Hello,
I have an oracle georaster being accessed via the Image Mosaic JDBC plugin (version information below). The georaster is stored in EPSG:4326. I have an openlayers client with a tiled wms layer that displays the data in EPSG:900913.
The issue I am having is that the tiles requested by openlayers appear to have a slight overlap at the edges.
As an example the following two requests are for adjacent tiles (one just north of the other). In the northern tile there is a green area that stops just short of the bottom of the tile while in the southern tile the green area extends into the top of the tile slightly.
Northern tile
/geoserver/wms?LAYERS=nafi%3AFire%20Scars%20by%20Month%20Current&TRANSPARENT=TRUE&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&STYLES=&FORMAT=image%2Fpng&SRS=EPSG%3A900913&BBOX=14793316.704141,-1291480.0297266,14798208.67395,-1286588.059917&WIDTH=512&HEIGHT=512
(Attached as northern_tile.png)
Southern tile
/geoserver/wms?LAYERS=nafi%3AFire%20Scars%20by%20Month%20Current&TRANSPARENT=TRUE&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&STYLES=&FORMAT=image%2Fpng&SRS=EPSG%3A900913&BBOX=14793316.704141,-1296371.9995361,14798208.67395,-1291480.0297266&WIDTH=512&HEIGHT=512
(Attached as southern_tile.png)
So when viewed in openlayers it appears like:
(Attached as open_layers.png)
Note the green sliver at the bottom of the top green area.
This artifiact is not coming from the data itself, as can be seen by requesting the two areas together.
/geoserver/wms?LAYERS=nafi%3AFire%20Scars%20by%20Month%20Current&TRANSPARENT=TRUE&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&STYLES=&FORMAT=image%2Fpng&SRS=EPSG%3A900913&BBOX=14793316.704141,-1296371.9995361,14798208.67395,-1286588.059917&WIDTH=512&HEIGHT=1024
(Attached as combined.png)
Note that there is no gap/sliver in the bottom of the top green area.
You can see that the BBOXes share a common edge. The bottom of the northern tile (-1291480.0297266) is the same as the top of the southern tile (-1291480.0297266).
What could be causing this slight overlap?
I have also noticed that when zooming in and out there seems to be slight shifts in the position of the raster layer. This does not occur for any of the vector layers.
The layer is being styled using the following SLD:
<?xml version="1.0" encoding="ISO-8859-1"?>
raster_trans_50
Tile caching is disabled for this layer.
The georaster has an 8 bit cell depth and uses a pallette.
Version information:
Oracle: 11.2.0.1.0 (on Windows Server 2008 R2 Enterprise - 64 bit)
Geoserver: 2.9.0 (on RHEL 6.8 - 64 bit)
Running on: Apache Tomcat/7.0.70
JVM Version: Oracle Corporation: 1.8.0_91 (Java HotSpot™ 64-Bit Server VM)
Native JAI: Not installed
Native JAI ImageIO: Not installed
This is not our production setup, I have listed the above versions as this is what was used when producing the above examples. The problem originally occurred on an older version of Geoserver running in tomcat 7 on windows.
Thank you for your time.
Michael Pascoe
