> Hi John,
> Our documentation needs to be beefed up for configuring data on curvilinear grids. We'll get that in there asap.
>
> Finding the right set of I,J indices to correspond to a subset of longitude/latitude space takes some doing for curvilinear grids, and the best way to do that involves making a map file as if you were planning to offer regridding to a rectilinear grid, as outlined here,
> http://ferret.pmel.noaa.gov/LAS/documentation/installer-documentation/adding-curvilinear-data/configuring-las-to-regrid-curvilinear-data-to-rectilinear-grids
>
> Whether you add the option to do that regridding or not, the Ferret scripts can use that mapping file to find the right subset of the grid to show when zooming in XY. (what it does is described in this Ferret FAQ: How can I plot a subset of my curvilinear data? http://ferret.pmel.noaa.gov/FERRET_17sep07/FAQ/custom_plots/subsetting_curvi_data.html)
>
> So, create a map file with a resolution similar to what's in your curvilinear grid - for global curvilinear grid that's 400x200 points, we might use a 1-degree grid in x and y. Or as in your case, a fine grid over a small region of the globe, we'd make a grid defined with delta-x and delta-y being small fractions of a degree. The map file takes some time to compute but this only needs to be done once; and you save the dataset in a location where your server can use it.
>
> Configure this map file in as curvi_coord_mapfile, and the map variable as curvi_coord_mapvar. For instance, one I have looks like this; in the xml configuration for a dataset:
>
> <datasets>
> <Fdepths name="Ocean Model" url=""moz-txt-link-freetext" href="http://porter.pmel.noaa.gov:8380/thredds" target="1">http://porter.pmel.noaa.gov:8380/thredds
> /dodsC/GOMFD_RECENT">
>
> <!-- Default properties for this dataset -->
> <properties>
> <ferret>
> <curvi_coord_lon>LON</curvi_coord_lon> <!-- curv. coords -->
> <curvi_coord_lat>LAT</curvi_coord_lat> <!-- curv. coords -->
> <lon_modulo>0</lon_modulo>
> <curv_lon_min>-98.162</curv_lon_min>
> <curv_lon_max>-78.042</curv_lon_max>
> <curv_lat_min>17.991</curv_lat_min>
> <curv_lat_max>30.734</curv_lat_max>
> <curvi_coord_mapfile>/home/porter/data/my_las_data/map_01deg.nc</curvi_coord_mapfile>
> <curvi_coord_mapvar>map</curvi_coord_mapvar>
>
> </ferret>
> </properties>
>
> <variables>
> ...
>
>
> On 6/10/2010 5:20 PM, John Maurer, IV wrote: Hi All,
> We're very happy to see support for curvilinear grids in LAS7, but I've noticed a sporadic glitch when using zoom to explore the resulting curvlinear map plots. About half the time, when I zoom into a region containing data the resulting plot has either no data (just an empty map with coastlines and gridlines) or only some data (for instance, just the bottom half of the image has data). As an example, you can try our WRF model output at:
>
> http://oos.soest.hawaii.edu/las/getUI.do?dsid=id-7b24ef7324&catid=id-7b24ef7324&varid=Tair-id-7b24ef7324&plot=XY_zoomable_image&view=xy
>
> (Due to another problem, select any date but the first one: May 14th.) Try zooming in to the region surrounding the Big Island (the biggest island, towards the southeast of the archipelago) and you will likely notice that the top half of the plot is missing data. Other zoom regions display other unexpected results.
>
> Would love to have this resolved. Many thanks!
> Cheers,
> John Maurer
> Hawaii Ocean Observing System (HiOOS) |