[OpenLayers-Users] pixel units to lat/lon units & nexrad

[Scott Baker]

I was trying to do something similar to this when I first started - I 
asked here in the list about it too - but received no response. So I 
spent 3 months figuring it out myself... Correct me if I'm wrong, but I 
couldn't find any way to use gdal2tiles for anything other then a single 
map - always in pixel coordinates and not suitable for any sort of 
overlays.

It's a great method for creating a standalone OL viewer of a raster map 
but that's about it.

As soon as you want to get into mixing layers, overlaying stuff - etc... 
you will need a mapserver to do it.

I ended up with mapserver running and then implementing tilecache 
(mapserver is incredibly slow directly) then an OL display. The 
combination of the three is the only way I found to get nice looking 
maps and have floexibility enough to include raster, vector, and public 
data in OL.

You might get by if all your data is coming from other WMS servers by 
just using tilecache.

Again - I'm pretty new at this myself - but this, through months of 
trial and error, is the only solution I could find.


Wendell Turner wrote:
> I have tiled maps generated by gdal2tile.py which load into
> OpenLayers very nicely using units:'pixel'.  I would like to
> change the layout to lat/lon and am having trouble, and
> request assistance (I've flailed around with various options
> settings, but really don't know what I'm doing).
>
> Q1) The reason for doing this is to (hopefully) be able to 
> overlay nexrad weather by referencing a layer from
> http://columbo.nrlssc.navy.mil/ogcwms/servlet/WMSServlet/AccuWeather_Maps.wms
> Is this timely data?  How often is this data refreshed?  Is 
> there a better source for nexrad data?
>
> Q2) I assume that I need to change from pixel-units to
> lat/lon-units in order to layer the AccuWeather_Maps on the
> display, correct?
>
> Q3) Is gdal2tile.py still used in OL 2.6 (it seemed to be
> based on 2.4), or is there a better way to have OpenLayers
> generate the tiles?  Does it pre-generate them, or do it
> on-the-fly?
>
> Q4) Do I need to fully understand all of the extents vs.
> resoultion vs. maxResolution etc, or is there an easy way to
> capture the gdalinfo data from a GeoTiff file and import
> that into the options array needed by OpenLayers?
>
> I think OpenLayers is a terrific tool, I'm just not a
> cartographer (yet).
>
> Thanks,
>
> Wendell
>
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Scott W. Baker B.A.Sc
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