Web Coverage Service (WCS) - A missing piece in INSPIRE?
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A MIG Workshop on WCS-based INSPIRE download services was hold in the Joint Research Centre (JRC) - Ispra, in October 2014. Advantages, benefits and issues when using this type of services were discussed during the event, together with use-cases and existing software support.
The workshop demonstrated that all operations required by the Download Service IRs can be mapped to the WCS 2.0 standard, and that using a WCS for providing coverage data provides a number of benefits and opportunities (depending on the supported WCS extensions), e.g.
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Data provision of model results (e.g. surfaces and grids) or multi-dimensional or multi-variable data through services, directly accessing to original data.
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Advanced download:
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Queries based on filters that are not trimming and slicing, e.g. corridor selection (calculate the exposure to air pollution along a route or the air temperature along flight corridors).
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(Server-side) advanced analyses (directly accessing the data), e.g. statistical analyses, interpolation between point values, aggregations (e.g. means, min/max, exceedances, etc.), time series analyses.
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Visualisation (for mapping purposes):
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An image coverage as-is.
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Using interpolation of point clouds.
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Using reclassification of range values.
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Using styling as defined by the user.
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Selecting a style provided by the server.
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The workshop also illustrated that further guidelines or best practices are needed for how to provide harmonised INSPIRE coverage data through the WCS.
MIG-T is currently drafting a proposal to open a MIG temporary sub-group on WCS (MIWP-07b), taking into account these outcomes to start working in this area. This will probably end up with an update of the INSPIRE Download Services technical guidelines, including the WCS option for coverages.
At the moment the only possibility to publish a raster data download service seems to be ATOM feed (predefined data set download service).
Please provide your opinion and experience on this topic:
- Do you think that WCS is a missing piece in INSPIRE?
- Which benefits / drawbacks do you foresee if WCS is used in the INSPIRE context?
- Any additional items to be discussed or treated by this group?
- Explain you own experience and best practice with the use of WCS (evaluation, use-cases, software utilized, etc.)
This will be a valuable input for the set-up of MIWP-07b.
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The INSPIRE MIG has decided to set up the new temporary sub-group on Extension of Download Service Technical Guidelines for Web Coverage Services (WCS) - MIG Action MIWP-7b
The main outputs of the sub-group will be:
Find more information in this piece of news:
https://themes.jrc.ec.europa.eu/news/view/31350/new-call-for-participation-mig-temporary-sub-group-on-extension-of-download-service-technical-guidelines-for-web-coverage-services-wcs-mig-action-miwp-7b
And also in the MIG platform:
https://ies-svn.jrc.ec.europa.eu/issues/2441
Expecting your valuable feedback and contribution!
At the Flemish hydrography in Belgium a WCS data portal Bathymetry is built up in order to deliver sounding grids with a resolution of 1 meter.
The formats used for downloading are GeoTIFF, BAG (Bathymetric Attributed Grid), CSV (XYZ text files), PNG and JPEG.
WCS seems very effective. Our PostgreSQL database with the spatial extender PostGIS has a data model based on the S-57 object/attribute catalog supplemented with our own internal attributes.
In addition to the grid coverage a GML file can also be downloaded with the surrounding polygon of the surface and the associated attributes.
We use the CARIS Spatial Fusion Enterprise software for our Data Portal Bathymetry.
We are now looking into the FME software to convert the GML with the S-57 objects/attributes into the INSPIRE data specification model.
Dear Marc,
Thank you very much for your input. This sounds like a good example of WCS implementation / use-case in the scope of the Elevation theme.
Can you point us to the data portal of your agency, where this WCS can be accessed?
Dear Jordi,
You will need to request a login by completing the registration form that you can find at the following URL:
http://bathy.agentschapmdk.be/index.php
After receiving a account you can log in and you can download with WCS a combined grid of our Belgian Continental Plat (150324_BELGIUM_BCP_DTM) with a resolution of 20 meter in geoTIFF, BAG, PNG, JPG or text/CSV in different Coordinate Reference Systems (EPSG code). Not only the coverage can be downloaded but also the metadata of the coverage in GML (not INSPIRE Compliant).
If you want to download more detailed bathymetric data (resolution 1m) you have to log in for a second time with the same login and password (login button see right upper corner).
There is also a help button in the right upper corner how to use the SFE Map Viewer.
http://bathy.agentschapmdk.be/spatialfusionviewer/documents/mapviewer/Map_Viewer_en.pdf
Greetings,
Marc
Thank you Marc,
I will have a look at let you know afterwards.
Jordi
Marc / Jordi,
Has there been any further discussion on this thread? I am wondering if there is any recommendstions on storage encodings for point cloud data sets e.g. LAS. I am particularly interested in the binary encoding recomendations (file or database) that work alongside WCS
Keiran
Dear Keiran,
At the moment, LIDAR data is explicitly excluded from the scope of the INSPIRE Technical Guidelines on Elevation. Hence, the specification does not include any recommendation on point cloud data storage.
However, as requested during the INSPIRE-KEN & TC #3 Workshop on Transformation of Coverage-based Data Themes and WCS by the representative of IGN-France (Dominique Laurent), I am going to open a new discussion topic regarding the need to reconsidering this aspect, e.g. cover LIDAR / Pount Cloud data in the Elevation Technical Guidelines.
Hopefully tomorrow!
Jordi
Hi Jordi,
Thank-you for the update. Point cloud data is also used in SONAR applications too, so is relevant to marine applications. You may be interested in the MIG-T proposal below which is dealing with 'unsupported' data formats.
Keiran
https://themes.jrc.ec.europa.eu/pages/view/44063/of-mf-data-in-non-supported-representations
Keiran / Jordi,
At the Flemish Hydrography point clouds are used for storage of SingleBeam and LiDAR data. In our Bathy Database TRITON the point clouds are converted into grids with a resolution of 1m, 5m, 10m or 20m. Those grids can be downloaded from our data portal Bathymetry in the formats BAG, GeoTIFF, JPEG and PNG with the associated metadata in GML. The SB point clouds in the Bathy DataBase can also be downloaded in text/CSV format, LiDAR data only in a grid format with a resolution of 1m.
Marc
Herby some questions and answer from PDOK (a Dutch SDI) regarding the working group “MIWP-7b: MIG temporary sub-group on Extension of Download Service”
No not really. The government who owns the data supplied us with Geotiff files and LAZ files. After putting the data in the database we build a WCS in Geoserver on the data. This is/was quite easy and we didn’t had problems. We use Geoserver 2.7.1.
Geoserver allows an end user to use a few output formats like Geotiff, image/png, text/plain etc.After having a look at the logging from last July, August and September (from a few of our elevation datasets) we received approximately 35.000 WCS (user) requests on those datasets. 91% percent choose GeoTiff and 8,5 percent choose image/tiff.
Last year we presented a very popular big (nationwide) elevation dataset via viewservices and via a WCS and a Atomfeed (ahn1 and ahn2). To not overload our infrastructure the decision was made to allow user to download the data (in parts) via Atomfeeds. Also we supplied a WCS without any limits regarding maximum amount of downloads (per request). After a while we experienced some troubles with our systems so we limited the reading and more important the maximum size of one (download) request to 200MB in Geoserver (see the picture below). After that our infrastructure didn’t experienced any more troubles.
In the above situation the data was very popular and we received many requests though. A few weeks ago we supplied another dataset (ahn3) which isn’t nationwide yet so not that popular (yet) We didn’t assign any limitations and so far we had no problems even though requests can be quite big (one is approximately 8725 MB). This is not preferred when there are many users though. Regarding to INSPIRE PDOK thinks there should be a limit.