[ncl-talk] Problem with plotting station data in DMS-coordinates

MeteoBB info at meteo-bb.de
Sun Feb 3 16:27:22 MST 2019

```Hi Dennis,

thx. Seems to be work fine except for cases where the lat or lon is in
western or southern hemisphere.
I added some code for this and so this is my final function for
conversion of DMS to DD:
(if this is incorrect, please tell me)

;========================================================================
function dms2dd(dms:string)
;========================================================================

local dms_str, degrees, MINUTES, minutes, dd, cminutes

begin

dms_str  = str_strip(dms)
degrees  = totype(str_get_field(dms_str, 1, "."), "float")
cminutes = tochar(str_get_field(dms_str, 2,"."))
minutes  = totype(tostring(cminutes(0:1)), "float")  ; 2 places only!

if (any(minutes.ge.60)) then
print("dms2dd: illegal minutes value >= 60")
exit
end if

dd = abs(degrees) + (abs(minutes)/60.0)
if (any(tofloat(degrees).le.0.0)) then    ; degrees in western or
southern hemisphere
dd = dd*(-1.0)
end if

return(dd)

end
;========================================================================

Am 24.01.2019 um 21:12 schrieb Dennis Shea:
>
> Well, of course, NCL [other languages also] would treat the following
> as 'real' numbers
> ===
>
> undef ("dm_to_deg")
> function dm_to_deg(DM:numeric)
> ;  DM: latitude or longitude: structure: mantissa.characteristic
> ;      Example: 54.41:  degrees.minute: mantissa=51, characteristic=41
> local delim, dm_str, mantissa, CHARACTERISTIC, characteristic, deg
>
> begin
>    delim  = "."
>    dm_str = tostring(DM)
>    mantissa       = totype(str_get_field(dm_str, 1, delim), typeof(DM))
>    CHARACTERISTIC = tochar(str_get_field(dm_str, 2, delim))
>    characteristic = totype(tostring(CHARACTERISTIC(0:1)),typeof(DM))
> ; 2 places
>    if (any(characteristic.ge.60)) then
>        print("dm_to_deg: illegal characteristic value >= 60")
>        exit
>    end if
>    deg = mantissa + (characteristic/60.0)
>    deg at long_name = "degree coordinates"
>    deg at NCL_tag    = "dm_to_deg"
>    deg at info       = "global locations in degrees: derived from dm"
>    return(deg)
> end
> ;========================================================================
> ;                       MAIN: dms ==> degrees_minute_second
> ;========================================================================
>
>   lat_dm  = 54.41                 ; not 'real' number, rather  (54° 41')
>   lat_deg = dm_to_deg(lat_dm)
>   print(lat_deg)
>   print("")
>   print("===============")
>   print("")
>   lon_dm  = 13.26                  ; not 'real' number, rather    (13°
> 26')
>   lon_deg = dm_to_deg(lon_dm)
>
>
> On Thu, Jan 24, 2019 at 9:54 AM MeteoBB <info at meteo-bb.de
> <mailto:info at meteo-bb.de>> wrote:
>
>     Hello,
>
>     i have station data with lat/lon-coordinates in DMS (degree,
>     minutes).
>     I suppose NCL/NCAR always want's decimal coordinates as input?
>     That's why my plotted data points appears at a wrong position.
>
>     Example (this is my data looks like):
>     lat = 54.41 (54° 41')
>     lon = 13.26 (13° 26')
>
>     I think I have to transform the coordinates from DMS to decimal,
>     to have:
>     lat = 54.68
>     lon = 13.43
>
>     Then the location will be placed correctly on map.
>
>     My question:
>     Just wondering - is there really no built-in procedure/function
>     for the conversion from DMS to decimal coordinates? I found
>     nothing about these stuff in the mailing lists or on the web.
>     Furthermore, I am irritated that the tick labels are DMS in my
>     example program (see at the end), but he expects decimal coordinates.
>     If there is no built-in function, has anyone a funtion to convert
>     DMS to decimal or a workaround?
>
>     Thanks a lot.
>
>     Regards,
>     Robert
>
>
>     begin
>
>       wks  = gsn_open_wks ("png","test")
>       res                        = True
>       res at gsnMaximize            = True
>       res at gsnFrame               = False
>       res at mpGridAndLimbOn        = True
>       res at pmTickMarkDisplayMode  = "Always"
>       res at mpMinLatF              = 54
>       res at mpMaxLatF              = 55
>       res at mpMinLonF              = 13
>       res at mpMaxLonF              = 14
>
>       res at mpGridSpacingF         = 0.25
>       res at mpGridLineThicknessF   = 2.0
>       res at mpGridLineColor        = "Gray30"
>       res at mpOutlineBoundarySets  = "AllBoundaries"
>       res at mpDataBaseVersion      = "MediumRes"
>       res at mpDataSetName          = "Earth..4"
>       res at mpGridAndLimbOn        = True
>
>       mkres                      = True
>       mkres at gsMarkerIndex        = 16     ; Filled circle
>       mkres at gsMarkerSizeF        = 0.008
>
>       plot   = gsn_csm_map(wks,res)
>       gsn_polymarker(wks,plot,13.26,54.41,mkres)
>       frame(wks)
>
>     end
>
>
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