Hi,

Unfortunately the question relates directly to using the WMTS service in 
MapExtreme which is developed by Pitney Bowes (who also own MapInfo and 
Confirm).

After investigating I have pretty much decided it is more a client issue as so 
far as I can tell the bounding box of the layer is changing at each zoom level. 
The top-left coordinates are moving so I can't see what else could be causing 
it. I assume this is why it is jumping in the GeoServer OpenLayers preview as 
well as it may be configured to use the top-left anchor.

My working theory is that MapExtreme is assuming that the bounding box is the 
same at all levels rather than recalculating it at each zoom level based on the 
information provided by the WMTS getCapabilities statement. Might be completely 
wrong but I suspect it may be a development request to PB if I'm correct. In 
fairness; the shift is only a few meters at the detailed level but it is still 
significant if you are trying to be accurate; our gully locations appear to be 
moving around on the road / pavement as a result.

If you have an interest; I'm not sure why you would voluntarily research 
MapExtreme; but if you do, the layer bounding box is set to 0,0,700000,1300000 
but this is the bounding box as calculated by MapInfo 17 (also has the same 
behaviour) and MapExtreme:
CoordSys Earth Projection 8, 79, "m", -2, 49, 0.9996012717, 400000, -100000 
Bounds (4.53547443948e-11, 0.313325276111) (760926.343337, 1521853)

You can see that the y coordinate is expanded to 1,521,853 which is a around 
200,000 meters away from the bounding box of the data. My understanding is that 
this is because the gridset has been expanded for mathematical reasons but that 
the data should still be in the right place.

Anyway, I'll stop there as it is unlikely to be a GeoServer issue; more likely 
a MapExtreme or GWC issue.
If anyone does have a work around then I'd love to hear it though.
Cheers,
Paul

-----------------------------

Message: 3
Date: Thu, 7 Feb 2019 20:07:44 +0000
From: Phil Scadden <[email protected]>
To: "[email protected]"
<[email protected]>
Subject: Re: [Geoserver-users] Gridset question
Message-ID:
<sycpr01mb5005ace89fd204c36f5e1aafc8...@sycpr01mb5005.ausprd01.prod.outlook.com>

Content-Type: text/plain; charset="us-ascii"

This rings some distant bells, though not with that particular EPSG (I'm in 
antipodes). I have vague memory of needing to set a tile origin somewhere. 
First step would be to isolate whether your issue is with geoserver or the 
browser client. (my memories of this are with openlayers but I switched to 
leaflet some time ago).
Can you look at the getmap request that browser is issuing and see whether the 
image being sent matches the bbox being requested. If so, then geoserver is off 
the hook and the problem is with the tileset management in the browser client. 
If it doesn't match, then problem is with geoserver. You say "cached content" - 
are you explicitly connected to a GWC cache or tileset, or is this from 
integrated GWC where you have seeded tiles? If you turn caching off, does the 
problem persist?

From: Paul Wittle via Geoserver-users <[email protected]>
Sent: Friday, 8 February 2019 01:54
To: '[email protected]' 
<[email protected]>
Subject: [Geoserver-users] Gridset question

Hi,

Does anyone know why my base mapping is moving when I preview the cached 
content in British National Grid (EPSG:27700)?

Please see the attached screenshot.

It doesn't do this in web Mercator projection. If you try to zoom in using this 
gridset the you end up in a completely different point (because the map centre 
is shifting) whilst if you scroll in on other projections the map centre 
remains constant.

It seems to have a minimal shift if I use the WMTS in QGIS but if I use it in 
MapInfo Confirm then the shift is more pronounced.

Best Regards,

Paul Wittle
GIS Developer
Insight, Intelligence & Performance

County Hall
Dorchester
Dorset. DT1 1XJ
Tel: 01305 228473
E mail: [email protected]<mailto:[email protected]>

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