OGC SensorThings API

[ndevilleBE]

Dear,
I'm testing the use of the TerriaMap application to connect to an OGC SensorThings API.

I tested two approach in parallel, one with the table API and one with the GeoJSON but I'm not yet happy with the result. I manage to get only one feature on the map, but I'm struggling to create the Chart with the time-series result. The issue I guess is that the result is nested so the application has trouble linking them.
Do you have an example of the best approach to display fixed station observations (such as the URL in the example below) or even a moving measuring platform using the OGC SensorThings API?
Thanks

{
      "name": "OGC SensorThings",
      "type": "group",
      "members": [
        {
          "type": "geojson",
          "name": "STA geojson output",
          "id": "123456",
          "url": "https://sensors.bgs.ac.uk/FROST-Server/v1.1/FeaturesOfInterest(17)?$expand=Observations($select=resultTime,%20result)&$top=100&$resultFormat=GeoJSON",
          "defaultStyle": {
                  "time": {
                    "timeColumn": "resultTime"
                  },
                  "chart": {
                    "xAxisColumn": "resultTime",
                    "lines": [
                      {
                        "yAxisColumn": "result",
                        "name": "test"
                      }
                    ]
                  }
            }
        }
      ]
    }

[ndevilleBE]

Another test, which looks more promising for fixed station is to display the feature and then plot the chart in the featureinfotemplate when one station is selected.
The problem with this approach is that Terria does not recognize the phenomenonTime column as a time column...
The data can be downloaded as CSV as shown in the example but could also be read directly from the API as such:
https://sensors.bgs.ac.uk/FROST-Server/v1.1/FeaturesOfInterest(49)/Observations?$select=phenomenonTime,result&$top=100

Any idea?
Thanks
```

{
      "type": "geojson",
      "name": "STA geojson output",
      "id": "123456",
      "columns": [
        {
          "name": "phenomenonTime",
          "type": "time"
        },
        {
          "name": "result",
          "type": "scalar"
        }
      ],
      "url": "https://sensors.bgs.ac.uk/FROST-Server/v1.1/FeaturesOfInterest?$resultFormat=GeoJSON",
      "featureInfoTemplate": {
        "template": "<table><tbody><tr><td>Type</td><td>Station</td></tr><tr><td>Value</td><td>{{id}}</td></tr><tr><td>Data for station {{id}}</td><td><chart sources='https://sensors.bgs.ac.uk/FROST-Server/v1.1/FeaturesOfInterest({{id}})/Observations?$select=phenomenonTime,result&$top=100&$resultFormat=CSV' column-names='Time,Signal' column-units='Date,Watts' y-column='result'></chart></td></tr></tbody></table><p>Sample data only</p>",
        "showFeatureInfoDownloadWithTemplate": false
      }
    },

[zoran995]

I am not sure if data in this format can be used for visualizing the feature info time chart, but I will check with the team.
Some ideas in the meantime:

• the best path forward would be adding support for sensor things API by creating a sensor things API catalog item. It is a standard format so it should be possible to add it similarly to SOS we already support. This was actually already requested in support for sensorthingsapi #6746 but there was no work done on it and it still not got on our roadmap. If the community is interested in contributing something like this we will be happy to review
• Create a proxy where sensor observation results will be split by feature with the same identifier and each feature will have observation results with time

[na9da]

I agree with Zoran here that the ideal approach would be to write a connector for SensorThings.

Your second example is almost there but like you found out Terria fails to automatically recognize the column type as time. It currently does this by testing if the column name has date or time at word boundaries using a regex. The regex doesn't work for the camelCase phenomenonTime. Ideally it should then try to guess the type from the column values which it doesn't do now because parsing as date values could be expensive.

I hacked the regex to see how the chart would look, here's a screenshot. If this is something you are interested, I can create a PR with a fix for the dataset.

[ndevilleBE]

hello @na9da ,
I'm not a developer so I can't write a new connector for SensorThings. But I believe the regex improvement you suggest is a nice improvement that is worth implementing so yes please, do a PR!

[ndevilleBE]

Hello @na9da ,
Any update on this topic?
Thanks

[na9da]

Sorry @ndevilleBE , I haven't got a chance to create a PR yet. Hopefully I can look at it next week.