GeoJSON: Difference between revisions

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GeoJSON is a file format for geographical data. It is a simple text-based format which can be read by humans, but also by computers. Any Geo Dataset in another format can be converted to the GeoJSON file format.


{{learned|what GeoJSON is|how GeoJSON relates to the Tygron Engine|what data can be read into the Tygron Engine|how to prepare your GeoJSON file|how to upload GeoJSON data into the Engine}}
==How to create a GeoJSON file==
To convert a Geo Dataset to a GeoJSON a GIS (Geographical Information System) can be used. ArcGIS Desktop is one example. An open-source alternative is QGIS.


==What is GeoJSON==
*Go to the documentation for [[How_to_create_a_GeoJSON_file_in_ArcMap|ArcGIS]]
GeoJson is a file format, which is meant to store data about geographical features (GIS data). It is a simple text-based format which can be inspected by humans, but is also readable by most GIS software.
*Go to the documentation for [[How_to_create_a_GeoJSON_in_QGIS|QGIS]]


==How GeoJSON relates to the Tygron Engine==
Also take a look at the [[Data_preparation|data preparation]] page for considerations and tips regarding importing geo data.  
[[Project]]s in the Tygron Engine consist of a number of spatial data layers, such as [[construction]]s, [[zone]]s, and [[land]]. When a project is newly created using the [[wizard]], much of this data is already aggregated from [[data sources|available data]]. However, it may be desirable to load additional data into the project. The Tygron Engine can read GeoJSON files for this purpose.


==When to use GeoJSON files==
====Notes====
The Tygron Engine creates projects using the wizard with a number of default data sources. However, some users or organisations may have data which is preferable or complementary to the data already present in the project. This may be for a number of reasons:
The GeoJSON file must conform to a number of prerequisites before it can be loaded properly. Files which do not conform to these prerequisites may not be loaded properly by the {{software}}. The requirements are:
* The project takes place in a location for which there are no data sources connected by default
* The file must be saved in GeoJSON format
* The default data sources are not accurate or up-to-date enough
* The file must have a CRS (Coordinate Reference System) defined
* The project's intended starting situation is not the same as the real, current situation
* There is some form of data which is not covered by the Tygron Engine by default
In these situations, data in the Tygron Engine can be overwritten or supplemented by the user.
 
==Data in the Engine==
When loading a GeoJSON file, it can take the form of a number of data types. Currently, it is possible to use GeoJSON files to automatically create or update a  number of types of data in the world. Data can be loaded in as:
* [[Construction]]s (Constructions placed based on the shapes defined in the file)
* [[Area]]s (Areas placed based on the shapes defined in the file)
* [[Zoning]] (Zones placed based on the shapes defined in the file)
* Construction values (Constructions are modified based on the attributes in the file)
 
==How to prepare a GIS file==
A GIS file can be converted into a GeoJSON file, so that it can be loaded by the Tygron Engine. Any GeoJSON file must conform to a number of prerequisites before it can be loaded properly. Files which do not conform to these prerequisites may not be loaded properly by the Tygron Engine.
* The file must be saved in GeoJSON format.
* The file must use coordinate system EPSG:3857, Pseudo Mercator.
* The file must use character encoding UTF-8.
* The file must use character encoding UTF-8.
* All desired shapes must be polygons. Not lines or points. Non-polygon shapes are ignored.
* All desired attributes must be numerical, so that they can be loaded as valid [[attribute]] values. Attributes with text values are ignored when attempting to load them as attributes. See for steps, [[Data_preparation#Text_attributes|this page]].  
* All desired attributes must be numerical, so that they can be loaded as valid [[attribute]] values. Non-numeric attributes are ignored when attempting to load them as attributes.
To convert a GIS file so that it meets these requirements, almost any GIS application can be used. ArcGIS Desktop is one example. An open-source alternative is QGIS. Whichever application is selected should allow for inspecting the existing shapes, and transforming them into polygons. This can often be done by, for example, creating a buffer around any shape which is not yet a polygon. They should also allow for inspecting and adding attributes to the shapes. Any attribute information which is to be uploaded should be numerical. If any attribute is not numerical, the values of that attribute must either be changed to be valid numbers, or a new attribute must be created with a numerical value based on the desired attribute. When this is done for all desired shapes and attributes, the file must be saved with the proper format. It must be saved in the coordinate system specified above, as a GeoJSON file with UTF-8 character encoding. This results in a single ".geojson" file, which can be loaded into the Tygron Engine.
 
{{editor steps|title=Convert a GIS file|Open the GIS file in a GIS application, such as QGIS|If necessary, turn non-polygon shapes such as lines or points into polygons|If necessary, make sure all desired attributes are numeric|Save the file in GeoJSON format, using EPSG:3857, Pseudo Mercator, with encoding UTF-8}}


===How to prepare a GIS file using QGIS===


==How to load a GeoJSON file into the engine==
==How to import GeoJSON file==
<!--[[File:GeoJSON_received.jpg|framed|right|After either dragging and dropping the GeoJSON file, or selecting a file with the file-selection window, this window will appear.]]-->
<!--[[File:GeoJSON_received.jpg|framed|right|After either dragging and dropping the GeoJSON file, or selecting a file with the file-selection window, this window will appear.]]-->
The Tygron Engine can be provided with a GeoJSON file, either by dragging-and-dropping the relevant file into the Tygron Engine, or by selecting "Import GeoJSON File" from the relevant [[Ribbon]] dropdown menu in the Tygron Engine. When using the dropdown menu, a file-selection screen will appear, so that the relevant GeoJSON file can be selected. When the file has been selected, or dropped into the Engine, a window will appear so that the desired type of data can be selected.
Use the [[Geo Data Wizard]] for importing the created file. Select in step 1 the first option: ''Import a GeoJSON file'' and follow the steps in the wizard.
 
<br>
===Import options===
{{Template:GeoDataOverview}}
After selecting a data type, a new window will appear, which allows configuring how the data will be interpreted. Some options are present for all data types. A few are only applicable for specific data types.
[[Category:Files]]
 
====File selection====
[[File:GeoJSON_option_select.jpg|framed|right|How many shapes intersect with the 3D world, and the "File selection" option.]]
A GIS file can contain a number of features, but when importing them into the Tygron Engine, only the features which lie within the 3D world. When importing a file, at least one feature of the GIS file should be present in the 3D world, or it is not possible to load data from that file. <br style="clear:both">
====Merge polygons====
[[File:GeoJSON_option_merge.jpg|framed|right|The "Merge" option.]]
It is possible to merge all features into a single polygon. This can be useful when the there just needs to be a test for the presence of the data itself, and any subdivision in that data is not relevant for the project. Be carefull when using this options, as it may lead to very large polygons, which may result in a decrease in performance. <br style="clear:both">
====Filter polygons====
[[File:GeoJSON_option_filter.jpg|framed|right|The "Filter" option.]]
When desired, it is possible to filter which features to import into the project. When the filter option is selected, some additional fields become available, which allow for the selection of an attribute and a value to filter on. Only features, the indicated attribute of which has the value entered, will be included in the import. There will be a display of how many features are selected based on the currently selected attribute and value. To help input a valid value, there is also an option to display all valid values for that attribute.<br style="clear:both">
 
====Name====
[[File:GeoJSON_option_name.jpg|framed|right|The "Name" option.]]
Some components in the project can be named, such as [[construction]]s and [[area]]s. For these components, it is possible to select an attribute which will dictate the names of the imported features. If no specific attribute is selected to base a name on, the components are named after the file currently being imported. <br style="clear:both">

Latest revision as of 09:43, 30 January 2023

GeoJSON is a file format for geographical data. It is a simple text-based format which can be read by humans, but also by computers. Any Geo Dataset in another format can be converted to the GeoJSON file format.

How to create a GeoJSON file

To convert a Geo Dataset to a GeoJSON a GIS (Geographical Information System) can be used. ArcGIS Desktop is one example. An open-source alternative is QGIS.

  • Go to the documentation for ArcGIS
  • Go to the documentation for QGIS

Also take a look at the data preparation page for considerations and tips regarding importing geo data.

Notes

The GeoJSON file must conform to a number of prerequisites before it can be loaded properly. Files which do not conform to these prerequisites may not be loaded properly by the Tygron Platform. The requirements are:

  • The file must be saved in GeoJSON format
  • The file must have a CRS (Coordinate Reference System) defined
  • The file must use character encoding UTF-8.
  • All desired attributes must be numerical, so that they can be loaded as valid attribute values. Attributes with text values are ignored when attempting to load them as attributes. See for steps, this page.


How to import GeoJSON file

Use the Geo Data Wizard for importing the created file. Select in step 1 the first option: Import a GeoJSON file and follow the steps in the wizard.

Geo Data
Project Sources
Open data sources • GeoShare • Custom Geometry
Web
WFS • WMS • WCS • CSW • Map service
File
CityGML • DXF • GeoJSON • GeoTIFF • SLPK
Import
Vector • Raster • 2D spatial plan • 3D model (I3S, CityGML)
Export
Vector • Raster • GeoShare Viewer
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