2. What is a Geographic Information System
Definitions
• A geographic information system (GIS) integrates hardware,
software, and data for capturing, managing, analyzing, and
displaying all forms of geographically referenced information.
• GIS allows us to view, understand, question, interpret, and visualize
data in many ways that reveal relationships, patterns, and trends in
the form of maps, globes, reports, and charts
3. What is a Geographic Information System
Hardware
• GPS handsets
• Digitizing tables to digitize topographic maps and charts
• Plotters and printers
Software
• ArcGIS (ESRI, commercial)
• MapInfo (Pitner Bowes Software, commercial)
• Quantum GIS (open source)
4. QGIS vs ArcGIS
• QGIS and ArcGIS desktop have similar features
• ArcGIS is commercial, well documented and supported
• QGIS is open source and free, extended with plugins, very active community
• ArcGIS is usually favoured by large companies such as utilities who can afford
licencing and training costs
• QGIS is favoured by GIS enthusiasts, students, small companies
What is a Geographic Information System
5. What is a Geographic Information System
Data
• Topographic maps
• Toponyms
• Nautical charts
• Bathymetric charts
• Geomorphological classification
• Aerial and satellite imagery
• Field data
6. Topographic maps
• Generally produced by the Lands and Surveys from topographic surveys and aerial
photography
• Show relief, vegetation, water, buildings and relief features
• Legacy maps are often in paper form, use diverse projections/datum and are not
always readily usable in GIS software.
7. Toponyms
• Toponyms are geographic names, gathered from old paper maps and charts or
provided by Lands & Surveys
• GeoNames (http://www.geonames.org) is a global geographic database that provides
a geographic index of more than 11 million geographic names (gazetteer)
• An approximate location is associated to place names
• A: administrative areas, country, state, region,...
• H: hydrographic features, bay, channel, stream, lake
• L: land features, parks,area,...
• P: populated places, city, village,...
• R: road, railroad ,…
• S: spot, building, farm,…
• T: island, mountain, peak, hill,rock,...
• U: undersea, trench seamount, shoal,…
• V: forest,coconut grove, bush,…
Name Alternate names Latitude Longitude Feature
class
Feature
code
Eua 'Eua, ai wa dao,e-
ua seom, エウア島,
埃瓦島,에우아 섬 -21.3632 -174.93 A ADM1
Vai’utukakau -18.5957 -173.926 H BAY
Fa‘onelua Tropical Garden -21.1371 -175.226 L PRK
Tefisi Ngaakau,Tefisi -18.6298 -174.014 P PPL
Tonga College `Atele,‘Atele -21.1842 -175.226 S SCHC
Tufaka Island Tufagga -21.067 -175.254 T ISL
Feinga Seamount -20.15 -175.15 U SMU
11. Maritime boundaries
Maritime boundaries encompass the Exclusive Economic Zone (EEZ), territorial seas (12
nm), contiguous zones (24 nm), internal waters and archipelagic waters.
Latest maritime boundaries can be obtained from http://www.marineregions.org
Capricorn Seamount
12. Nautical charts
• Nautical charts are produced by the hydrographic offices for navigation purpose
• It details coastline, soundings, underwater features, navigation aids and hazards
• Legacy charts are often in paper form, use diverse projections/datum and are not
always readily usable in GIS software
13. Bathymetric charts
Bathymetric charts are produced by the hydrographic offices after conducting
bathymetric surveys of the seafloor but actual data is scarce.
Capricorn Seamount
14. LiDAR data
LiDAR is a surveying method that measures distance to the plane using laser pulses.
Bathymetric LiDAR can measure depth up to 50 m by using green lasers. That data is
scarce in Pacific countries, and bathymetric LiDAR even rarer.
LiDAR derived information can be used as part of habitat mapping (shallow reefs,
mangroves)
Capricorn Seamount
15. Satellite imagery
Low resolution satellite imagery is generally available for free, while high-resolution
imagery must be purchased and licensing usually restrict its distribution
Freely available low resolution multi-spectral & radar satellite imagery
• Landsat 7 ETM+, Landsat 8… : Earth Explorer (http://earthexplorer.usgs.gov)
• Sentinel-1,2,3 : Copernicus Open Access Hub (https://scihub.copernicus.eu)
Ocean monitoring
• Sea Surface Temperature, Chlorophyll-a (SeaWIFS), MODIS : NOAA/NASA
(https://oceancolor.gsfc.nasa.gov)
Commercial high-resolution imagery
• IKONOS, GeoEye, QuickBird, WorldView-1,2,3,4
Pléiades,…
Capricorn Seamount
16. Aerial photography
Aerial photography has a higher resolution than satellite imagery but requires flying a
survey plane above the area. Survey drones (fixed-wings) can also be used for small
areas (a few ha)
Legacy aerial surveys were using rolls of films, that needed to be scanned and the
imagery rectified. Nowadays aerial surveys use multispectral sensors similar to satellites.
Capricorn Seamount
17. What is a Geographic Information System
Definitions
• A geographic information system (GIS) integrates hardware, software, and data for
capturing, managing, analyzing, and displaying all forms of geographically
referenced information.
• GIS allows us to view, understand, question, interpret, and visualize data in many
ways that reveal relationships, patterns, and trends in the form of maps, globes,
reports, and charts (source: www.gis.com)
21. Layer types
Raster Layer
A raster layer is an image (scanned picture, satellite image).
Common image formats used in GIS are
• GeoTIFF (*.TIF)
• ERDAS Compress Wavelets (*.ECW)
• JPEG 2000 (*.JP2)
• ESRI HDR (*.BIL)
• Binary Grid (*.GRD) for bathymetry and
elevations
High Res (World View 2)
Low Res (Landsat 7)
22. Layer types
Vector Layer
A vector layer consists in geometrical primitives such as points, lines, polylines and
polygons to which can be associated attributes (name, value etc….)
Common vector formats used in GIS are
• ESRI Shapefile (*.SHP)
• MapInfo TAB (*.TAB)
• Keyhole Markup Language (*.KML)
• GPS eXchange Format (*.GPX)
Vector layers can be manipulated and zoomed-in to any arbitrary resolution.
23. Layer types
Delimited Text Layer
Text file with columns separated by a delimiter (often tab, colon or semicolon)
Often used to import field data with GPS position into the GIS.
• Must contain columns with longitude and latitude in decimal degrees
• Coordinate reference system is WGS 84 / ESPG:4326
