c. qgis - elearning.unipd.it

Silvia Elena Piovan, PhD – University of Padova, DiSSGeA GIS: Mapping and Analysis

GIS: Mapping and AnalysisDr. Silvia E. PiovanDepartment of Historical and Geographic Sciences and the Ancient World

University of Padova

[email protected]

C. QGIS


Primary GIS software concerns

• Computer Platform (Mac, Windows, Android)

• Cost (initial, options, support)

• Support (help, online, telephone)

• Reliability (software verified?)

• Supported data models/structures


QGIS and ArcGIS

• QGIS (Quantum GIS) is a free and open-source GIS application.

• Developed in early 2002 by Gary Sherman and then by the Open Source Geospatial Foundation in 2007.

• Version 1.0 was released in January 2009.

• QGIS integrates with other open-source GIS packages, including PostGIS, GRASS GIS, and MapServer.

• ArcGIS is a family of client software, server software, and online GIS services developed and maintained by

Environmental Systems Research Institute (Esri).

• ArcGIS Desktop version 8.0 dated back 1999.

• ArcGIS includes different applications, including ArcCatalog, ArcScene and ArcGlobe.

• It is neither free or open-source.

• Industry standard worldwide.

• Both QGIS and ArcGIS are used for viewing, editing, and analysis of geospatial data, creating and using maps,

sharing and discovering geographic information.

• They both lets you work with both vector and raster data models.


QGIS and ArcGISQGIS

ArcGIS

Analogies from QGIS to ArcGISBrowser CatalogLayers Table of Content


How set QGIS interface

• To change the QGIS interface from the default language (eg. Italian) to English:

• Impostazioni (Setting), Opzioni (Options), Generale (General).

• Pin "Sovrascrittura lingua del sistema" ("Override System Locale").

• Select "American English" from the menu "Traduzione Interfaccia Utente" (User Interface Translation").

• Select "Italian (it_IT)" from the menu "Localizzazione" ("Locale") and click "OK".


Structure of QGIS

• QGIS has two main windows:

• Main QGIS Window: To view, create, update, query, and analyze data.

• Layout QGIS Window: for the preparation of the layout map.

Main QGIS Window(to manage the project. In this example, the project is called "mapping_veneto")

The status bar shows the coordinates of the cursor, the scale of the canvas view and so on…


Structure of QGIS

• QGIS has two main windows:

• Main QGIS Window: To view, create, update, query, and analyze data.

• Layout QGIS Window: for the preparation of the layout map.

Layout QGIS Window(to manage the layout map of a project. In this example, the layout is called"Belluno" and it is a layout created from the project "mapping_veneto")

Here, the x and y coordinates for the image you are creating are shown: they are not referred to spatial coordinates (as geographic, UTM,…)!


Structure of QGIS

Toolbars

Browser ("Catalog" in ArcGIS)(to navigate and manage data, like to create new shapefile, add Open Street Map, …)

Map canvas (to visualize data – the "Data View" in ArcGIS)

Layers (to manage the list of layers in the project)

Spatial Coordinates

Scale

Main QGIS Window


Structure of QGIS

• In the Main Window, to organize toolbars and panels differently, click on View, Toolbars/Panels and check

the toolbars/panels that you prefer. Main QGIS Window


Structure of QGIS

Toolbars

The work-in-progress layout map

Lateral panels

Layout QGIS Window

X and Y Coordinates of the image


Structure of QGIS

• In the Layout Window, to organize toolbars and panels differently, click on View, Toolbars/Panels and check

the toolbars/panels that you prefer. Layout QGIS Window


Project

• A “Project” (also called “Map Document” in ArcGIS) can be considered the basic element for working with a

GIS (eg. QGIS). It can be seen as the “work table” of a given project, where all the layers can be shown and

managed.

• A QGIS project has the

extension.qgz.

• In ArcGIS, extension.mxd

• By setting a new project .qgz, you

can view, analyze, modify and map

the data that are present in that

project.

• When you start a new project, it is

a good practice to save it in a

specific folder (Project, Save as… ).


Setting CRS for the project

• When you start with a new project by clicking on "New Empty Project", by default it is set to the EPSG: 4326

- WGS84 Coordinate Reference System (CRS).


Setting CRS for the project

• It is important to set the Coordinate Reference System (CRS) you want to work with (Project, Properties,

CRS). If you know the CRS ID, you can filter using the code. Otherwise you need to search it on the

Predefined Coordinate Reference System list.

1.

2.3.

4.


Information Layers

• Add Layer

• It is possible to add layers to the Layers list (called Table Of Content – TOC in ArcGIS) clicking on Layer, Add Layer

and selecting the type of layer you want to add (eg.: a Vector Layer or a Raster Layer,…).


Information Layers

• Drag and drop from Browser

• To add layers, it is also possible to drag and drop the layer from the Browser.


Attribute Table

• To open the attribute table of a layer, right click on the layer, Open Attribute Table.


Attribute Table

• In the Attribute Table, you can perform a selection by pointing of records clicking on the side button (and

keep it press if selection more than one record, or use CTRL on keyboard).

Fields

Records


Attribute Table

• After having selected one or more records, it is possible to zoom on them, using Zoom map to the selected

rows on the Attribute Table toolbar. The selected features will be enlighted in yellow (you can change this

default setting in Project, Properties…, General).


Attribute Table

• It is possible to order the records (ascending/descending) clicking on the little arrow on the right side of the

field name.


Datasource issue

• Once you have saved and closed your project, remember that if you change the name of the layers or their

location in the computer, the next time that you will open the project, the system will give you the warning.

This is due to the fact that the system is not able to find the right Datasource anymore.To solve the issue, just click on Browse and set the current source for the data.

c. qgis - elearning.unipd.it

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