Jack,
There were some issues with later versions of Mapserver and
mixing projections in the mapfile layers . We'd specify the LCC
projection for the map, which we're using for CONUS rasters/images
as Openlayers needs that to display georeferenced data, and then
specify lat/lon for the points layer within the mapfile. Early
versions of Mapserver automatically converted the layer's projection
to the map's projection, i.e. lat/lon to LCC. However, for some
reason which we hadn't figured out, later versions of Mapserver
didn't convert the lat/lon to the LCC projection for the resulting
image of point values (overlaid on top of grid images). Therefore,
we had to convert the lat/lon values to the GRIB native projection
so Mapserver would create an image of the point values in order for
it to be overlaid on top of the NBM image.
Now note that MDL doesn't currently feed the NBM 1D Viewer
(though I'm working on it ;) ). So you'd have to have to ask the
NBM 1D Viewer folks about their processes/conversions and data.
Personally, I use QGIS to check GRIB files, mostly for the entire
grid, though I occasionally use it to sample points too. If you're
just sampling at points, degrib's -P option can do that as well as
GDAL's gdallocationinfo. Note that degrib converts to English units
ny default and in most cases GDAL will convert to native GRIB
units. However, for temperatures, it may convert to Celsius.
Hope that helps. Dana and Kevin may chime in with other info.
Of course, let us know if you have other questions.
Dave M
Thanks Dana.
I was expecting to see lat/lon values there, vs the LCC
coordinates in meters, but perhaps it is done that way as
those JSON data and LCC coordinates are what is used
directly to feed NBM 1D ptvis view of NBM data?
Like here:
On a, sort of, related question, when I use the above
link, as I have been the last few days to explore NBM
Snow forecasts for Texas, and am working on
methods to consume that information in GIS
mapping, I'm coming across unit conversion
issues that has me scratching my head on if I'm
comparing 'apples to apples' to what's in NBM GRIB
files, what's on the WSUP and 1D viewer
pages, and how I need to convert the
GRIB data to match units/values.
For example, I make use of this GRIB file, which
contains the 6hrSnowAcccum data, for
different time length intervals, for the
ending time of 00UTC Jan 12.
When I look at the raw data, over KABI, which shows
up as 3.6" in the NBM 1D link above,
and this screen shot from the WSUP below, in
the raw data, I see a GRIB value of 0.142 in
the Weather and Climate Toolkit viewer I'm using.
As you've told me before, the units are encoded in the
GRIB files as the equivalent of mm, but the
Weather and Climate Toolkit appears to have
decoded the GRIB file and thinks it is in meters.
0.142 meters would translate to 5.59" which is
not the 3.6" depicted elsewhere.
Do you have a way to open that GRIB file, and sample
the raw data value at KABI, so I can confirm
the raw data in that file. Then, I can find
out if the error is in the Weather and
Climate Toolkit's handling of the GRIB, and the
units, if I'm looking at the proper field, so that I can
eventually do the proper translation of units as I
explore making use of these data in
developmental GIS mapping efforts.
--
Jack Settelmaier
Digital Techniques Meteorologist
NOAA/NWS, Southern Region HQ
Fort Worth, TX
Work: 682 703 3685
Cell: 817 966 0386
--
Jack Settelmaier Whole Story Uncertainty &
Probabilities Viewer Virtual Lab Forum http://vlab.noaa.gov/web/wsup/forums/-/message_boards/view_message/13265512VLab.Notifications@noaa.gov
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