Coordinate Transformation API

RESTful Coordinate Transformation API offering NSGI defined and NSGI recommended transformations for the Netherlands. Build on top of pyproj and FastAPI.

Assumptions

• API metadata, documentation and source code is in English
• Easily accessible, but correct
• Conforms (as much is possible) to the OGC API Common and the NL API Design rules

pyproj

⚠️ pyproj makes use of it's own proj binaries and PROJ_DIR. These are set when pyproj is build.

Pyproj with default configuration is not capable in performing the right transformations, because our primary transformations layer on the following transformation grids:

Recommended RDNAPTRANS(TM)2018 variant:

• https://cdn.proj.org/nl_nsgi_nlgeo2018.tif
• https://cdn.proj.org/nl_nsgi_rdcorr2018.tif

And the geoid for BESTRANS2020

These transformation grids need to be downloaded from the PROJ.org Datumgrid CDN and put in the correct directory. This can be done in a couple of ways.

1. Enable PROJ_NETWORK environment variable
2. Edit proj.ini file by setting network = on

These will download the necessary files to a cache so they can be use for the correct transformation. But this requires a network connection, preferable we don't want to rely on this network connection and provide these files with the application. This can be done by

1. Mirror https://dcn.proj.org and write the these file to the data directory
2. Download the specific files to the root of the data directory

Development

To install from source requires minimum version of pip: 23.2.1.

Install dev dependencies with:

pip install ".[dev]"

Install enable pre-commit hook with:

git config --local core.hooksPath .githooks

To run debug session in VS Code install the package with pip with the --editable flag:

pip install --editable .

Also install Mypy as follows

mypy --install-types

Check test coverage (install coverage with pip install coverage):

python3 -m coverage run --source=src/coordinate_transformation_api -m pytest -v tests && python3 -m coverage report -m

Validate OAS document:

# install spectral with: npm install -g @stoplight/spectral-cli - then validate openapi doc with:
echo 'extends: "spectral:oas"\n'> ruleset.yaml &&  spectral lint http://127.0.0.1:8000/openapi.json --ruleset ruleset.yaml && rm ruleset.yaml

Install NSGI proj.db

Execute the following shell one-liner to install the NSGI proj.time.dependent.transformations.db as proj.db from the GeodetischeInfrastructuur/transformations repo:

proj_data_dir=$(python3 -c 'import pyproj;print(pyproj.datadir.get_data_dir());')
curl -sL -o "${proj_data_dir}/nl_nsgi_nlgeo2018.tif" https://cdn.proj.org/nl_nsgi_nlgeo2018.tif && \
    curl -sL -o "${proj_data_dir}/nl_nsgi_rdcorr2018.tif" https://cdn.proj.org/nl_nsgi_rdcorr2018.tif && \
    curl -sL -o "${proj_data_dir}/nl_nsgi_rdtrans2018.tif" https://cdn.proj.org/nl_nsgi_rdtrans2018.tif && \
curl -sL -H "Accept: application/octet-stream" $(curl -s "https://api.github.com/repos/GeodetischeInfrastructuur/transformations/releases/latest" | jq -r '.assets[] | select(.name=="proj.time.dependent.transformations.db").url') -o "${proj_data_dir}/proj.db"

⚠️ For 'default' usage, like QGIS, use the proj.db. The coordinate transformation API it self uses the proj.time.dependent.transformations.db for specific time dependent transformations.

Install

pip install .

Run

ct-api

Docker

Build container

docker build -t nsgi/coordinate-transformation-api .

Run container

docker run --rm -d -p 8000:8000 --name ct-api nsgi/coordinate-transformation-api

CityJSON

Generate CityJSON models

wget --no-parent  --recursive https://3d.bk.tudelft.nl/schemas/cityjson/1.1.3/
pip install datamodel-code-generator
datamodel-codegen  --input  3d.bk.tudelft.nl/schemas/cityjson/1.1.3/metadata.schema.json  --input-file-type jsonschema --output cityjson.py

Working with CityJSON (with cjio cli)

Download test/sample data from www.cityjson.org/datasets/.

Creating a subset of CityJSON file (for - for example - testing purposes):

cjio DenHaag_01.city.json subset --random 10 save test_10.city.json

CRS transformation with cjio:

cjio test_1.city.json crs_reproject 4937 save test_1_4937.city.json

flowchart
    input([/transform endpoint]) ==> filetype{content-type<br>request body}
    filetype==> | GeoJSON | dc_param{density-check parameter}
    filetype==> | CityJSON | a4[add response header:<br>density-check-result: not-implemented]
    a4 --> tf
    dc_param ==> |"`default: *true*`"|ms_param{max_segment param}
    ms_param -.-> |max_segment_deviation param| bc[check if data within bbox]
    bc --> |success| dc
    bc --> |failure| output_error_bbox([HTTP 400 with bbox error])

    ms_param ==> |"`max_segment_length param (default: *200*)`"| dc[density check]
    dc_param -.-> |"`*false*`"| a5[add response header:<br>density-check-result: not-run]

    a5 --> tf[transform]

    dc --> |"not applicable: geometrytype is point" | a2[add response header:<br>density-check-result: not-applicable-geom-type]
    dc --> |"success"| a3[add response header:<br>density-check-result: success]
    dc --> |"failure"| a6[add response header:<br>density-check-result: failed]
    a6 --> output_error([HTTP 400 with density check report])
    a2 --> tf
    a3 --> tf
    tf --> output([http 200 response])
    class output_error error
    class output_error_bbox error
    classDef error stroke: red,stroke-width:2px
    style output stroke: green,stroke-width:2px

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