[Qgis-user] QGIS reprojection broken?

[Nyall Dawson]

Hi Brent,

Try switching off simplification in the "layer properties" - "rendering"
tab. Does that help?

Nyall

On 08/08/2014 11:42 am, "Brent Wood" <pcreso at pcreso.com> wrote:
>
> 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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