QGIS TRAINING Introduction to GIS What is a

QGIS TRAINING Introduction to GIS

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

What is a Geographic Information System Hardware • • • GPS handsets Digitizing tables to digitize topographic maps and charts Plotters and printers Software • • • Arc. GIS (ESRI, commercial) Map. Info (Pitner Bowes Software, commercial) Quantum GIS (open source)

What is a Geographic Information System QGIS vs Arc. GIS • • • QGIS and Arc. GIS desktop have similar features Arc. GIS is commercial, well documented and supported QGIS is open source and free, extended with plugins, very active community • Arc. GIS 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 Data • • Topographic maps Toponyms Nautical charts Bathymetric charts Geomorphological classification Aerial and satellite imagery Field data

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.

Toponyms • Toponyms are geographic names, gathered from old paper maps and charts or provided by Lands & Surveys Geo. Names (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, . . . Name Alternate names Latitude Longitude P: populated places, city, village, . . . Eua 'Eua, ai wa dao, e. R: road, railroad , … ua seom, エウア S: spot, building, farm, … 島, 埃瓦島, 에우아 -21. 3632 -174. 93 섬 T: island, mountain, peak, hill, rock, . . . Vai’utukakau -18. 5957 -173. 926 U: undersea, trench seamount, shoal, … Fa‘onelua Tropical Garden -21. 1371 -175. 226 Tefisi Ngaakau, Tefisi -18. 6298 -174. 014 V: forest, coconut grove, bush, … • • Tonga College Tufaka Island Feinga Seamount `Atele, ‘Atele Tufagga -21. 1842 -175. 226 -21. 067 -175. 254 -20. 15 -175. 15 Feature class A H L P S T U Feature code ADM 1 BAY PRK PPL SCHC ISL SMU

Feature class Toponyms T: island, mountain, peak, hill, rock, … Feature class H: hydrographic features, bay, channel, stream, lake, …

Feature class Toponyms P: populated places, city, village 50 72 0 m

Toponyms Feature class Feature codes

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

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

Bathymetric charts are produced by the hydrographic offices after conducting bathymetric surveys of the seafloor but actual data is scarce. Capricorn Seamount

Li. DAR data Li. DAR is a surveying method that measures distance to the plane using laser pulses. Bathymetric Li. DAR can measure depth up to 50 m by using green lasers. That data is scarce in Pacific countries, and bathymetric Li. DAR even rarer. Li. DAR derived information can be used as part of habitat mapping (shallow reefs, mangroves) Capricorn Seamount

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 (Sea. WIFS), MODIS : NOAA/NASA (https: //oceancolor. gsfc. nasa. gov) Commercial high-resolution imagery • IKONOS, Geo. Eye, Quick. Bird, World. View-1, 2, 3, 4 Pléiades, … Capricorn Seamount

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

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)

Visualizing spatial data

Manipulating spatial data

Visualizing layers in a GIS

Layer types Raster Layer A raster layer is an image (scanned picture, satellite image). Common image formats used in GIS are • • • Geo. TIFF (*. TIF) ERDAS Compress Wavelets (*. ECW) JPEG 2000 (*. JP 2) ESRI HDR (*. BIL) Binary Grid (*. GRD) for bathymetry and elevations Low Res (Landsat 7) High Res (World View 2)

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) • Map. Info TAB (*. TAB) • Keyhole Markup Language (*. KML) • GPS e. Xchange Format (*. GPX) Vector layers can be manipulated and zoomed-in to any arbitrary resolution.

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

Layer types

Layer attributes (vector) Data associated with points, lines and polygons

Layer style (vector) Colors, shapes and sizes for the layer

Layer style (raster) Manipulation of the raster image

QGIS Latest version of QGIS can be obtained from https: //www. qgis. org

QGIS 3. 6