Unsupported file format error in getCoverage()

[dgobb]

Hello,
I am trying to download Digital Elevation data from a Geoscience Australia WCS but encounter errors in getCoverage() and describeCoverage() as indicated in the code below.

In particular, calls to getCoverage return
Error: [rast] cannot open this file as a SpatRaster: C:\Users\xxx\AppData\Local\Temp\RtmpqQM7w4/1_138.9,-33.4,139,-33.3.tif
and
Warning message: `C:\Users\xxx\AppData\Local\Temp\RtmpqQM7w4/1_138.9,-33.4,139,-33.3.tif' not recognized as being in a supported file format. (GDAL error 4)

wcsServerURL <- "http://services.ga.gov.au/gis/services/DEM_SRTM_1Second/MapServer/WCSServer"
epsg_WGS84 <- "EPSG:4326"
epsg_GDA94 <- "EPSG:4283"

bbox <- OWSUtils$toBBOX(xmin=138.9, xmax=139.0, ymin=-33.40, ymax=-33.30)

wcs <- WCSClient$new(url = wcsServerURL, "1.0.0", logger = "INFO")

caps <- wcs$getCapabilities()       # get the WCS server capabilities
caps$getCoverageSummaries()     # review to find the CoverageId, in this "1"
wcs$describeCoverage("1") 

The last call returns
Error in as.vector(x, "character") : cannot coerce type 'environment' to vector of type 'character'

cov <- wcs$capabilities$findCoverageSummaryById("1", exact = TRUE)   # identify the coverage we want
cov$getDimensions() 
ras <- cov$getCoverage(bbox=bbox, crs=NULL)

The last call returns
Error: [rast] cannot open this file as a SpatRaster: C:\Users\xxx\AppData\Local\Temp\RtmpqQM7w4/1_138.9,-33.4,139,-33.3.tif
In addition: Warning message:
`C:\Users\xxx\AppData\Local\Temp\RtmpqQM7w4/1_138.9,-33.4,139,-33.3.tif' not recognized as being in a supported file format. (GDAL error 4)

Other variants are similarly unsuccessful

ras <- cov$getCoverage(bbox=bbox, crs=epsg_WGS84)
ras <- cov$getCoverage(bbox=bbox, crs=epsg_GDA94)

Any assistance would be greatly appreciated. I suspect something unusual with the response received from the WCS server.

Additionally, it took me a long time to establish how to find the coverageID, and I suggest that the getCoverageSummaries() function could be made more prominent in the documentation.

Regards
David

[dgobb]

I should add that I am able to access the coverage in QGIS without problems. The raster properties shows:

Server Properties:
WCS Version 1.0.0
Title DEM_SRTM_1Second
Get Coverage Url http://services.ga.gov.au/gis/services/DEM_SRTM_1Second/MapServer/WCSServer?

Coverages
Name (identifier)1
Title DEM SRTM 1 Second
WGS 84 Bounding Box | 112.9998611140000548,-44.0001389004616996 : 153.9998611133509883,-10.0001389009999500

[eblondel]

The WCS 1.0 requires more parameters to work, making it not really user friendly (why WCS 2 was designed). You have to give HEIGHT and WIDTH parameters. These are not set by default behind the request done by ows4R. QGIS should be applying some default values or compute them based on the bounding box.

You can try this:

ras2 <- cov$getCoverage(bbox = bbox, width=1000, height=1000)

I note your remark on getCoverageSummaries() and indeed doc should be improved on this.

[dgobb]

Hi Emmanuel, and thanks for your response.

This suggestion does allow a SpatRaster to be retrieved from the WCS server, although getCoverage() now displays "Start tag expected, '<' not found".

I note that the grid resolution of the returned raster are dependent on the provided height and width. So I will need to calculate the appropriate size for the grid resolution. That is clunky but will work for now I think. Is there any way to query the native resolution of the coverage? That data is not found, for example, in getDimensions()

Thank you!

[eblondel]

I'm also receiving "start tag" message. I get this in other service, I'm investigating why.

For the grid resolution, it's true it's not convenient at all to provide height/width in WCS 1.0 which is a bit primitive compared to higher versions. The pixel limits can be found in WCS 1.0 description:

desc = cov$getDescription() desc$domainSet$spatialDomain$RectifiedGrid$limits

The getDimensions is introduced with WCS 2, where dimensions (spatial, and other than spatial) are explictely defined. It doesn't apply to WCS 1

The calculation of the proper grid resolution is something I had in mind to integrate to avoid users having to specify heigh/width. If you want I can have a look and integrate that calculation within the code.

[eblondel]

@dgobb i've fixed the same issue of "Start tag expected, '<' not found" (see #135) and implemented a solution for above height/width in #134. If you can reinstall and try it. Now you just have to specify your bbox and the ows4R will take care of setting width/height parameters

[dgobb]

Thank you @eblondel. That is very helpful! I have run a preliminary test and it is working well. However I will do some further checking/verification in coming days and let you know if I encounter any issues.