What is GIS? (Theory)#
+General information:#
+-
+
Geoinformatics in general focus on the visualisation, organisation and processing of spatial data.
+Spatial analyses furthermore allow to reveal circumstances and connections between spatial data features:
+-
+
by making use of their spatial location, information layers (or features within a layer) can be analyzed in regard to each other to obtain new information.
+
+
Why are spatial analyses important?#
+Note
+Discuss in groups:
+-
+
Situations in which you benefitted from spatial analyses.
+Situations in which you could may be have benefitted from spatial analyses.
+Main areas where you see potential for spatial analyses in your work.
+
Introduction to GIS:#
+An informal definition#
+-
+
Geographic Information System (GIS) uses maps to show complex information clearly and efficiently.
+For example, in an emergency context, GIS can be used to visualize on a map what is happening, where, how many people are affected, and what their main needs are.
+It can help to summarize information from many different sources.
+This helps peoples to quickly understand the situation and make better informed decisions.
+
A formal definition#
+-
+
A Geographic Information System (GIS) is a digital system that connects data to maps.
+It allows us to collect, manage, analyse, and visualise data assigning them a position on Earth’s surface.
+GIS reveals deeper insights into data, clearly demonstrating patterns and helping us to understand geographic context.
+Benefits include more insightful analysis, improved communication, and ultimately better evidence-based decision-making.
+It’s rooted in geography, the field of science devoted to the study of the lands, features, inhabitants, and phenomena of the Earth.
+GIS software can display multiple types of data on a map.
+
GIS components#
+-
+
Hardware
+Software
+Data
+People
+Workflows
+
We use GIS for:#
+-
+
Creating interactive queries (Querying)
+Analysing spatial information (Spatial analysis)
+Editing and visualizing data in maps (Editing)
+Present the results of all these operations (Map making)
+
GIS in humanitarian responses#
+GIS has many applications in the humanitarian field:
+-
+
Refugee/IDP camp planning
+Mapping remote areas to facilitate access
+Keep track of field operations
+Support security decisions
+Support operations planning
+Identify areas most affected by disasters
+
Tip
+A few examples:
+-
+
REACH Initiativehttps
+- +
- +
- +
- +
Paper maps and cartography#
+What is spatial analysis?#
+-
+
Spatial analysis studies entities and events using their topological, geometric, or geographic properties.
+It includes a variety of techniques to analyse geographic data.
+Data can be added to a map as layers and they can interact with each other.
+GIS enables you to work with these layers to explore critically important questions and find answers to those questions.
+
An example from the past: John Snow’s Cholera map#
+In 1854 an outbreak of cholera occurred in London, England. The most common theory was that the disease was spread through the air. Dr.John Snow believed that the danger was in the water. He made a map to analyse the number of deaths in Soho per house block. He added the location of water pumps on the map. +He found a correlation between one specific water pump and the number of infections.
+Tip
+Example:
+GIS vs Cartography#
+-
+
Cartography is the study and practice of making maps.
+A GIS is a modern extension of traditional cartography.
+Both contain examples of a base map to which additional data can be added.
+The differences are that there is no limit to the amount of additional data that can be added to a GIS map.
+Cartographic maps are often extremely simplified as there are limits to the amount of data that can be physically and meaningfully stored on a small map.
+GIS uses analysis and statistics to present data in support of particular arguments which a cartographic map cannot do.
+You can use GIS for cartography.
+
GIS vs Cartography
+General reference maps#
+-
+
Show important physical features of an area
+Include natural and man-made features
+Usually meant to help for navigation or discovery of locations
+Usually fairly simple
+Can be stylized based on the intended audience
+
Reference map of Iraq
+Infrastructure maps#
+-
+
Display relevant features and structures in a specific area
+Help planning and navigation
+High level of detail
+Produced after field data collection
+
+Infrastructure map of Nigeria
+Thematic maps#
+-
+
Focus on a specific theme or subject
+Features on the map represent the subject being mapped
+Use colours and shapes to display quantitative and qualitative data
+Rise awareness about a specific subject
+
Thematic map of Africa
+Analysis maps#
+-
+
Analyse data in respect to their geographic location
+Create new layers of information from the interaction between multiple features
+Use colours and shapes to help users understand specific events
+Support decision makers
+Generally display a greater level of detail
+
Analysis map of Yemen
+Situation/Descriptive maps#
+-
+
Used to better visualize a specific ongoing and/or past situation
+Maps can include narrative and graphic elements
+Can be used in reports and/or to raise awareness on a specific event
+
Situation map from Tilkaif to Mosul
+Mapping and GIS#
+-
+
Mapping focuses on representing spatial phenomena statically (paper formats) or dynamically (web formats) It is a major component of GIS.
+Geographic Information Systems refer to a set of systems related to the processing of geographic information (spatial data) GIS have their own unique software capable of storing, processing, representing and analysing geographical data.
+
Structure GIS System
+Data behind the Map
+Mapping and GIS-Spreadsheet
+Graphic information
+For further information have a look here:
+PDF documentation Mapping and GIS, p. 6 - 10
+Examples for GIS created maps#
+The battle against Malaria - Burundi -- Coordination in camps - Bangladesh
+
Malaria#
+-
+
A fatal, mosquito-borne (vector) disease, killing over 620,000 people in 2020 (WHO).
+
The battle against Malaria#
+2 methods for the control of vector-borne diseases
+-
+
Use of insecticide-treated nets
+Insecticides for indoor residual spraying
+
Indoor Residual Spraying (IRS)#
+This involves spraying the inside of houses, usually once or twice a year. However, in order to obtain significant community protection, a high level of coverage is required. IRS provides community protection when at least 85% of homes in a targeted area are sprayed.
+Gis for coordination in the camps#
+-
+
The mega refugee camp in Bangladesh in 2018
+Navigational aid: +to help field teams move around in such a huge camp without getting lost
+Planning support: +Population estimate, distribution of tents and infrastructure, risk assessment, …
+
For further information have a look here:
+PDF documentation Examples for GIS created maps, p. 45 - 53
+Tip
+Some more examples:
+The examples presented below illustrate some more map productions by indentiying the need, software, key steps and deliverables associated with them. They are not exhaustive but allow to have a vision of the different possibilities of cartographic rendering through different requests and various tools discussed in the toolbox.
+-
+
Static products: https://cartong.pages.gitlab.cartong.org/learning-corner/en/2_mobilize_mapping_gis/2_1_static_mapping
+Dynamic products: https://cartong.pages.gitlab.cartong.org/learning-corner/en/2_mobilize_mapping_gis/2_2_dynamic_mapping
+A field example: https://cartong.pages.gitlab.cartong.org/learning-corner/en/2_mobilize_mapping_gis/2_3_field
+
For further information have a look here:
+PDF documentation Mobilizing mapping and GIS
+Web GIS platforms#
+GIS Applications#
+-
+
You can use GIS through multiple applications, from desktop software, to online platforms, to mobile apps.
+At a basic level, you can perform limited geospatial tasks with apps such as Google Earth or Google Maps.
+As a GIS professional, you will mostly use a desktop software, which could be either: Proprietary or Open source.
+Open Street Maps (OSM): +https://www.openstreetmap.org/#map=14/49.4192/8.7235 +An open geographic database updated and maintained by a community of volunteers via open collaboration. It works using a tag system (each feature is categorized through tags).
+uMap: https://umap.openstreetmap.fr/en/ +Online tool to create maps using OSM layers.
+Felt: https://felt.com/ +An easy tool to create maps. You can draw, create feature and upload shapefiles.
+Wikimapia: https://wikimapia.org/#lang=de&lat=49.402500&lon=8.633100&z=12&m=w +Online editable map service. Updated and maintained by contributors all over the world. It uses local knowledge, making it particularly useful in remote areas.
+Google Maps: https://www.google.com/maps/d/ +Limited, but it allows to upload layers, create and export features, share simple maps.
+
Geo mobile apps#
+-
+
Qfield: https://docs.qfield.org/ +Through QFieldCloud, you can open your QGIS projects on Qfield on your mobile device. Any edit made on the map in the app can then be synced and displayed in QGIS.
+OsmAnd: https://osmand.net/. +Using OSM basemap, it’s a good app for offline navigation. You can upload kml-files to display on the map, as well as recording your trips and then export them to kml.
+GeoODK: http://geoodk.com/index.html +Combines ODK with a geo app. You can collect data through ODK surveys and display them on a map, in addition to easily create polygons and add information to them.
+
See also:
+ +PDF documentation Webmapping tools
+Geo Mobile Apps overview (general understanding)#
+Why are spatial analyses so important?#
+Tip
+Discuss in groups:
+-
+
Situations in which you benefitted from spatial analyses
+Situations in which you could maybe have benefitted from spatial analyses
+Main areas where you see potential for spatial analyses in your work
+
Spatial analyses in QGIS#
+Manual selection of features in QGIS#
+-
+
Click on the respective features directly in the map: Selection when highlighted in the map and in the attribute table
+Select feature by polygon: Choose „Select feature by polygon“ tool and draw a polygon around the feature of interest
+
Save selection (same for all selection types)#
+-
+
Save selected features as new layer/ file:
+-
+
Right click on layer, choose „Export“ and „Save selected features as… “
+Choose location where the data should be saved in,
+Make sure that the mark at „Save only selected features“ is set
+
+
Select by Location Tool#
+-
+
Select all features that meet one or more criteria with regard to a spatial reference
+
-
+
All features that meet one or more criteria with regard to a spatial reference
+-
+
Example: Select all features in the Dakar and Thies region.
+
+
Step by step:
+-
+
Select features from input layer (in example select “healthsites”)
+Check all geometric predicates that are relevant
+Select second input layer (in example “Dakar_Thies”)
+Create new selection
+
Combination of spatial queries by choosing in dropdown menu („Modify current selection by“, if multiple selections are conducted in a row)
+-
+
Adding to current selection (OR)
+-
+
Example: To identify and select all features that meet only one of the selected criteria
+
+Selecting within current selection (AND)
+-
+
Example: To identify and select all features that meet all of the selected criteria
+
+Remove from current selection (AND NOT)
+-
+
Example: To identify and select all features that meet one of the selected criteria but not the other
+
+
Non-Spatial Analyses in QGIS#
+Manual selection:#
+-
+
Clicking on the respective features directly in the attribute table:
+
Select feature by expression:#
+-
+
Open the attribute table and open the „Select features using an expression“ window:
+
-
+
Different kinds of operators to choose from: +Arithmetic operators: >, < , =, !=
+-
+
Example: Select all health facilities in Senegal which have more than one nurse as staff.
+
+
Step by step:
+-
+
Under “Fields and Values”: Select column name “staff_nurs”
+Under “Operators”: Select ”>“
+Under “Fields and Values”: Click again on selected column name to see all unique values (right bottom, click on “All Unique”)
+Select the respective unique value (here: ‘1’)
+Click on “Select features”
+
-
+
Different kinds of operators to choose from: +String operators:
+-
+
For example “LIKE“: Select all health facilities that are doctors
+
+
Step by step:
+-
+
Under “Fields and Values”: Select column name “amenity”
+Unser “Operators”: Select ”LIKE“
+Under “Fields and Values”: Click again on selected column name to see all unique values (right bottom, click on “All Unique”)
+Select the respective unique value (here: ‘doctors’)
+Click on “Select features”
+
-
+
Different kinds of operators to choose from: +Logical operators: “AND“ and “OR“ → Enable to combine different queries/criteria
+
Table Functions#
+Similar to what you can do in a spreadsheet.
+-
+
Create Field: add a new attribute and manually insert values
+Delete Field: remove attributes that are redundant or attributes you will not work with
+Calculate Field: e.g. calculate new attribute population density
+
Table Functions - Delete Fields#
+Step by step:
+-
+
Start edit mode
+Click on delete fields button
+Save and stop edit mode
+
Table Functions - Field Calculator#
+-
+
Calculate area in square meters first and then divide by 1,000,000 to get square kilometers
+Calculate population density as people per square kilometer
+
Geoprocessing Tools (Selection) in QGIS
+Geoprocessing Tools - Overview#
+ + +Tip
+Example for a clip:
+Creates a selection based on the spatial relationship between each feature in the input layer and the features in an additional layer.
+Step by step:
+-
+
Input Layer: Layer from which the selection is clipped
+Overlay Layer: Area of interest that the input layer will be clipped to
+
Tip
+Example for a buffer:
+-
+
Computes (a) buffer area(s) for all the features in an input layer, using a specified distance
+
Step by step:
+-
+
Input Layer: Layer around which features the buffer(s) are to be created
+Distance: Choose a value and unit (make sure that your input data is projected)
+Segments: Add value
+Mark „Dissolve result“ to automatically dissolve the buffer outputs
+If individual buffers are needed, leave blank
+
Tip
+Examples for buffer usage:
+Philippines: Taal Volcano, Base surge hazard map +https://www.phivolcs.dost.gov.ph/vault/1BaseSurge_Layout-Jan2020_A0_v5.jpg
+ +Nepal: Earthquake, april 2015 +https://reliefweb.int/sites/reliefweb.int/files/resources/reach_npl_map_earthquakeaffected_27apr2015_a3.pdf
+ +Fukushima: may 2011, Integrated doce results +https://www.emsics.com/five-years-fukushima-incident-management-considerations/
+ +Buffer: with and without “dissolve”#
+With dissolve results:
+ +Without dissolve results:
+ +Non-Spatial Joins in QGIS#
+-
+
Choose “Join Attributes by Field Value” Tool (use search tool):
+Adds attributes of a non-spatial table to the layer
+Enables join using a field/column that is present in both data sets
+
Step by step:
+-
+
Input layer: Vector layer
+Table field: Field/ column that exists in both data sets (name of column in vector layer)
+Input layer 2: Text/csv/xls data
+Table field 2: Field/ column that exists in both data sets (name of column in text/csv/xls)
+Join type: Select „Take attributes of the first matching feature only (one-to-one)“.
+Define output layer name and destination or leave at temporary layer
+
Tip
+Hint
+If a table join does not work via the “Join Attributes by Field Value” tool, a join can also be performed via the layer properties (right-click, Properties) under the Join tab.
+Spatial Joins in QGIS#
+Choose “Join Attributes by Location” Tool:
+-
+
Adds additional attributes of the join layer to the input layer based on the spatial relationship
+Input Layer: Dataset you want to enrich
+Join layer: Dataset with additional information/attributes +(you can specify which fields of the join layer should be added)
+
A galaxy of tools#
+GIS comes with a galaxy of tools that are constantly evolving. An increasing number of traditional tools are now capable of supporting geographic information (Excel, Power BI, Adobe Illustrator…)
+An overview:#
+-
+
Mobile data collection tools
+
The latter make it possible to collect data via mobile or tablet, and often to visualize and exchange it with other platforms according to a common format.
+-
+
Mapping tools
+
These tools provide a simple vizualisation of geographic data, and allow for the production of maps.
+-
+
GIS tools
+
As opposed to the previous ones, these more advanced tools are very comprehensive and allow for advanced analyses to be carried out on the geographical components of data.
+-
+
Webmapping tools
+
These tools make it possible to manipulate and create maps online in a very simple way directly in a web browser.
+For further detalied information have a look here:
+PDF documentation GIS-related tools, p. 36 -41
+