diff --git a/_images/en_greenland_africa.png b/_images/en_greenland_africa.png new file mode 100644 index 000000000..103fa531c Binary files /dev/null and b/_images/en_greenland_africa.png differ diff --git a/_sources/content/Modul_2/en_qgis_geodata_concept.md b/_sources/content/Modul_2/en_qgis_geodata_concept.md index aea845947..289e512ff 100644 --- a/_sources/content/Modul_2/en_qgis_geodata_concept.md +++ b/_sources/content/Modul_2/en_qgis_geodata_concept.md @@ -240,10 +240,9 @@ Layers in a GIS. Source: [CartONG](https://cartong.pages.gitlab.cartong.org/lear ## Projections ### Introduction -:::{dropdown} Video: Why all world maps are wrong -:open: + -::: + An important issue when creating a map of a region, is that it is impossible to create a representation of a sphere on a 2D plane without distorting the map. The transformation of a 3D object onto a flat surface can be done with the help of a __projection__. Over the centuries, cartographers and mathematicians have developed a multitude of different methods to project the earth onto a flat surface. However, it is never possible to correctly represent the world on a flat surface (see the video above). @@ -270,6 +269,8 @@ figure below). Furthermore, the further away from the equator you get, the more The mercator projection is famous for distorting the size of different countries. You can check the true size in comparison to different placements on the map on [TheTrueSize.com website](https://www.thetruesize.com). A popular example is Greenland in comparison with Africa, which seem on the map to be about the same size, but in reality Africa is a lot bigger. +::: + ```{figure} /fig/en_greenland_africa.png --- diff --git a/content/GIS_AA/en_qgis_historical_impact_assessment_sudan.html b/content/GIS_AA/en_qgis_historical_impact_assessment_sudan.html index 75427abd0..c24568912 100644 --- a/content/GIS_AA/en_qgis_historical_impact_assessment_sudan.html +++ b/content/GIS_AA/en_qgis_historical_impact_assessment_sudan.html @@ -3698,7 +3698,7 @@
Import the previously created CSV file into QGIS. Open the Data Source Manager
and select the Delimited Text
section. Here you can input your CSV-file and depending on the File Format
you need to define Costum delimiters or you can just select CSV. Always check the Sample Data output at the bottom to see if the import is working as expected. You propably will also need to check the Record and Fields Options
and specify if your first record is a header or already data. Lastly, it is important to specify the Geometry Definition
, were you can just select No geometry
. An example will be shown in Fig. 242.
Import the previously created CSV file into QGIS. Open the Data Source Manager
and select the Delimited Text
section. Here you can input your CSV-file and depending on the File Format
you need to define Costum delimiters or you can just select CSV. Always check the Sample Data output at the bottom to see if the import is working as expected. You propably will also need to check the Record and Fields Options
and specify if your first record is a header or already data. Lastly, it is important to specify the Geometry Definition
, were you can just select No geometry
. An example will be shown in Fig. 243.
Note
@@ -3707,23 +3707,23 @@For this example we will use geodata that contains information about the states of Sudan. Make sure that your geodata has the admin_1_PCODE column that will be used for joining the table data with the geodata. We will use the tool Join attributes by field value
. And select the corresponding columns. This is shown in Fig. 243 below.
For this example we will use geodata that contains information about the states of Sudan. Make sure that your geodata has the admin_1_PCODE column that will be used for joining the table data with the geodata. We will use the tool Join attributes by field value
. And select the corresponding columns. This is shown in Fig. 244 below.
The information can now be visualized on a spatial scale and maps can be created to transport important information. An example could be to visualize the total affected population for the year of 2020 on state level. But we can also visualize more specific impact types such as damaged schools or damaged sanitation. This is how such a map could look like.
@@ -3750,7 +3750,7 @@Now we export this excel sheet as a CSV file and import it into QGIS. We will open the Data Source Manager
and select the Delimited Text
section. Here we need to do the following specifications (Fig. 245).
Now we export this excel sheet as a CSV file and import it into QGIS. We will open the Data Source Manager
and select the Delimited Text
section. Here we need to do the following specifications (Fig. 246).
Note
@@ -3759,25 +3759,25 @@The next step follows the same logic as step 2 in the previous example. We will use geodata that contains information about the states of Sudan and join them with the imported CSV data. We will use the Join attributes by field value
tool and select the ADM1_PCODE as the table field used for the join. An example is shown in Fig. 246.
The next step follows the same logic as step 2 in the previous example. We will use geodata that contains information about the states of Sudan and join them with the imported CSV data. We will use the Join attributes by field value
tool and select the ADM1_PCODE as the table field used for the join. An example is shown in Fig. 247.
Now we can visualise our results using Graduated
and selecting the corresponding column of the attribute table Sum flood events
. Select an appropriate color scheme and start creating your map. Your final product could look like Fig. 247.
Now we can visualise our results using Graduated
and selecting the corresponding column of the attribute table Sum flood events
. Select an appropriate color scheme and start creating your map. Your final product could look like Fig. 248.
We can expand this analysis by also including the affected population an calculate the average number of affected population per flood event on state level.
@@ -3791,21 +3791,21 @@Sum affected pop
. Export the subset as a CSV file.
The next steps in QGIS will follow the same logic as before. Import the data and join the table onto your output from the previous task. This will look the following Fig. 239.
The next steps in QGIS will follow the same logic as before. Import the data and join the table onto your output from the previous task. This will look the following Fig. 240.
Now we will calculate the the average number of affected population per flood event on state level. To do so, we need to activate the editing mode for our geodata clicking on this symbol . In the next step we will open the Field calculator
. Here we will calculate the sum of the affected population divided by the number of flood events for each state. Your calculation will look like Fig. 240.
Now we will calculate the the average number of affected population per flood event on state level. To do so, we need to activate the editing mode for our geodata clicking on this symbol . In the next step we will open the Field calculator
. Here we will calculate the sum of the affected population divided by the number of flood events for each state. Your calculation will look like Fig. 241.
Sum flood events
.
Now we export this excel sheet as a CSV file and import it into QGIS. We will open the Data Source Manager
and select the Delimited Text
section. Here we need to do the following specifications (Fig. 245).
Now we export this excel sheet as a CSV file and import it into QGIS. We will open the Data Source Manager
and select the Delimited Text
section. Here we need to do the following specifications (Fig. 246).
Flood events in Sudanese states for all the recorded years
In this section we want to analyse and visualise all recorded flooding events for all the Sudanese state. With our filter for the Impact-Type we derive information for the years 2003 until 2021.
Now we impoer the file “Floods_Sudan_all_years” from the input folder. We will open the Data Source Manager
and select the Delimited Text
section. Here we need to do the following specifications (Fig. 245).
Now we impoer the file “Floods_Sudan_all_years” from the input folder. We will open the Data Source Manager
and select the Delimited Text
section. Here we need to do the following specifications (Fig. 246).
The next step follows the same logic as step 2 in the previous example. We will use geodata that contains information about the states of Sudan and join them with the imported CSV data. We will use the Join attributes by field value
tool and select the ADM1_PCODE as the table field used for the join. An example is shown in Fig. 246.
The next step follows the same logic as step 2 in the previous example. We will use geodata that contains information about the states of Sudan and join them with the imported CSV data. We will use the Join attributes by field value
tool and select the ADM1_PCODE as the table field used for the join. An example is shown in Fig. 247.
Now we can visualise our results using Graduated
and selecting the corresponding column of the attribute table Sum flood events
. Select an appropriate color scheme and start creating your map. Your final product could look like Fig. 247.
Now we can visualise our results using Graduated
and selecting the corresponding column of the attribute table Sum flood events
. Select an appropriate color scheme and start creating your map. Your final product could look like Fig. 248.
The Sketch Map Tool simplifies participatory mapping, by facilitating the creation and digitisation of paper-based maps, the so-called Sketch Maps. This low-tech solution enables the offline collection of local knowledge and perceptions with pen and paper maps. Every SketchMap contains a basemap with OpenStreetMap data or satellite imagery, which provides a scale and orientation to the user. Upon uploading pictures of marked maps, the tool automatically digitizes and georeferences the markings to download and integrate into Geographic Information Systems. The Sketch Map Tool combines widely used, analogue mapping with digital analysis, fosters community involvement and the usability of gained results.
@@ -601,7 +601,7 @@For more information on the EVCA:
diff --git a/content/Modul_2/en_data_sources.html b/content/Modul_2/en_data_sources.html index 999904bef..b752836ea 100644 --- a/content/Modul_2/en_data_sources.html +++ b/content/Modul_2/en_data_sources.html @@ -901,7 +901,7 @@An important issue when creating a map of a region, is that it is impossible to create a representation of a sphere +
An important issue when creating a map of a region, is that it is impossible to create a representation of a sphere on a 2D plane without distorting the map. The transformation of a 3D object onto a flat surface can be done with the help of a projection. Over the centuries, cartographers and mathematicians have developed a multitude of different methods to project the earth onto a flat surface. However, it is never possible to correctly represent the world on a flat surface (see the video above). Every projection distorts either the length between two points, the angles between two lines (directions), or the size of an area. A projection can only correctly represent one of these three dimensions. This means, that depending on the projection method, your world map will not represent the size, angles, or distances correctly.
+In the dropdown below, you can look at the size distortion of mercator yourself.
-```{figure} /fig/en_greenland_africa.png
----
-width: 600px
-align: center
-name: Comparison Greenland - Africa
----
-Comparison Greenland - Africa. Source: [The True Size of](https://www.thetruesize.com/#?borders=1~!MTYwODM1MTk.MzkyNDUyNg*MjY5NjM4Mzg(MTA1MjgyOTE~!CONTIGUOUS_US*MTAwMjQwNzU.MjUwMjM1MTc(MTc1)MQ~!IN*NTI2NDA1MQ.Nzg2MzQyMQ)MA~!CN*OTkyMTY5Nw.NzMxNDcwNQ(MjI1)Mg)
-```
+:::{dropdown} TheTrueSize.com - compare the effects of different projections
+
+%%html
+<iframe src="https://www.thetruesize.com/#?borders=1~!MTUxNjUyNzI.MzM1OTE0MQ*MzI2NDc5MjY(NjgwODA4Mg~!GL*OTQ3NTExNQ.MjkxMDYzMzM)Mw" width="750" height="500"></iframe>
In the dropdown below, you can look at the size distortion of mercator yourself.
-In GIS, we project the earth onto a flat coordinate system (hence the name coordinate reference system or CRS). @@ -883,21 +871,21 @@
Notice how the shape of the circle stays the same. Out of this, we can conclude that the angles stay the same. However, the circles get bigger the further away they are from the equator, and the distance between these circles change the further they they get from the equator. Therefore, we can conclude that the distances and sizes are being distorted with the mercator projection. The strength of the Mercator projection is that it conserves the angles between to lines. We can see this because the circles stay perfectly circular the further they are from the equator.
The WGS 84 is a CRS which consists of an ellipsoid, that resembles the shape of the earth closely. Instead of metrical units of measurements, it uses angular degrees (latitude and longitude). The shape of the Tissot circles is undistorted near the equator, but becomes elongated on the East-West axis the further it gets away from the equator. Unlike the Mercator projection, there is no distortion on the in the North-South direction. As the circles become distorted, we can deduce that the this CRS distorts the angles.
The World Equidistant cylindrical CRS is equidistant (not distorting the length) along any meridian (cricles of longitude; North to South), and along the two standard parallels. The shape, scale and area distort the further they are away from the standard parallels.
@@ -949,7 +937,7 @@As you can see, smaller regions look skewed and distorted in a global CRS diff --git a/content/Modul_3/en_qgis_data_classification.html b/content/Modul_3/en_qgis_data_classification.html index fa4595025..9d07f6814 100644 --- a/content/Modul_3/en_qgis_data_classification.html +++ b/content/Modul_3/en_qgis_data_classification.html @@ -566,7 +566,7 @@
However, if we want to show which districts have a higher population than others on a map, we need to classify the districts.
@@ -688,7 +688,7 @@In the Item Properties panel, if you keep the Auto update
option checked, new layers added to your project will automatically be added to the legend but you cannot control them individually (rename if necessary, reorder ot remove items).
@@ -739,7 +739,7 @@
To add a scale bar, you can use the Add scale bar
-button on the left toolbar. In the Item Properties panel, customize the following functions
If you can’t see the Atlas Tools, you must first activate the Atlas Toolbar under View
> Toolbars
> Atlas Toolbar
.
Thematic maps display the distribution of specific data or statistically processed information, such as population size, disease incidence, flooding risk, etc. The representation of elements on thematic maps is decided according to the rules of graphic semiology.
These two maps use design elements differently. Topographic maps will use symbols and colours out of convention and readability, whereas in designing thematic maps, the symbols and colours you use depend on the context and the information you want to convey.
@@ -629,14 +629,14 @@Visual variables are the graphical means for visually transcribing information. The visual variables are shape, size, hue, value, texture, and orientation. You can adjust these variables to appropriately represent the data at your disposal. They allows for the expression of relationship of difference, order, association, or quantity between each element, helping to display different information.
For each layer in QGIS, there is a styling panel where you can change the symbology, colour and label for the features in that layer. There are two ways to open the layer styling options in QGIS:
@@ -700,21 +700,21 @@When choosing colour gradients, a clear gradient from lighter to darker colours is usually the most appropriate, as the gradation is easily distinguishable and translates well into black and white. In the figure below, examples A and B are not good colour schemes, as it is difficult to make out the gradation and it does not translate well into black and white. You can achieve a clear sequence by grading the saturation of the colour gradient.
Colour gradients can also encompass multiple hues:
The rules, or filters, are based on an expression. You can use the Expression string builder
to the right of the Filter option in the label panel.
In the colour ramp selector, you can adjust each colour step. On the bottom, you can see a plot for the Hue, Saturation, Lightness and Opacity. The last three in particular are useful to understand how your colour ramp will appear. Gradients from light to dark are easier to read: Check if the plot for the Lightness has a more or less linear plot.
@@ -1009,7 +1009,7 @@When working with similar data (e.g. building types or flooding risk), it is useful to have template styles, that can be quickly loaded into your QGIS-project or saved in your Styling Template library.
diff --git a/content/Modul_4/en_qgis_map_examples.html b/content/Modul_4/en_qgis_map_examples.html index d6dd98a86..ffa01f3e1 100644 --- a/content/Modul_4/en_qgis_map_examples.html +++ b/content/Modul_4/en_qgis_map_examples.html @@ -594,7 +594,7 @@The scale bar is essential to a map since it gives the correspondence between a distance measured on the map and the distance in the real world. There are two types of scales:
@@ -718,7 +718,7 @@The most important groups and their respective functionality that are provided with the field calculator are listed below:
@@ -873,7 +873,7 @@Information on road infrastructure for humanitarian aid operations is of great importance and can be easily retrieved from open-source data sources like OpenStreetMap. However, this information is often included in extensive datasets that contain a significant amount of irrelevant details for specific operations or it covers a lot more area than is necessary for the operation. To make working with this data more efficient, it is common practice to clip the data to the area of interest. In addition to clipping, data can often be filtered, as described in the first part of Module 5.
@@ -605,7 +605,7 @@There are several variations in buffering. The buffer distance or buffer size can vary according to the numerical values provided. The numerical values have to be defined in map units according to the Coordinate Reference System (CRS) used with the data.
@@ -730,7 +730,7 @@QGIS provides a range of tools that allow users to delve into spatial relationships and leverage them to enhance their datasets.
@@ -797,7 +797,7 @@To create a heatmap you first need a layer containing data points or ‘samples’. These points are distributed in an area with some areas containing more than others. The density of the points in space determines the intensity of the colour on the heat map.
@@ -830,7 +830,7 @@As you can see, the information communicated through the different maps changes drastically. This is why you need to be transparent on what parameters you have set to create the heatmap.
@@ -859,7 +859,7 @@Interpolating data can be highly useful since an extensive data collection is costly and rarely possible. Data collection for continuous phenomena is usually conducted only at a small number of locations. Interpolation models use these points to calculate a raster surface with estimated values for each raster cell.
@@ -972,7 +972,7 @@Keep in mind that IDW interpolation has a few disadvantages. For example, the quality of the calculated statistical surface decreases, if the distribution of sample points is uneven. Additionally, the highest and lowest values in the interpolated surface only occur at sample points, which is probably not the case in the real world. This often results in peaks or pits around the sample data points (see IDW interpolation example) (adopted from the QGIS documentation).
@@ -986,7 +986,7 @@The problem with TIN statistical surfaces is that the surfaces are not smooth and may seem jagged, since they are based on triangles of varying sizes. Furthermore, triangulation is no suited to extrapolate data beyond the area where sample points have been collected (adopted from the QGIS documentation)
diff --git a/content/Modul_7/en_qgis_automation_theory.html b/content/Modul_7/en_qgis_automation_theory.html index 7b159baf1..75b95b728 100644 --- a/content/Modul_7/en_qgis_automation_theory.html +++ b/content/Modul_7/en_qgis_automation_theory.html @@ -573,18 +573,18 @@Graphical Modeler
also known as the Model Builder allows users to create complex models using a simple and intuitive interface. Most analysis tasks in a GIS are not isolated, but part of a chain of operations resulting in a series of inputs and outputs (e.g. clipping the area of interest, performing a spatial join and applying some table functions). Using the Graphical Modeler, this chain of operations can be combined into a single process, which can then be easily re-run with a different set of inputs. Regardless of how many steps and different algorithms are involved in the analysis, a model is executed as a single algorithm, saving time and effort.
The Graphical Modeler can be accessed from the Processing menu Processing -> Graphical Modeler
as shown in Fig. 129.
The Graphical Modeler can be accessed from the Processing menu Processing -> Graphical Modeler
as shown in Fig. 130.
This will open the following window, which contains everything we need to build a model.
In the Graphical Modeler window we can see several icons and menus. Firstly, we will focus on the left window for the Inputs
and Algorithms
section. Inputs are all the input variables or layers for a model, such as a Vector Layer, Raster Layer, String, Boolean, Expression and many others. The Algorithms are all the tools that are used to process the input variables. In the processing chain, one algorithm/tool will return an output that will be used by another/the following tool until the final output is created.
Select the Inputs
tab from the left window and then select the Vector Layer
by either double-clicking or dragging and dropping it onto the model canvas (Fig. 131). This will open the input Parameter Definition window (Fig. 132). In this window we can customize some vector input parameters such as Description
(the name that the user will see when executing the model), Geometry type
(Point, Line, Polygon) and can also define your input as mandatory for your model by ticking the Mandatory
box. It is also possible to select the Advanced
checkbox to set the input to be within the Advanced section. This is particularly useful when the model has many parameters and some of them are not trivial, but you still want to be able to select them.
Select the Inputs
tab from the left window and then select the Vector Layer
by either double-clicking or dragging and dropping it onto the model canvas (Fig. 132). This will open the input Parameter Definition window (Fig. 133). In this window we can customize some vector input parameters such as Description
(the name that the user will see when executing the model), Geometry type
(Point, Line, Polygon) and can also define your input as mandatory for your model by ticking the Mandatory
box. It is also possible to select the Advanced
checkbox to set the input to be within the Advanced section. This is particularly useful when the model has many parameters and some of them are not trivial, but you still want to be able to select them.
Now select the Algorithms
tab. There are many algorithms which are grouped together. If you know where an algorithm is, you can select it directly, otherwise search for it using the search toolbar. For this example we will search for the Buffer
algorithm as shown in Fig. 133. Add it to the model canvas.
Now select the Algorithms
tab. There are many algorithms which are grouped together. If you know where an algorithm is, you can select it directly, otherwise search for it using the search toolbar. For this example we will search for the Buffer
algorithm as shown in Fig. 134. Add it to the model canvas.
When we double-click on it, the Buffer Algorithm window appears, as shown in the figure below.
diff --git a/content/Modul_8/en_qgis_modul_8_ex1.html b/content/Modul_8/en_qgis_modul_8_ex1.html index 2a0349d38..8e7a937c1 100644 --- a/content/Modul_8/en_qgis_modul_8_ex1.html +++ b/content/Modul_8/en_qgis_modul_8_ex1.html @@ -644,7 +644,7 @@Now we have teached our goal of generating a dataset displaying flood affected population. In the context of real world application in the humanitarian sector or the visualisation of data for people/institutions not familiar with GIS, it can be sensible to aggregate rasterdata on the level of administrative units.
@@ -839,7 +839,7 @@As we now have a rough idea which in which districts large populations where affected by floods we want to explore if precipitation data of 2023 shows similar patterns, as heavy rainfall is a major predisposing factor for the occurence of riverine floods: Are the districts experiencing flooding also experiencing the most rainfall?
@@ -890,7 +890,7 @@Discontinous rasters contain catigorical data, where each pixel represents a discrete classvalue rather than a value on a continuous scale. The information in these types of raster is sometimes also suitable for the storage with vector data. Some examples of classified maps include:
@@ -612,7 +612,7 @@The wanted result can be achieved by firstly selecting both of the relevant rasters as inputs for the raster calculator and then using the expression interface to selct all pixels with a elevation above 1500m ( “( “DEM@1” > 1500)”) and a landcover value of “5” (”( “Landcover@1” = 5 ) “) by connecting both expression with the logical operator “AND”. In the calculated raster all pixels that fulfill the condition will have the value “1”, all other pixels the value “0”.
@@ -703,7 +703,7 @@Do you spot any difference in the isochrone shapes? Try playing around and changing the shape of your avoid area.
@@ -619,7 +619,7 @@How would you describe the difference of both isochrones?
@@ -674,14 +674,14 @@Repeat the same procedure but like before with the option polygons to avoid set to the damaged infrastructure dataset.
As you examine the two isochrone datasets, take a closer look for any discernible patterns. When comparing these isochrones to the damaged infrastructure, pay attention to which segments of the infrastructure appear to have the greatest impact. By identifying and analyzing these areas on the map, you can gain valuable insights into the critical infrastructure segments that are likely to significantly affect healthcare accessibility. These observations will enable you to make informed decisions and prioritize the restoration of infrastructure in the Ahr Valley accordingly.
@@ -699,13 +699,13 @@The grey municipalities inhabitants live outside the range of 15 minutes. May you try it with a higher threshold like 30 minutes an see for changes on municipality level.
diff --git a/content/Modul_9/en_qgis_network_analysis_theory.html b/content/Modul_9/en_qgis_network_analysis_theory.html index b989b797f..c289157c1 100644 --- a/content/Modul_9/en_qgis_network_analysis_theory.html +++ b/content/Modul_9/en_qgis_network_analysis_theory.html @@ -580,7 +580,7 @@For further information: [GIScience/orstools-qgis-plugin]
diff --git a/content/Trainers_corner/en_training_graphical_outline.html b/content/Trainers_corner/en_training_graphical_outline.html index 5a01089aa..d2c3903ab 100644 --- a/content/Trainers_corner/en_training_graphical_outline.html +++ b/content/Trainers_corner/en_training_graphical_outline.html @@ -612,7 +612,7 @@Query:
@@ -626,7 +626,7 @@To solve this, press the control button on your keyboard and right-click open.
@@ -650,7 +650,7 @@You can check this using the Add Geometry Attributes
< Geometry Tools
algorithm. The coordinates are different from the coordinates in the other two attribute tables of the other layers.
Always save your reprojected layers by the Export
and Save as
functions because they are only temporarily saved and will disappear after closing the project.
Similar procedure for raster layers …
@@ -740,7 +740,7 @@See also: Geographic Information Systems @@ -804,7 +804,7 @@
See also: Geographic Information Systems @@ -865,7 +865,7 @@
Mercator does enlarge areas farther from the equator, but at least this distortion is the same horizontally and vertically. And it’s trivial to calculate a scale factor to correct measurements (See also: https://en.wikipedia.org/wiki/Mercator_projection#Scale_factor).
@@ -886,7 +886,7 @@
Solution:
@@ -993,14 +993,14 @@How it might look like on your pc:
The standard folder structure has two principal advantages:
@@ -1033,7 +1033,7 @@Source: GISGeography.com
In the item properties panel, if you keep the ‘Auto update’ option checked, new layers added to your project will automatically be added to the legend but you cannot control them individually (rename if necessary, reorder ot remove items).
@@ -685,7 +685,7 @@
To add a scale bar, you can use the add scale bar button on the left toolbar. In the Item Properties panel, customize the following functions
@@ -700,7 +700,7 @@