Hi,
Apologies for an attachment to a list email, but I kept it small...
The attached image shows some Antarctic data (grounding line & ice shelf
extent) with a polygon overlayed.
I created the polygon by editing a text (csv) file with lat/longs:
x,y
150,-60
150,-85
255,-85
255,-60
I opened it in QGIS (CRS=EPSG:4326) & created a new polygon shapefile layer
(snapping to the points) to create a box defined by the same points.
Then I opened the Antacrctic layers (WFS from NSIDC
http://nsidc.org/cgi-bin/atlas_south in EPSG:3031 - Antarctic Polar
Stereographic)
I set the QGIS project CRS to a user defined one, same as EPSG:3031, but with
+lon_0=180 instead of 0 which gives a 180 up map instead of 0 up.
The map is displayed as in the attached image - a strange box is drawn to the
north of the box polygon, the eastern points & vertices do not appear - and if
the layer is editable, they cannot be clicked on as nodes.
If I swap the CRS to EPSG:3031, the inverted map renders the box better (no
extra box outside it) but the points are still rendered in a different location
to the polygon vertices - but they share the same coordinates.
I can usually work around 180 issues in QGIS by using longitudes in the 0-360
space, but it seems to me that there are some issues with QGIS working in a
polar projection across 180.
Does anyone know if there is a way to solve this, or is this an inherent
problem for now? In the short term I need to decide whether or not I can
progress with QGIS in the cross 180 polar space, or will need to find another
tool.
In the longer term, if this is an issue, I'd like to work with a developer to
resolve it - and may be able to fund (some of?) the work required.
Thanks,
Brent Wood
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