GIS: Geojson is not displayed

[afalenski]

As a user who has uploaded *.geojson files I would like to see this shapefile. I uploaded a file containing all German municipalities (see http://opendatalab.de/projects/geojson-utilities/) as well as my own geojson drawn at https://geojson.io (see attachment). Neither of these geojson files were displayed.

Polygon-DE-0-rough.txt (rename .txt to .geojson; geojson is not allowed in ZenHub)

Include a warning -> if no projection type is given, the warning should be "Projection type of geojson file not specified. Mercator projection is assumed. Map might be distorted if data do not fit Mercator projection." -> if wrong projection type, the warning should be "Incorrect projection type. Incorrect geojson files are not supported."

Think of Tests

• [ ] Excel testsheet needed
• [ ] E2e test needed
• [ ] Integration test needed
• [ ] Unit test needed

Additional context

• [ ] Mockup needed

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[ruegenbfr]

A solution has to deal with 2 aspects:

1. The geojson is using some projection. Can the projection type be used?
2. Provided the geojson contains an appropriate projection. Can the shapes be seen by user?

To 1.: We are using the openlayer library to visualize maps and shape files. This lib has an build in support for the the projection types 'EPSG:4326' and 'EPSG:3857' and some aliases of them. The lib provides a method to detect whether the projection is built in supported. Ergo, question 1 is easy to answer, if we want to use the built in support only.

To 2.: Event with an appropriate projection type, the user might see no shapes, either because (Case A) the dimension of the shapes is zero (only point of interests), or (Case B) the shapes are to small in comparison to the zoom scale or station distances, or (Case C) the shapes are out of focus (e.g. only german stations but a shape file from spain). Case A ist easy to detect, but Case B and C depend on some defintions, in particular 'When exactly are the shapes out of focus?' and 'When are the shapes to small?'

[afalenski]

1) We should definitely use both EPSG which are WGS 84 Web Mercator / WGS 84/Pseudo-Mercator. This "...is a variant of the Mercator map projection and is the de facto standard for Web mapping applications." (https://en.wikipedia.org/wiki/Web_Mercator_projection). 2) The user needs to use one of these two projections. An imported shape must be visible, even if it is just a point of interest. Using the zoom all button in FCL Web the shapes should also be focused. This means if there are 4 stations in Germany and one shape in the USA, the zoom all button should focus the map so that stations AND shape are visible.

[afalenski]

@ruegenbfr Please provide your geojson test file for testing when the 'EPSG:4326' and 'EPSG:3857' projection types have been implemented.

[ruegenbfr]

Warnings are different to the issue description:

• If the user tries to load a geojson without a specified projection type, no warning is presented to the user, because this is in agreement with the current geojson format specification. Which says that the projection type should not be specified and EPSG:4326 is to be used. --> Shape will be shown
• If the user tries to load a geojson with a specified projection type, and the used library supports this projection, no warning is presented to the user --> Shape will be shown
• If the user tries to load a geojson with a specified projection type, which is not supported by the used lib, the warning Data cannot be loaded. Unsupported projection type. Please use geojson with pojection type 'EPSG:4326' or 'EPSG:3857' instead. is shown to the user.

Please test with: Polygon_DE_EPSG3043.geojson Polygon_DE_EPSG4326.geojson Polygon_DE_EPSG3857.geojson Polygon_DE_wo_projection_type_spec.geojson

[afalenski]

• Warning is visible with test file Polygon_DE_EPSG3043.geojson.
• The other geojson test files all show the border of Germany (very crude).
• Looks great with CNTR_BN_01M_2020_3857.geojson from https://ec.europa.eu/eurostat/de/web/gisco/geodata/reference-data/administrative-units-statistical-units/countries (takes about 5s to load)
• Using NUTS_RG_01M_2021_3857.geojson from https://ec.europa.eu/eurostat/de/web/gisco/geodata/reference-data/administrative-units-statistical-units/nuts with all the NUTS3 regions a new feature requests becomes obvious: The opacity of the shapes should be adjustable (see #621). Done.

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  Tested with Machine: SINA

OS: Windows 10

Datasets:

• Example Dataset Polygon_DE_EPSG3043.geojson Polygon_DE_EPSG4326.geojson Polygon_DE_EPSG3857.geojson Polygon_DE_wo_projection_type_spec.geojson

Browsers:

• Google Chrome Version 94.0.4606.81 (Offizieller Build) (64-Bit)
• Firefox Quantum 78.15.0esr (64-Bit)