diff --git a/doc/conf.py b/doc/conf.py index 78910b99..7bb1e03f 100644 --- a/doc/conf.py +++ b/doc/conf.py @@ -187,3 +187,10 @@ def linkcode_resolve(domain, info): extlinks = { "github": ("https://github.com/nsidc/qgreenland/tree/main/%s", "GitHub: %s"), } + +# -- Options for figures ------------------------------------------------------ +# https://www.sphinx-doc.org/en/master/usage/configuration.html#confval-numfig: +# > If true, figures, tables and code-blocks are automatically numbered if +# > they have a caption. The numref role is enabled. Obeyed so far only by +# > HTML and LaTeX builders. +numfig = True diff --git a/doc/disclaimer.md b/doc/disclaimer.md index 34e485c0..ede1a91c 100644 --- a/doc/disclaimer.md +++ b/doc/disclaimer.md @@ -16,6 +16,6 @@ the best approximation reference layer for geolocating Greenland's coastline. Note that some data were transformed from their native data formats, projections, and resolutions for inclusion within QGreenland. The included -metadata (>Layer Properties >Metadata >History) contains provenance information +metadata (**Layer Properties -> Metadata -> History**) contains provenance information on any transformations. All QGreenland GeoPackages and GeoTIFFs are projected in `EPSG:3413`. diff --git a/doc/user/tutorials/analyze-ice-sheet-volume.md b/doc/user/tutorials/analyze-ice-sheet-volume.md index 3fd49621..f5f5ebe4 100644 --- a/doc/user/tutorials/analyze-ice-sheet-volume.md +++ b/doc/user/tutorials/analyze-ice-sheet-volume.md @@ -1,3 +1,4 @@ +(calculate-volume-greenland-ice-sheet-tutorial)= # Calculate the volume of the Greenland ice sheet The **Processing Toolbox** in QGIS provides a collection of tools and @@ -22,8 +23,8 @@ first ## Open the Processing Toolbox -The **Processing Toolbox** can be opened from the menu bar by selecting -**"View>Panels>Processing Toolbox"**. This will open a new panel with a variety of +The **Processing Toolbox** can be opened from the menu bar by selecting **View +-> Panels -> Processing Toolbox**. This will open a new panel with a variety of processing tools organized into groups. ![processing_toolbox](/_images/processing_toolbox.jpg) @@ -36,9 +37,9 @@ Toolbar** ![attributes-toolbar](/_images/attributes-toolbar.jpg). ## Use the Raster Surface Volume tool -In the **Processing Toolbox**, go to **"Raster analysis > Raster surface volume"**. This -is an algorithm that calculates the volume under a raster grid’s -surface. Double-click **"Raster surface volume"** to open the tool's window, and +In the **Processing Toolbox**, go to **Raster analysis -> Raster surface +volume**. This is an algorithm that calculates the volume under a raster grid’s +surface. Double-click **Raster surface volume** to open the tool's window, and enter the following parameters: * **Input layer** = Ice thickness (150 m) @@ -52,26 +53,26 @@ enter the following parameters: ![raster_surface_volume](/_images/raster_surface_volume.jpg) -Click "Run" and wait for the analysis to finish. The window will switch to the -"Log" tab, which shows log messages and results for the run. A **Results +Click **Run** and wait for the analysis to finish. The window will switch to the +**Log** tab, which shows log messages and results for the run. A **Results Viewer** panel should open in a panel underneath the **Processing -Toolbox**. Close the Raster surface volume tool's window and click on the +Toolbox**. Close the **Raster surface volume** tool's window and click on the "Surface volume report" entry in the **Results Viewer**. This will show a link to a results HTML page that can be opened in your broswer. Open this file and review the results. ![results_viewer](/_images/results_viewer.jpg) -The **results file** will contain information from the run, including which file was +The results file will contain information from the run, including which file was analyzed, the calculated volume, pixel count, and total area. If one has succuessfully run the analysis, the results should show that the Greenland ice -sheet has a volume of 2,942,360,633,311,806 m3, or about 2.9 million +sheet has a volume of 2,965,561,810,382,715 m3, or about 3 million km3. ## Summary In completing this tutorial, the user has become familar with the **Processing -Toolbox** and has successfully utilized the Raster Surface Volume tool with ice +Toolbox** and has successfully utilized the **Raster Surface Volume** tool with ice sheet thickness data included in the QGreenland core package to calculate the volume of the Greenland ice sheet. Having accomplished this, the user is now ready to explore other geospatial processing tools included in the **Processing diff --git a/doc/user/tutorials/create-print-layout.md b/doc/user/tutorials/create-print-layout.md index 24471620..8ca1b614 100644 --- a/doc/user/tutorials/create-print-layout.md +++ b/doc/user/tutorials/create-print-layout.md @@ -12,9 +12,9 @@ for complete documentation on print layouts in QGIS. ## Creating a new print layout -Once one has created a map in the **QGIS map display** that one would like to print -or publish, one needs to switch to the **QGIS print layout**. Select **"Print Layout"** -from the "Project" menu. +Once one has created a map in the QGIS **Map View** that one would like to print +or publish, one needs to switch to the QGIS **Print Layout**. From the menu bar, +select **Project -> Print Layout**. ```{note} The **Project Toolbar** ![project_toolbar](/_images/project_toolbar.jpg) also @@ -23,7 +23,7 @@ that creates a new **Print Layout**. ``` First, name the new print layout after the figure you plan to create and click -**"OK"**. +**OK**. ![print_layout_name](/_images/print_layout_name.jpg) @@ -34,7 +34,7 @@ When the print layout window opens, it will be initially blank. ## Changing the print layout's properties To change the size and orientation of your print layout, right click in the map -area and choose **"Page Properties"**. This will add page size options to the **Item +area and choose **Page Properties**. This will add page size options to the **Item Properties** panel on the right side of the screen. ![print_page_properties](/_images/print_page_properties.jpg) @@ -58,8 +58,8 @@ possible to manipulate the map area within the box. Now explore some of the other buttons included in the map layout Toolbar. Add a north arrow and scale bar. Finally, once one is happy with the layout, try -exporting the layout as an image by opening the **"Layout"** menu and selecting -**"Export as Image"**. +exporting the layout as an image by opening the **Layout** menu and selecting +**Export as Image**. ## Summary diff --git a/doc/user/tutorials/get-started.md b/doc/user/tutorials/get-started.md index ff66c8be..ea9bde75 100644 --- a/doc/user/tutorials/get-started.md +++ b/doc/user/tutorials/get-started.md @@ -52,7 +52,7 @@ version of QGIS. ```{note} If QGIS is already open, one can open the `qgreenland.qgs` project file -within QGIS by navigating to the **"Project >Open..."** option in the menu bar and +within QGIS by navigating to the **Project -> Open...** option in the menu bar and selecting the `qgreenland.qgs` file from its saved location. ``` @@ -67,8 +67,14 @@ are using, your QGIS interface may look slightly different. The main components of the QGIS interface are the **Map view**, **Status bar**, **Layers panel**, **Toolbars**, and the **Menu bar**. -![map_view](/_images/map_view.jpg) -Fig. 1: Main components of the QGIS/QGreenland interface + +```{figure} /_images/map_view.jpg +--- +alt: Map View +name: map_view +--- +Main components of the QGIS/QGreenland interface. +``` The **Map View** is the main part of the QGIS/QGreenland Core interface where the data layers are displayed. A GIS ‘layer’ refers to a geospatial dataset along with the symbols and labels used @@ -87,25 +93,67 @@ vice versa. Layers can be manually moved around in the **Layers Panel** to chang the order in which they show up. **Panels** and **Toolbars** can also be manually moved around the QGIS interface to fit the user’s preferences. -When you first open the QGreenland Core data package, two reference layers will be automatically toggled on: Greenland coastlines 2017 and the QGreenland Basemap. Layers can be rearranged by clicking and dragging up or down. Layer groups can be expanded or collapsed by clicking on the arrow to the left of the checkbox. To expand or collapse all layers at once, click on the respective buttons (Fig. 2 (a)) right above the layers list in the **Layers Panel**. In addition to the **Layers Panel**, there are a variety of other panels that can be displayed on the QGIS interface. For example, the Browser panel provides a shortcut for accessing other data layers or project files on your computer or another location. Panels can be moved around the interface by clicking and dragging, and can be removed by clicking on the ‘X’ box in the upper righthand corner. - -![QGIS_fig2](/_images/QGIS_fig2.png) - -Fig. 2: (a) Buttons above **Layers Panel** to expand or collapse layers; (b) hand button to grab and drag the map view; (c) magnifying glass buttons to zoom in or out in map view; (d) Zoom Full button to bring all visible layers into **Map View**; (d) Zoom to Layer button to bring a desired layer into view. - -The **Toolbars** contain buttons that allow the user to interact with the **Map View**. For example, the hand button (Fig. 2 (b)) in the **Map Navigation Toolbar** lets the user grab and drag the map view around. The magnifying glass buttons (Fig. 2 (c)) allow the user to zoom in and out or to a particular feature or -selection in the map view. More information about a toolbar button’s function can be obtained by hovering one’s mouse over the button. **Toolbars** can be moved around the QGIS workspace by clicking and dragging. To toggle a toolbar on or off, simple right click on a toolbar and check or uncheck the desired boxes. (Fig. 3). - -If data layers are toggled on but not visible in the map view, the magnifying glass with three arrows (‘Zoom Full’) button (Fig. 2 (d)) will bring all visible layers back into the map view. -Right clicking on a layer in the **Layers Panel** and selecting ‘Zoom to Layer’ or clicking on the magnifying glass over a square button (Fig. 2 (e)) in the **Map Navigation Toolbar** will also bring a desired layer into view in the **Map View**. +When you first open the QGreenland Core data package, two reference layers will +be automatically toggled on: Greenland coastlines 2017 and the QGreenland +Basemap. Layers can be rearranged by clicking and dragging up or down. Layer +groups can be expanded or collapsed by clicking on the arrow to the left of the +checkbox. To expand or collapse all layers at once, click on the respective +buttons ({numref}`qgis_buttons` (a)) right above the layers list in the **Layers +Panel**. In addition to the **Layers Panel**, there are a variety of other +panels that can be displayed on the QGIS interface. For example, the **Browser +Panel** provides a shortcut for accessing other data layers or project files on +your computer or another location. Panels can be moved around the interface by +clicking and dragging, and can be removed by clicking on the ‘X’ box in the +upper righthand corner. + + +```{figure} /_images/QGIS_fig2.png +--- +alt: QGIS buttons +name: qgis_buttons +--- +(a) **Expand All** and **Collapse All** buttons at the top of the **Layers +Panel** to expand or collapse layers; (b) **Pan Map** button in the **Map +Navigation Toolbar** to grab and drag the map view; (c) **Zoom In** and **Zoom +Out** buttons in the **Map Navigation Toolbar** to zoom in or out in map view; +(d) **Zoom Full** button in the **Map Navigation Toolbar** to bring all visible +layers into the **Map View**; (d) **Zoom to Layer** button in the **Map +Navigation Toolbar** to bring a desired layer into view. +``` -![QGIS_figure3](/_images/QGIS_figure3.png) -Fig. 3: **Toolbars** can be added or removed by right clicking on the toolbar area and checking/unchecking boxes. +The **Toolbars** contain buttons that allow the user to interact with the **Map +View**. For example, the **Pan Map** button ({numref}`qgis_buttons` (b)) in the +**Map Navigation Toolbar** lets the user grab and drag the map view around. The +magnifying glass buttons ({numref}`qgis_buttons` (c)) allow the user to zoom in +and out or to a particular feature or selection in the map view. More +information about a toolbar button’s function can be obtained by hovering one’s +mouse over the button. **Toolbars** can be moved around the QGIS workspace by +clicking and dragging. To toggle a toolbar on or off, simple right click on a +toolbar and check or uncheck the desired boxes ({numref}`qgis_toolbars`). + +If data layers are toggled on but not visible in the map view, the magnifying +glass with three arrows (**Zoom Full**) button ({numref}`qgis_buttons` (d)) will +bring all visible layers back into the map view. Right clicking on a layer in +the **Layers Panel** and selecting **Zoom to Layer** or clicking on the +magnifying glass over a square button ({numref}`qgis_buttons` (e)) in the **Map +Navigation Toolbar** will also bring a desired layer into view in the **Map +View**. + + +```{figure} /_images/QGIS_figure3.png +--- +alt: QGIS Toolbars +name: qgis_toolbars +--- +**Toolbars** can be added or removed by right clicking on the toolbar area and checking/unchecking boxes. +``` -Lastly, the **Menu bar** and **Toolbars** are different ways to access most QGIS functions, such -as opening or saving a project or analyzing the data using geoprocessing -tools. **Panels** are another way for users to interact with data layers and -functions in QGIS. You can fully customize the look and layout of your QGIS interface by going to ‘View’ in the menu bar and selecting the **Panels**, **Toolbars**, etc. that you would like visible. +Lastly, the **Menu bar** and **Toolbars** are different ways to access most QGIS +functions, such as opening or saving a project or analyzing the data using +geoprocessing tools. **Panels** are another way for users to interact with data +layers and functions in QGIS. You can fully customize the look and layout of +your QGIS interface by going to ‘View’ in the menu bar and selecting the +**Panels**, **Toolbars**, etc. that you would like visible. ```{note} @@ -120,9 +168,10 @@ GIS](https://docs.qgis.org/3.28/en/docs/gentle_gis_introduction/index.html) ## 4) Browse data in the QGreenland project -Layers in QGreenland Core are organized into groups by category. For example, the -"Background boundary" layer is "QGreenland boundaries" group, which is itself -inside of the "Reference" group ("Background boundary/Reference"). +Layers in QGreenland Core are organized into groups by category. For example, +the "Background boundary" layer is "QGreenland boundaries" group, which is +itself inside of the "Reference" group ("Reference/QGreenland +boundaries/Background boundary"). ![layer_groups](/_images/layer_groups.jpg) @@ -133,8 +182,8 @@ visualize another data layer (or remove an existing one), toggle the checkbox next to the layer in the **Layers panel**. Toggle on the "Ice thickness (150m)" layer, which is in the "Terrain -models/Bedmachine" group. The **Map view** should now include a visualization of -Ice thickness at a 150m spatial resolution. +models/Bedmachine v5" group. The **Map view** should now include a visualization +of Ice thickness at a 150m spatial resolution. ![ice_thickness_displayed](/_images/ice_thickness_displayed.jpg) diff --git a/doc/user/tutorials/interacting-with-geospatial-data.md b/doc/user/tutorials/interacting-with-geospatial-data.md index efa72e3c..76153c9a 100644 --- a/doc/user/tutorials/interacting-with-geospatial-data.md +++ b/doc/user/tutorials/interacting-with-geospatial-data.md @@ -1,5 +1,10 @@ # Interacting with Geospatial Data in QGreenland Core +```{note} +QGreenland users will learn through experience that there is very often more than +one way to complete a desired task in the QGIS platform +``` + ## Spatial Data Overview There are two main basic kinds of GIS data layers: vector and raster. @@ -7,57 +12,66 @@ There are two main basic kinds of GIS data layers: vector and raster. ### Vector Data -**Vector** data are composed of points, lines, and polygons and represent discrete features. +Vector data are composed of points, lines, and polygons and represent discrete features. Examples of vector data are cities (points), roads and highways (lines), and geographic -boundaries like country borders (polygons) (Fig. 4). All of the vector layers in QGreenland are +boundaries like country borders (polygons) ({numref}`vector_data`). All of the vector layers in QGreenland are GeoPackage (.gpkg) files. A GeoPackage is just a platform-independent file type for storing geospatial data. -![vector_data](/_images/vector_data.png) - -Fig. 4: Examples of **Vector** data layers in QGreenland Core: Points (towns and settlements), lines +```{figure} /_images/vector_data.png +--- +alt: Vector data +name: vector_data +--- +Examples of vector data layers in QGreenland Core: points (towns and settlements), lines (median January sea ice extent), and polygons (country boundaries). +``` -### Vector Data Attributes +#### Vector Data Attributes All QGIS vector data layers have associated attributes, or characteristics of the discrete features. Attributes can be almost anything: city name, road type (highway, paved, unpaved, etc.), land elevation value, population density, date, etc. The attributes of a data layer can be -viewed in tabular form by right clicking on the layer in the **Layers Panel** and selecting ‘Open -Attribute Table’ from the menu options, or by clicking on the layer in the **Layers Panel** and -then clicking on the Open Attribute Table button in the **Attributes Toolbar**. This opens +viewed in tabular form by right clicking on the layer in the **Layers Panel** and selecting **Open +Attribute Table** from the menu options, or by clicking on the layer in the **Layers Panel** and +then clicking on the **Open Attribute Table** button in the **Attributes Toolbar**. This opens up an **Attribute Table**, where the columns are the various fields, or attributes, and the rows are individual features. Clicking on and highlighting records in the **Attribute Table** will also highlight those specific points, lines, or polygons in the **Map View**. Right-click any cell to -‘Zoom to feature’, ‘Pan to feature’, or ‘Flash feature’. +**Zoom to feature**, **Pan to feature**, or **Flash feature**. ### Raster Data -**Raster** data are composed of grid cells or pixels, where each grid cell has its own value. +Raster data are composed of grid cells or pixels, where each grid cell has its own value. Rasters represent continuous data, such as land elevation, surface temperature, land cover, -etc. (Fig. 5). The resolution, which is the length of the grid cell sides of each raster dataset in -QGreenland, is indicated in the name of the dataset, e.g.: “Ice Sheet Velocity (500 m)”. **Raster** +etc. ({numref}`raster_data`). The resolution, which is the length of the grid cell sides of each raster dataset in +QGreenland, is indicated in the name of the dataset, e.g.: “Ice Sheet Velocity (500 m)”. Raster layers in QGreenland are all GeoTIFF files, which are images with geographic features, such as geospatial metadata and overviews/tile pyramids. -![raster_data](/_images/raster_data.png) - -Fig. 5: Example of a **Raster** data layer in QGreenland, ice sheet velocity, where +```{figure} /_images/raster_data.png +--- +alt: Raster data +name: raster_data +--- +Example of a Raster data layer in QGreenland, ice sheet velocity, where each grid cell in the raster is 500 m x 500 m and is color-coded by a velocity - +``` (interacting-with-geospatial-data-layer-properties)= ## Layer Properties -Right clicking on a data layer in the **Layers Panel** and selecting ‘Properties’, or simply double -clicking on a layer in the Layers panel will bring up the **Layer Properties** dialog window, -which contains a variety of information about a layer (Fig. 6). The information is organized -into sections (or tabs) that can be accessed by clicking on an individual tab (e.g., Symbology) -in the left sidebar of the window. The tabs listed in a vector **Layer Properties** dialog window -differ slightly from those listed for a **Raster** layer. The tabs most relevant to a novice QGIS user -and that exist for both **Vector** and **Raster** layers are: +Right clicking on a data layer in the **Layers Panel** and selecting +**Properties**, or simply double clicking on a layer in the **Layers panel** +will bring up the **Layer Properties** dialog window, which contains a variety +of information about a layer ({numref}`layer_properties`). The information is +organized into sections (or tabs) that can be accessed by clicking on an +individual tab (e.g., **Symbology**) in the left sidebar of the window. The tabs +listed in a vector **Layer Properties** dialog window differ slightly from those +listed for a raster layer. The tabs most relevant to a novice QGIS user and that +exist for both vector and raster layers are: * **Information**: This section summarizes information about a layer, including its name, coordinate reference system, spatial extent (geographic boundaries), description (abstract), and more. @@ -72,32 +86,38 @@ thus simply copy a layer’s citation directly from its metadata. An abbreviated metadata can also be viewed by selecting a layer in the Layers panel and hovering your mouse over the layer name. -**Note**: The QGreenland team has in a few instances included comments on ‘Noted +```{note} +The QGreenland team has in a few instances included comments on ‘Noted Data Issues’. Read about ‘Noted Data Issues’ in the layer metadata. These are currently noted for the ‘Populated places’ layer. Regardless, QGreenland makes no guarantees about the accuracy and validity of data contained in -QGreenland. - -![layer_properties](/_images/layer_properties.png) - -Fig. 6: The **Layer Properties** dialog window for the QGreenland ‘Earthquakes’ data layer - - -## Data Projections - -Data projections, or Coordinate Reference Systems (CRS), define the coordinate system for -a QGIS project and data layers. The CRS for the current **Map View** is indicated on the right -side of the QGIS status bar. For QGreenland, the current CRS should be identified as ‘EPSG: -3413,’ which is the identifier for the NSIDC Sea Ice Polar Stereographic North on a WGS 84 -Ellipsoid CRS. Changing the CRS of the **Map View** will not change the underlying data, -though QGIS will do on-the-fly reprojection of layers not in the selected CRS. It is -possible to reproject a layer into a new CRS; however, this transforms the data and can -introduce artifacts. Therefore, it is recommended that to reproject data, the user do so -from the source data and not the data contained in the QGreenland package. - +QGreenland. See our [Disclaimer](/disclaimer.md) for more information. +``` + +```{figure} /_images/layer_properties.png +--- +alt: Layer Properties +name: layer_properties +--- +The **Layer Properties** dialog window for the QGreenland ‘Earthquakes’ data layer. +``` + +## Coordinate Reference System (CRS) + +Coordinate Reference Systems (CRS), define the coordinate +system for a QGIS project and data layers. The CRS for the current **Map View** +is indicated on the right side of the QGIS status bar. For QGreenland, the +current CRS should be identified as `EPSG: 3413`, which is the identifier for +the NSIDC Sea Ice Polar Stereographic North on a WGS 84 Ellipsoid CRS. Changing +the CRS of the **Map View** will not change the underlying data, though QGIS +will do on-the-fly reprojection of layers not in the selected CRS. It is +possible to reproject a layer into a new CRS; however, this transforms the data +and can introduce artifacts. Therefore, it is recommended that to reproject +data, the user do so from the source data and not the data contained in the +QGreenland package. (scale-dependent-rendering)= -### Scale-Dependent Rendering +## Scale-Dependent Rendering Scale-dependent rendering refers to the scale at which a particular data layer will be visible in the QGIS map display. This can make it easier to zoom in and out for certain data layers. The @@ -106,21 +126,26 @@ Rendering**, checking the box for Scale Dependent Visibility, and then setting t and maximum scale dependent visibility. For scale reference, refer to the scale indicated at the bottom of the QGIS interface in the **Status Bar**. +## QGreenland Data Layers -### QGreenland Data Layers A complete list of all QGreenland data layers and their metadata, including information about -their original data source, can be found in the layer_list.csv file included in the QGreenland +their original data source, can be found in the `layer_list.csv` file included in the QGreenland download package. ## Identifying Features in Layers -One of the most basic ways to interact with data in QGIS is to use the **Identify Features** -button in the **Attributes Toolbar** to quickly view the attributes of an individual record (i.e., a -single point, line, or polygon in a **Vector Layer** or a single cell in a **Raster Layer**). **Note**: If you do -not see this button in any of your **Toolbars**, then you need to toggle on the **Attributes Toolbar**. -Either right click anywhere in the **Toolbar** area and check the box next to **Attributes Toolbar**, -or go to **View -> Toolbars** in the **Menu Bar**. +One of the most basic ways to interact with data in QGIS is to use the +**Identify Features** button in the **Attributes Toolbar** to quickly view the +attributes of an individual record (i.e., a single point, line, or polygon in a +vector layer or a single cell in a raster layer). + +```{note} +If you do not see the **Identify Features** button in any of your **Toolbars**, then you need to +toggle on the **Attributes Toolbar**. Either right click anywhere in the +**Toolbar** area and check the box next to **Attributes Toolbar**, or go to +**View -> Toolbars** in the **Menu Bar**. +``` To use the **Identify Features** button: 1. First, make sure that the layer (not just layer group) that you are interested in @@ -129,20 +154,25 @@ To use the **Identify Features** button: 2. Click on the **Identify Features** button in the **Attributes Toolbar**. 3. Click on the individual point, line, polygon, or raster cell of interest in the map view. The record for the object selected will show up in a new **Identify Results Panel** - to the right of the map display (Fig. 7). + to the right of the map display ({numref}`identify_results_panel`). 4. You can choose what information the **Identify** tool is showing you and how it is displayed by toggling the **Mode** and **View** options at the bottom of the **Identify Results Panel**. -![identify_results_panel](/_images/identify_results_panel.png) - -Fig. 7: The **Identify Results Panel** that shows results from the **Identify Features** tool. +```{figure} /_images/identify_results_panel.png +--- +alt: Identify results panel +name: identify_results_panel +--- +The **Identify Results Panel** that shows results from the **Identify Features** tool. +``` ## Measuring Distances, Areas, and Angles -Another useful basic tool in the **Attributes Toolbar** is the **Measuring Tool**. The **Measuring Tool** -is a quick and easy way to measure distances between two points or along a line, area of -a polygon, or angles between geographic features or locations. +Another useful basic tool in the **Attributes Toolbar** is the **Measuring +Tool**. The **Measuring Tool** is a quick and easy way to measure distances +between two points or along a line, area of a polygon, or angles between +geographic features or locations. To use the **Measuring Tool**: 1. Click on the arrow to the right of the **Measuring Tool** button and choose if you @@ -167,8 +197,8 @@ To use the **Measuring Tool**: ## Adding Text Annotations to the Map View -You can add a text annotation anywhere in the **Map View** using the text annotation tool -in the **Attributes Toolbar**. +You can add a text annotation anywhere in the **Map View** using the text +annotation tool in the **Attributes Toolbar**. To use the **Text Annotation Tool**: 1. Click on the text annotation button in the **Attributes Toolbar**. @@ -177,7 +207,7 @@ To use the **Text Annotation Tool**: 3. Double click on the box to open a new window where you can write your annotation and choose the font you want to use, among other things (e.g., you can link the annotation to a specific layer). -4. When you’re done, click **Apply** and then **Ok** to close the window. +4. When you are done, click **Apply** and then **Ok** to close the window. 5. To delete an annotation, double click on it to open the dialog window, then click **Delete**. @@ -190,10 +220,10 @@ in the **Map View**). To modify a layer’s symbology: 1. Open the **Layer Properties** dialog window for the layer you want to edit. 2. Go to the **Symbology** section and modify the layer symbology as desired. - a) For a **Vector Layer**, you can choose from a built-in set of QGIS symbols, and/ + a) For a vector layer, you can choose from a built-in set of QGIS symbols, and/ or can change individual characteristics of the layer’s symbology such as symbol shape, weight, color, size, opacity, and more. - b) For a **Raster Layer**, you can change the color properties of the grid cells, as + b) For a raster layer, you can change the color properties of the grid cells, as well as characteristics like brightness and contrast. The opacity/transparency of a raster layer can be changed in the **Transparency** tab of the **Layer Properties** dialog window. @@ -202,9 +232,9 @@ To modify a layer’s symbology: ## Processing Toolbox The **Processing Toolbox** is what makes the QGIS platform a powerful spatial data analysis tool. -The **Toolbox** is a collection of tools and prewritten algorithms that allow the user to perform a -wide variety of **Raster and Vector** data analyses. For example, the **Processing Toolbox** contains -tools for identifying features in a **Vector Layer** that fulfill certain criteria, extracting selected +The **Processing Toolbox** is a collection of tools and prewritten algorithms that allow the user to perform a +wide variety of raster and vector data analyses. For example, the **Processing Toolbox** contains +tools for identifying features in a vector layer that fulfill certain criteria, extracting selected features from a vector layer and saving them as a new layer, and calculating vector and raster layer statistics. The **Processing Toolbox** can be opened in a new panel to the right of the map view by clicking on the gear icon in the **Attributes Toolbar** or by going to @@ -213,16 +243,7 @@ view by clicking on the gear icon in the **Attributes Toolbar** or by going to For more in-depth information about the Processing Toolbox see the [QGIS User Manual](https://docs.qgis.org/3.28/en/docs/user_manual/processing/toolbox.html) - -## Spatial Querying - -Spatial querying allows the user to select specific layer features based on desired parameters, -or compare features from one layer with features from another layer based on their -spatial relationships or common parameters. Below we describe a specific set of steps for -completing various example query and analysis tasks; however, the QGreenland user will -learn through experience that there is very often more than one way to complete a desired -task in the QGIS platform. We will describe several query and analysis methodologies that -use the QGIS **Processing Toolbox**. +Examples of using the **Processing Toolbox** with QGreenland data are given below. ### Example 1: Selecting from Vector Layers for Specific Features @@ -242,7 +263,7 @@ Which populated regions in Greenland have more than 5000 people? There are a couple of ways to view the selected data points, populated places in Greenland with more than 5000 people. First, you should see the places that meet this parameter -highlighted in the map view (make sure the **Populated Places Layer** is toggled on). You can +highlighted in the **Map View** (make sure the **Populated Places Layer** is toggled on). You can also open the Populated places **Layer Attribute Table** and select **Show Selected Features** in the bottom left corner. This will hide all records in the **Layer Attribute Table** except for the ones you selected, the locations with populations greater than 5000 people. @@ -266,78 +287,85 @@ What is the average size of Greenland’s populated areas? The **Basic statistics for fields** window should automatically switch to a view of the Log where you will see the results for the population basic statistics -(Fig. 8). The value ‘MEAN’ will tell you the average size of Greenland’s +({numref}`vector_layer_stats`). The value ‘MEAN’ will tell you the average size of Greenland’s populated places (702 people). The value ‘SUM’ will tell you the total number of people in Greenland’s metropolitan areas (55,494 people). -![vector_layer_stats](/_images/vector_layer_stats.png) -Fig. 8: Results of Example 2: Vector Layer Statistics + +```{figure} /_images/vector_layer_stats.png +--- +alt: Vector layer stats +name: vector_layer_stats +--- +Results of Example 2: Vector Layer Statistics +``` ### Example 3: Simple Raster Analysis What is a good estimate of the Greenland ice sheet’s volume? -1. In the **Processing Toolbox**, go to **Raster analysis -> Raster surface volume**. This - is an algorithm that calculates the volume under a raster grid’s surface. -2. Fill in the following parameters: - -Input layer = Ice thickness (150 m) - -There will only be one option for Band number - -Base level = should already be set to 0 This is the minimum pixel value in the Ice - thickness layer. - -Method = Count only above base level (since we are interested in ice thickness values - greater than zero) - -Save the Surface volume report, the output for this algorithm, in a temporary file or in a - desired location on your computer. -3. Click **Run** and close the **Raster** surface volume window. -4. You should now see a panel underneath the **Processing Toolbox** called **Results Viewer** (Fig. 9), - which will direct you to the location of the results html file for - this calculation. Open the file. - -The results file should contain three numbers: volume, pixel count, and area. The volume is -the volume of the Greenland ice sheet in units of m3. The results should show that the Green- -land ice sheet has a volume of 2,942,360,633,311,806 m3, or about 2.9 million km3. +See the [Calculate the volume of the Greenland ice +sheet](#calculate-volume-greenland-ice-sheet-tutorial) tutorial for an example +of how to utilize the **Raster Surface Volume** tool. ### Example 4: Using the Raster Calculator How does the maximum sea ice concentration (%) around Greenland and -the surrounding land masses in 2020 compare to the maximum sea ice -concentration a decade earlier (2010)? +the surrounding land masses in 2021 compare to the maximum sea ice +concentration a decade earlier (2011)? The **Raster Calculator** is a tool that allows you to perform calculations on one or more raster layers. For example, if you wanted to convert a raster layer that is in -km2 to mi2, you could use the raster calculator. In this example, we’re going to use -the raster calculator to subtract one layer from another. Note: There is a different +km2 to mi2, you could use the raster calculator. In this example, we are going to use +the raster calculator to subtract one layer from another. + +```{note} +There is a different **Raster Calculator** that can be accessed in the **Menu Bar** by going to **Raster -> Raster Calculator**. This calculator is different from the one in the **Processing Toolbox** used in this example: +``` + 1. In the **Processing Toolbox**, go to **Raster analysis -> Raster calculator**. 2. In the window that appears, you are going to build a mathematical expression using the layers and operators in the **Expression Box**: - a) In the **Layers** box, scroll down and double click on the March2020@1 layer (this - is the layer for the NSIDC’s sea ice concentration data from March 2020). You + a) In the **Layers** box, scroll down and double click on the `March2021@1` layer (this + is the layer for the NSIDC’s sea ice concentration data from March 2021). You should see it show up in the **Expression Box** in quotations (“ “). b) Either type in the minus (-) symbol or click on it under **Operators**. It should show up after the layer you just chose. - c) In the **Layers** box, scroll to and double click on the March2010@1 layer. It should - show up after the minus sign, again in quotations (Fig. 10). + c) In the **Layers** box, scroll to and double click on the `March2011@1` layer. It should + show up after the minus sign, again in quotations ({numref}`raster_calc`). d) For **Reference layer**, it’s recommended you choose either of the two layers used in the expression. Click on the three dots [...] which will open up another window and allow you to choose the reference layer by checking the box next to the layer name. 3. Click **Run** and close the window. -![results_viewer](/_images/results_viewer.png) -Fig. 9: To view the results of the **Raster** surface volume analysis, click on the link + +```{figure} /_images/results_viewer.png +--- +alt: Results Viewer +name: results_viewer +--- +To view the results of the raster surface volume analysis, click on the link next to ‘File path’ in the **Results Viewer Panel** below the **Processing Toolbox**. +``` + -![raster_calc](/_images/raster_calc.png) -Fig. 10: The **Raster Calculator** expression for Example 4. +```{figure} /_images/raster_calc.png +--- +alt: Raster Caclulator +name: raster_calc +--- +The **Raster Calculator** expression for Example 4. +``` The output layer will appear in the **Layers Panel** (likely named **Output**). You can right click on it and rename it if you like. The values next to the colored boxes below the output file (likely black and white boxes) will tell you the minimum and maximum values of the resulting raster layer. In this case, the numbers will be the difference in the maximum sea ice concentration -(%) between 2010 and 2020, where positive values indicate an increase between 2010 and -2020 (endmember = +80%), and negative values indicate a decrease (endmember = -95%). +(%) between 2011 and 2021, where positive values indicate an increase between 2011 and +2021 (endmember = +80%), and negative values indicate a decrease (endmember = -95%).