Spectrum Spatial (SSA/LIM)

Expand all | Collapse all

Spectrum Spatial Tiles wrongly reprojected

Jump to Best Answer
  • 1.  Spectrum Spatial Tiles wrongly reprojected

    Posted 05-20-2020 14:42
    Hello, I'm creating a new project that needs a fresh new basemap, which will be a Spectrum Tile, as usual. The raster to use is OS Miniscale. I have created the map and uploaded it successfully in the repository. The map looks good when loaded as a map, but once converted into a Tile, it reprojects: it stretches and deforms. Seems that for some reason is reprojecting to another coordinate system. But both the original and end coordinate systems are EPSG:27700.

    I have successfully created many maps using the same method, with different sources. Can't see what I am doing wrong. Does anybody have an idea of what could be the reason?

    I would like to include a couple of images but the form doesn't allow me, functionallity not working.

    ------------------------------
    Miquel Roy Sunyer
    Kirklees Council
    HUDDERSFIELD
    ------------------------------


  • 2.  RE: Spectrum Spatial Tiles wrongly reprojected
    Best Answer

    Posted 05-21-2020 20:53
    Edited by Duri Bradshaw 05-22-2020 07:13

    Hi Miquel,

    Do you have custom bounds set on the Tile?

    I have seen strange behaviour like you are describing when my bounds are not correct, sorry I cant tell you what they should be as I don't use epsg27700.

    I think the bounds need to be a square, but I'm not certain of this

    (maxX - minX) / (maxY - minY) = 1

    ------------------------------
    Duri Bradshaw
    Spatial IT Consultant
    Insight GIS
    ------------------------------



  • 3.  RE: Spectrum Spatial Tiles wrongly reprojected

    Posted 05-22-2020 07:14
    Hi Duri, thanks for the tip. The square bounds worked, but don't understand why. We've been using non-square bounds for other tiles and we never had this issue. Anyway, as long as it works, that's fine.

    Thanks,

    ------------------------------
    Miquel Roy Sunyer
    Kirklees Council
    HUDDERSFIELD
    ------------------------------



  • 4.  RE: Spectrum Spatial Tiles wrongly reprojected

    Posted 05-24-2020 17:30
    Hi Duri and Miquel,

    The documentation gives the following formula - tileHeight = (boundsHeight ÷ boundsWidth) × tileWidth - and gives a few examples of bounds where the 2:1 and 3:1 height:width tile ratios would be used.
    http://support.pb.com/help/spectrum/19.1/en/webhelp/Spatial/index.html#Spatial/source/Services/map_tiling/deployconfigure/howtileheightiscalculated.html

    The tool tip though in Spectrum states the bounds need to square. FWIW our bounds are configured as a approx 93km sided square for the relevant region within EPSG:28355.

    That doesn't really clear anything up, but maybe someone from the PB side can provide some more detail.

    ------------------------------
    William Dean
    Cairns Regional Council
    ------------------------------



  • 5.  RE: Spectrum Spatial Tiles wrongly reprojected

    Posted 05-28-2020 01:06
    Edited by Timothy Righetti 05-28-2020 01:14

    I still haven't discovered precisely how this fix works, but at least for myself in ESPG:28355 it's more than simply using square bounds.

    1. Our .ecw imagery to be tiled has the extent shown in QGIS calculated as:

    329000,5821000 : 356000,5850000 -> 27,000x 29,000y -> Using this causes incorrect tile location, mismatching the vector data

    2. In SSA, the only bounds to work without 'stretching' into the wrong location is:
    329000,5821000 : 356000,5848000 -> Which is equal to 27,000m x/y (square). The tiles show in the correct location, however it cuts of about 2km worth of imagery from the northern extent and is the only current workaround we have available.

    3. Seeing as the square bounds in step two work, I attempt to do a larger square bounds that doesn't cut the imagery off i.e. 30,000x 30,000y but I get the same projection error.  I've tried many combinations of square bounds, such as extending the Min X rather than Max X etc, to no avail.

    So there's obviously some specific trick at play here. As far as mine goes the trick is to use the 3 original MinX,MinY,MaxX and (if the original Y axis is larger than X) reduce the Max Y until it forms a square, which will obviously clip part of your tile extent




    ------------------------------
    Timothy Righetti
    Senior Spatial IT Business Analyst
    Nillumbik Shire Council
    Greensborough VIC
    ------------------------------



  • 6.  RE: Spectrum Spatial Tiles wrongly reprojected

    Posted 05-28-2020 02:40

    Hi Timothy,

    The Bounds I use for EPSG:28355 are

    MinX MinY MaxX MaxY
    -40867.905 5112643.474 3329926.909 8483438.288


    ------------------------------
    Duri Bradshaw
    Spatial IT Consultant
    Insight GIS
    ------------------------------



  • 7.  RE: Spectrum Spatial Tiles wrongly reprojected

    Posted 05-28-2020 03:30
    Thanks Duri,

    Unfortunately those aren't working for me either! I guess it's the workaround for now!


    ------------------------------
    Timothy Righetti
    Senior Spatial IT Business Analyst
    Nillumbik Shire Council
    Greensborough VIC
    ------------------------------