Web APIs

for Geospatial Applications



Jakob Miksch
2021-11-22
part of lecture "Selected Topics"
Z_GIS, University of Salzburg

Jakob Miksch

jakob@meggsimum.de
@jakobmiksch
@jakobmiksch

• Geospatial Developer
• OSGeo Foundation Charter Member

meggsimum

info@meggsimum.de
@meggsimum
@meggsimum

• meggsimum.de
• services in the field of GIS, webmapping & SDI
• tailored WebGIS solutions
• software development
• geodata
• consulting and training

## (Web) Application Programming Interface - ubiquitos in the web - for data exchange - software development

## Web API: OpenWeatherMap  <small> <a href="https://openweathermap.org/api">https://openweathermap.org/api</a> </small>

## Web API: Google Street View  <small> <a href="https://developers.google.com/maps/documentation/streetview/overview">https://developers.google.com/maps/documentation/streetview/overview</a> </small>

## Web API: NASA  <small> <a href="https://api.nasa.gov/index.html">https://api.nasa.gov/index.html</a> </small>

## Web API: Pokemon  <small> <a href="https://pokeapi.co/">https://pokeapi.co/</a> </small>

## API 

## Exchange formats - XML - JSON

## XML ```xml <breakfast_menu> <food> <name>Belgian Waffles</name> <price>$5.95</price> <description> Two of our famous Belgian Waffles with plenty of real maple syrup </description> <calories>650</calories> </food> <food> <name>Strawberry Belgian Waffles</name> <price>$7.95</price> <description> Light Belgian waffles covered with strawberries and whipped cream </description> <calories>900</calories> </food> <food> <name>Berry-Berry Belgian Waffles</name> <price>$8.95</price> <description> Light Belgian waffles covered with an assortment of fresh berries and whipped cream </description> <calories>900</calories> </food> <food> <name>French Toast</name> <price>$4.50</price> <description> Thick slices made from our homemade sourdough bread </description> <calories>600</calories> </food> <food> <name>Homestyle Breakfast</name> <price>$6.95</price> <description> Two eggs, bacon or sausage, toast, and our ever-popular hash browns </description> <calories>950</calories> </food> </breakfast_menu> ``` <small> <a href="https://www.w3schools.com/xml/simple.xml">https://www.w3schools.com/xml/simple.xml</a> </small>

## JSON ```json { "squadName": "Super hero squad", "homeTown": "Metro City", "formed": 2016, "secretBase": "Super tower", "active": true, "members": [ { "name": "Molecule Man", "age": 29, "secretIdentity": "Dan Jukes", "powers": [ "Radiation resistance", "Turning tiny", "Radiation blast" ] }, { "name": "Madame Uppercut", "age": 39, "secretIdentity": "Jane Wilson", "powers": [ "Million tonne punch", "Damage resistance", "Superhuman reflexes" ] }, { "name": "Eternal Flame", "age": 1000000, "secretIdentity": "Unknown", "powers": [ "Immortality", "Heat Immunity", "Inferno", "Teleportation", "Interdimensional travel" ] } ] } ``` <small> <a href="https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Objects/JSON">https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Objects/JSON</a> </small>

## GeoJSON ```json { "type": "Feature", "geometry": { "type": "Point", "coordinates": [125.6, 10.1] }, "properties": { "name": "Dinagat Islands" } } ``` <small> <a href="https://geojson.org/">https://geojson.org/</a> </small>

## HTTP Requests `GET` <br> `POST` <br> `PUT` <br> `PATCH` <br> `DELETE` <br> ... <small> <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods">https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods</a> </small>

## URL - Query Parameter ``` https://www.example.com? color=blue& type=dark ```

## URL - Query Parameter - WMS example ``` https://services.meggsimum.de/geoserver/mgsm-world/wms? service=WMS& version=1.1.0& request=GetMap& layers=mgsm-world:ne_10m_admin_0_countries& bbox=-180.0,-90.0,180.0,83.6341& width=768& height=370& srs=EPSG:4326& format=image/png ``` <img src="img/wms-world-map.png" class="plain" height="200"/>

## API Types - SOAP - REST ([example](https://pokeapi.co/)) - GraphQL ([example](https://beta.pokeapi.co/graphql/console/)) - ...

## OGC Standards - `WMS`, `WFS`, `WCS`, ... - example: [GeoServer (meggsimum)](https://services.meggsimum.de/geoserver/web/) - RESTful [OGC API](https://ogcapi.ogc.org/) as successor

## Authentication typically via Tokens ```url https://api.openrouteservice.org/v2/directions/driving-car? api_key=<--ADD_YOUR_API_KEY-->& start=8.681495,49.41461& end=8.687872,49.420318 ```

## Tools - webbrowser - commandline - programming language - desktop tools

## Web Browser with developer tools or JavaScript 

## Commandline ```bash curl -X GET \ 'https://photon.komoot.io/api/?q=salzburg&limit=2' ``` returns: <!-- .element: class="fragment" data-fragment-index="1" --> ```json { "features": [ { "geometry": { "coordinates": [ 13.0464806, 47.7981346 ], "type": "Point" }, "type": "Feature", "properties": { "osm_id": 86538, "osm_type": "R", "extent": [ 12.9856478, 47.8543925, 13.1272842, 47.7512115 ], "country": "Austria", "osm_key": "place", "countrycode": "AT", "osm_value": "city", "postcode": "5020", "name": "Salzburg", "state": "Salzburg", "type": "city" } }, { "geometry": { "coordinates": [ 13.25, 47.4166667 ], "type": "Point" }, "type": "Feature", "properties": { "osm_id": 86539, "osm_type": "R", "extent": [ 12.0760956, 48.0414691, 13.996125, 46.943858 ], "country": "Austria", "osm_key": "place", "countrycode": "AT", "osm_value": "state", "name": "Salzburg", "type": "state" } } ], "type": "FeatureCollection" } ``` <!-- .element: class="fragment" data-fragment-index="1" -->

## Python ```python import requests url = 'https://photon.komoot.io/api/?q=salzburg&limit=2' response = requests.request('GET', url ) print(response) ```

## R ```R library(httr) library(jsonlite) url = "https://photon.komoot.io/api/?q=salzburg" res = GET(url) data = fromJSON(rawToChar(res$content)) print(data) ```

## JavaScript ```js const requestOptions = { method: 'GET' }; const url = "https://photon.komoot.io/api/?q=salzburg"; fetch(url, requestOptions) .then(response => response.text()) .then(result => console.log(result)) .catch(error => console.log('error', error)); ```

## QGIS with Python or debugging panel 

## API-Client [Hoppscotch](https://hoppscotch.io/) or [Postman](https://www.postman.com/) 

## GeoCoding APIs - [OpenCage](https://opencagedata.com/) - [openrouteservice](https://openrouteservice.org/) - [Photon](https://photon.komoot.io/) - [Nominatim](https://nominatim.openstreetmap.org/ui/search.html) - ...

## Routing APIs - [GraphHopper](https://docs.graphhopper.com/) - [openrouteservice](https://openrouteservice.org/dev/#/api-docs) - [OSRM (FOSSGIS instance)](http://map.project-osrm.org/about.html) - ...

## Overpass API OpenStreetMap data mining ([example](https://overpass-turbo.eu/s/1dhk)) 

## [Actinia API](https://actinia.mundialis.de/api_docs/) "processing of geographical data that uses GRASS GIS for computational tasks" 

## Austrian APIs - [overview on data.gv.at](https://www.data.gv.at/suche/?searchterm=&searchin=data&formatFilter_sub%5B%5D=api) - [sun position](https://www.data.gv.at/katalog/dataset/e04221bc-7309-48b8-bffd-77655c626b8d) - [elevation profile](https://voibos.rechenraum.com/voibos/voibos?name=profilservice&Beschriftung=Beispiel&Startkoordinate=125264,372182&Zielkoordinate=125286,372316&CRS=31287&Ueberhoehung=1&Stuetzpunktabstand=2&Hintergrund=geolandbasemap&Output=Profil,Lage,Tabelle) - [geocoding](https://srv.doris.at/solr/searchservice/search/all2/?q=Maxglan) - [elevation query](https://voibos.rechenraum.com/voibos/voibos?name=hoehenservice&Koordinate=-41390,228170&CRS=31254)

## Links - slides: [jakobmiksch.eu/talks/geo_api](https://jakobmiksch.eu/talks/geo_api) - [meggsimum GeoServer instance](https://services.meggsimum.de/geoserver/web/) - [meggsimum company](https://meggsimum.de/) - contact: [jakob@meggsimum.de](mailto:jakob@meggsimum.de)