blowing moist air from the Atlantic onto the continent. In the winter, the dominant wind direction is reversed, when the winds blow from the Sahara desert. For these exercises you will select data for the wet season (June, July, August) and the dry season (January, February, March).
In step 6 select Season:
i) from Jan/01 to Mar/31 ii) from Jun/01 to Aug/30
Create separate files for surface (0m) and 400m for temperature and salinity:
NOTE: When exporting data from ODV make sure the box "Use compact output format" is NOT checked.
Working with Spreadsheet Data
Tables containing X and Y coordinates (Longitude and Latitude) and ocean parameters can be imported into QGIS and converted to a shapefile. The ocean parameters that have been extracted from World Ocean Database and processed in Ocean Data View will be used in this exercise.
Edit Data in QGIS
QGIS includes some basic editing functions that allows you to create and edit several kinds of feature geometry data including points, lines, polygons, text , and tables. When you edit in QGIS, the entire workspace, that is, all the layers in the workspace are available for editing.
This tutorial introduces some basic skills needed to proceed with editing in QGIS.
Edit Data: Area of Interest and Analysis Mask
ArcMap editing functions allows you to create new shape files. This exercise will use the ArcMap edit tools to create a polygon to define the area of interest and a landmask polygon to represent the land area that will be used to hide land-based features.
Interpolation is process by which a surface is created, usually as a raster dataset, through the input of data collected at a number of sample points in addition to computed points. There are different ways to derive prediction by interpolation function, for example, linear, IDW, spline, kriging. Read the article on Map Interpolation in OceanTeacher and Understanding Raster Interpolation (ESRI).
When a raster dataset layer is added toQGIS, it is displayed using the default renderer most appropriate for the raster layer. QGIS allows you to choose from different drawing methods based on your display and analysis needs. You can change display colours, group data values into classes, or stretch values to increase the visual contrast. This exercise will use the Stretched renderer to display continuous raster cell values across a gradual ramp of colours.
The Raster Calculator, which is part of the Spatial Analyst extension, provides a powerful tool for performing mathematical calculations using operators and functions, set up selection queries, or type in Map Algebra syntax. Inputs can be raster datasets or raster layers, coverages, shapefiles, tables, constants, and numbers.
Map algebra provides tools to perform spatial analysis operations and is based on matrix algebra which is the algebraic manipulation of matrices or grid networks. See Map Algebra in the OceanTeacher Digital Library.
Working with NetCDF
NetCDF is a set of self-describing, machine-independent data formats that support the creation, access, and sharing of array-oriented scientific data. It is a file format for storing multidimensional scientific data (variables) such as temperature, humidity, pressure, wind speed, and direction.The project homepage is hosted by the Unidata program at the University Corporation for Atmospheric Research (UCAR). NetCDF is now being routinely used in some global remote sensing programs, for example the Group for High Resolution Sea Surface Temperature (GHRSST). GHRSST provides high quality sea surface temperature (SST) data for applications such as operational ocean and atmospheric forecasting systems to constrain the modelled upper ocean circulation thermal structure and for exchange of energy between the ocean and atmosphere.
GHRSST data products include:
Level 2 data products that provide satellite SST observations together with a measure of uncertainty for each observation in netCDF format. These data are ideal for data assimilation systems or as input to analysis systems.
Level 4 gridded products that are generated by combining complementary satellite and in situ observations within Optimal Interpolation systems. These data are ideal for model diagnostic studies, model boundary condition specification and model initialisation.
Plotting Vector Arrows from U and V Component Grids
QGIS can be used to generate motion vector arrows (also known as quiver or velocity plot) from U and V component grids for ocean currents and wind data to plot speed and direction vectors.
Marine Geospatial Ecology Tools (MGET). MGET is an open source geoprocessing toolbox designed for coastal and marine researchers and GIS analysts who work with spatial ecological and oceanographic data. MGET includes over 250 tools useful for a variety of tasks, such as downloading popular oceanographic datasets in GIS-compatible formats, identifying fronts and eddies in satellite images, building statistical habitat models from species observations and creating habitat maps, modeling biological connectivity by simulating hydrodynamic larval dispersal, and building grids that summarize fishing effort and other statistics. MGET includes a tool called Create Lines From Vector Component Rasters, which allows you to visualize current rasters or other vector fields with a shapefile that resembles a "quiver plot".
COADS monthly climatologies of Zonal and Meridional Wind can be used for gridding Zonal [U component or E-W vector] and Meridional [V component or N-S vector] Winds and Scalar Wind Speed. Read more about Scalars and Vectors in the OceanTeacher Digital Library.
Downloading species observations from the Ocean Biogeographic Information System (OBIS)
The Ocean Biogreographic information System (OBIS) provides a portal to datasets containing information on where and when marine species have been recorded. The datasets are integrated so you can search them all seamlessly by species name, higher taxonomic level, geographic area, depth, and time; and then map and find environmental data related to the locations. OBIS is part of the Intergovernmental Oceanographic Commission (IOC) of UNESCO, under its International Oceanographic Data and Information Exchange (IODE) programme.
KML is a file format used to display geographic data in an earth browser, such as Google Earth and Google Maps. A KML file specifies a set of features (place marks, images, polygons, 3D models, textual descriptions, etc.) for display in Google Earth and Google Maps, or any other geobrowser implementing the KML encoding. Each place always has a longitude and a latitude. Other attribute data can also be included. KML files are very often distributed in KMZ files, which are zipped files with a .kmz extension.
QGIS has the capability to create a map for printing or inclusion in another document using the Composer. The final map can include the map itself (which is the same as the data frame), a title, a legend, a scale, a north arrow, date of publication, and acknowledgements about data sources.