NEW - Petascope supports WMTS request

[Bang Pham Huu]

The WMTS serves a single tile of a single layer of a map. Unlike WMS, there is no
specified way to request a server to combine and return a map tile with information
coming from more than one layer in a single fetching process. 

In general it has 2 mandatory requests:

• GetCapabilities. Example: ​https://sampleserver6.arcgisonline.com/arcgis/rest/services/Toronto/ImageServer/WMTS?service=WMTS&version=1.0.0&request=getcapabilities

The big difference compared to WMS is, each Layer needs to be linked to at least on of TileMatrixSet. For example:

<TileMatrixSetLink>
     <TileMatrixSet>setInEPSG:4326</TileMatrixSet>
</TileMatrixSetLink>
<TileMatrixSetLink>
     <TileMatrixSet>setInEPSG:32633</TileMatrixSet>
</TileMatrixSetLink>

And a TileMatrixSet in a typical CRS has a set of TileMatrix elements.
Each TileMatrix element contains the 2D matrix of geo XY axes per layers' pyramid level in the CRS.
Each element in the 2D matrix of TileMatrix is called Tile and is accessed via indices: tileRow and tileCol.

For example:

<TileMatrixSet>
    <ows:Identifier>BigWorldPixel</ows:Identifier>
    <ows:SupportedCRS>urn:ogc:def:crs:OGC:1.3:CRS84
    </ows:SupportedCRS>
    <WellKnownScaleSet>urn:ogc:def:wkss:OGC:1.0:GlobalCRS84Pixel
    </WellKnownScaleSet>

    <!-- Base level -->
    <TileMatrix>
        <ows:Identifier>10000m</ows:Identifier>
        <ScaleDenominator>33130800.83133142</ScaleDenominator>
        <TopLeftCorner>-180 90</TopLeftCorner>
        <TileWidth>640</TileWidth>
        <TileHeight>480</TileHeight>
        <MatrixWidth>7</MatrixWidth>
        <MatrixHeight>5</MatrixHeight>
    </TileMatrix>
    <!-- pyramid member level 2 -->
    <TileMatrix>
        <ows:Identifier>20000m</ows:Identifier>
        <ScaleDenominator>66261601.66266284</ScaleDenominator>
        <TopLeftCorner>-180 90</TopLeftCorner>
        <TileWidth>640</TileWidth>
        <TileHeight>480</TileHeight>
        <MatrixWidth>4</MatrixWidth>
        <MatrixHeight>3</MatrixHeight>
    </TileMatrix>
    ...
</TileMatrixSet>

• GetTile. Example: ​https://sampleserver6.arcgisonline.com/arcgis/rest/services/Toronto/ImageServer/WMTS?service=WMTS&version=1.0.0&request=gettile&layer=WorldTimeZones&style=default&tileMatrixSet=default028mm&tileMatrix=13&TileRow=2990&TileCol=2289&format=image/png

Here, one needs to specify extra parameters (see Annex H in the document ​https://portal.ogc.org/files/?artifact_id=35326 for the formula to convert tile indices to layer's bounding box):

• tileMatrixSet: which TileMatrixSet is used (e.g. global CRS:4326 or native CRS EPSG:32632)
• tileMatrix: which TileMatrix is used (e.g. the pyramid member is selected)
• TileRow: Row index of the selected tile in the TileMatrix
• TileCol: Column index of the selected tile in the TileMatrix