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
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Timothy Righetti
Senior Spatial IT Business Analyst
Nillumbik Shire Council
Greensborough VIC
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Original Message:
Sent: 05-21-2020 20:53
From: Duri Bradshaw
Subject: Spectrum Spatial Tiles wrongly reprojected
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
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Duri Bradshaw
Spatial IT Consultant
Insight GIS
Original Message:
Sent: 05-20-2020 14:42
From: Miquel Roy Sunyer
Subject: Spectrum Spatial Tiles wrongly reprojected
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.
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Miquel Roy Sunyer
Kirklees Council
HUDDERSFIELD
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