Re: lat/lon to lambert outside of NCL (Jamie Lahowetz)

From: Jamie Lahowetz <jrl9262_at_nyahnyahspammersnyahnyah>
Date: Thu, 12 Feb 2009 12:50:30 -0600

Agreed. I will try my best (dont know what true latitude is) to describe
these terms. I will use the descriptions provided in thw w3lib and maybe the
confusion will diffuse.

NX NR POINTS ALONG X-AXIS = 349
NY NR POINTS ALONG Y-AXIS = 277
LA1 LAT OF ORIGIN (LOWER LEFT) = 1.0
LO1 LON OF ORIGIN (LOWER LEFT) = -145.50
RESOLUTION (RIGHT ADJ COPY OF OCTET 17) = 0
LOV - ORIENTATION OF GRID = -107.00
DX - X-DIR INCREMENT = 32463
DY - Y-DIR INCREMENT = 32463
PROJECTION CENTER FLAG = 0
SCANNING MODE FLAG (RIGHT ADJ COPY OF OCTET 28) = 64
LATIN 1 - FIRST LAT FROM POLE OF SECANT CONE INTER = 50.00
LATIN 2 - SECOND LAT FROM POLE OF SECANT CONE INTER = 50.00

Maybe this will help as well GRIB
1<http://www-imk.fzk.de/asf/kasima/aktuelles/grib/section2.html>.
only with w3lib I cant extract some of this data, as far as I know.

I am really trying to extract the data within the bounds: 43.5 39.0 -99.0
-93.5
What I am relly interested in now is converting the above bounds into
lambert grids then back to lat,lon. The lat,lon to lambert should match my
NCL grids (or close to) of 124 106 196 208 . A code that does this would be
great.

I have gotten it to work but I dont know how accurate the lat,lo are. Thanks
for all of the help.

>
> On Thu, Feb 12, 2009 at 7:43 AM, Lin,Jin-Sheng <jlin_at_deq.virginia.gov>wrote:
>
>> Jamie,
>>
>> I will have to do some search to see what the parameter conv is for.
>> However, I don't think it is the distance between grids. One of the
>> problems with map projection is that terminology is called differently in
>> different fields, it can get very confusing. For instance, in the example
>> in your e-mail, you have "lat of 1", "long of 1", "book results"
>> or "subbounds." I don't have a slightest idea what they are.
>>
>> Let's start from scratch and try this. You tell me what conversion
>> you would like to make and provide me with data and projection information
>> (projection centers, true latitudes, etc), and I will see what I can do.
>> This way we know we start with the same footing.
>>
>> Jin
>>
>>
>>
>> Jin-Sheng Lin
>> Regional Air Quality Modeler
>> Virginia Department of Environmental Quality
>> Air Division
>> 629 East Main Street, 8th Floor
>> Richmond, VA 23219
>> tel: (804)698-4412
>> e-mail: jlin_at_deq.virginia.gov
>>
>>
>>
>>
>> ------------------------------
>> *From:* deadpickle_at_gmail.com [mailto:deadpickle_at_gmail.com] *On Behalf Of
>> *Jamie Lahowetz
>> *Sent:* Wednesday, February 11, 2009 11:32 PM
>> *To:* Lin,Jin-Sheng
>> *Cc:* ncl-talk_at_ucar.edu
>> *Subject:* Re: lat/lon to lambert outside of NCL (Jamie Lahowetz)
>>
>> Thanks for your response. I do have a few questions about the code.
>>
>> what is the variable conv for? Is it the distance between grids?
>> I changed it around for F90 and I get NaN for the lats. The grib data
>> reports two 'true lats' but they are both the same. This could be the reason
>> why I get a NaN (division be zero maybe) How do you handle these situations?
>>
>> I have been messing with the w3fb12 included in the w3lib supplied (kind
>> of) by NCEP. It does well on lat/lon 2 lambert but is aweful the other way.
>> I also tried an equation I found in "map Projections - A Working Manual".
>> Results as such:
>>
>> lat of 1 = 1.0
>> lon of 1 = -145.0
>> lon of orientation = -107.0
>> lat secant1 = 50.0
>> lat secant2 = 50.0
>> spacing = 32463 meters
>>
>> subbounds within this domain: 43.5 39.0 -99.0 -93.5
>>
>> NCL grid # for bounds(respectively):124 106 196 208
>> Book results: 119 117 187 208
>>
>> One out of 4 is.... bad. I do admit that it could be me of course, I'm
>> only human. I do ask anyone who have a conversion script (any language not
>> just fortran) to try out these numbers and see what you get. I'm very
>> curious If there are any scripts out there that work better. Thanks before
>> hand, this forum is always helpful.
>>
>>
>>
>> On Wed, Feb 11, 2009 at 1:57 PM, Lin,Jin-Sheng <jlin_at_deq.virginia.gov>wrote:
>>
>>> Jamie,
>>>
>>> I have attached in this e-mail a fortran program we frequently use
>>> to convert different coordinate systems. There are two subroutines in the
>>> program: one is for UTM and lat/long conversion, and the other for Lambert
>>> and lat/long conversion. You only need the second subroutine to do what you
>>> described.
>>>
>>> Jin
>>>
>>>
>>>
>>> Jin-Sheng Lin
>>> Regional Air Quality Modeler
>>> Virginia Department of Environmental Quality
>>> Air Division
>>> 629 East Main Street, 8th Floor
>>> Richmond, VA 23219
>>> tel: (804)698-4412
>>> e-mail: jlin_at_deq.virginia.gov
>>>
>>>
>>>
>>>
>>
>>
>>
>> --
>> Jamie Ryan Lahowetz
>> University of Nebraska - Lincoln
>> Graduate Student - Geosciences
>> 402.304.0766
>> jrl9262_at_huskers.unl.edu
>>
>
>
>
> --
> Jamie Ryan Lahowetz
> University of Nebraska - Lincoln
> Graduate Student - Geosciences
> 402.304.0766
> jrl9262_at_huskers.unl.edu
>

-- 
Jamie Ryan Lahowetz
University of Nebraska - Lincoln
Graduate Student - Geosciences
402.304.0766
jrl9262_at_huskers.unl.edu

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Received on Thu Feb 12 2009 - 11:50:30 MST

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