[Qgis-user] Support for (wrong) GEOCOVER projection for S hemisphere in qgis

[Luigi Castro Cardeles]

Hi List,

i don't think QGIS allow raster reprojection. Maybe that's is your problem.

best regards
Luigi Castro Cardeles


2009/11/18 Agustin Lobo <alobolistas at gmail.com>

> No, what I was doing was different:
> I was setting the project to 18S (not 18N) with OTF reprojection, the
> raster to 18N
> and the vector layers got reprojected to 18S but the raster
> was not displayed.
> I was expecting the raster to be located in the S hemisphere because
> the coordinates are negative. In TNTmips, as the coordinates are negative,
> even if the raster CRS is set
> to 18N, the raster is displayed in the S hemisphere. Not sure if this
> is what qgis should do, though, as we are dealing with wrongly annotated
> raster layers: in UTM, S is S, not negative N.
>
> On the other hand, I assumed that if you set the project to 18N, then the
> vector layers would projected to the N hemisphere.
> But have tried defining the project as 18N as you say, used Coordinate
> capture to check lon,lat, and actually get correct lon,lat coordinates (in
> the S
> hemisphere). The vector layers are reprojected to
> 18, no matter the S or N, the original latitude correctly defines the
> hemisphere.
>
> So it works "your way", thanks!
>
> Agus
>
>
>
>
> Micha Silver wrote:
>
>> Hi Agus:
>> I am actually able to do just that. I also am using some Landsat GEOCover
>> images from below the equator, projected, as you say in UTM 39_N_.
>> I load the raster, set the project CRS to that (UTM Northern) projection,
>> and enable OTF projection. Then I can overlay vector layers, which are WGS84
>> Lon-Lat., and they are correctly located.
>>
>> It's usually not very helpful to say "works for me" but...
>> Anyway, HTH,
>> Micha
>>
>>
>> Agustin Lobo wrote:
>>
>>> The global set of Landsat images on GEOCOVER
>>> https://zulu.ssc.nasa.gov/mrsid/mrsid.pl
>>> is on UTM/WGS projection
>>> but with the Southern hemisphere tiles as UTM zones in the N with
>>> negative coordinates. For example, a tile that should be at 18S is
>>> actually 18N with negative coordinates
>>> ("Non-standard UTM definition: For the southern hemisphere, the GeoTiff
>>> files
>>>  contain positive zone numbers with negative northing coordinates")
>>>
>>> https://zulu.ssc.nasa.gov/mrsid/docs/GeoCover_circa_2000_Product_Description.pdf
>>>
>>> As we have some vector layers on geographic coordinates WGS84 and a
>>> Geocover tile for 18S,
>>> I've set the project as 18S, enabled CRS reprojection on the fly, and set
>>> the raster CRS to 18N. Unfortunately, QGIS does not display the raster,
>>> even
>>> selecting zoom to layer extent. (Using Mimas).
>>>
>>> This is probably not a problem of QGIS, the Geocover projection is just
>>> wrong,
>>> but would like to know if there could be a way to circumvent this problem
>>> to
>>> be able to use GEOCOVER tiles of the S hemisphere within QGIS.
>>> A way could be making a world file with the Georeferencer plugin, but
>>> perhaps
>>> there is a more general way.
>>>
>>> Thanks
>>>
>>> Agus
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