[Proj] Proj4 Projection Coordinates for Geostationary satellitedata

Tue Aug 13 09:00:20 PDT 2013

Hi Noel,

We set up the above definition from following the proj4 definition of
geostationary.  We have also tried this string:
Proj("+proj=geos +h=35786023 +a= 6378137.0 +b= 6356752.3141403561 +sweep=y
+lon_0=-75 x_0=-.151844 y_0=.151844 +units=meters +no_defs") and still get
the same error for the off earth data.

I get these as the output extents:[1e+30, 1e+30, 1e+30, 1e+30] and the
error given is this: RuntimeError: tolerance condition error

On Tue, Aug 13, 2013 at 10:43 AM, Noel Zinn (cc) <ndzinn at comcast.net> wrote:

>   Your graphic shows the earth profile as an ellipse, but your proj4
> string sets a and b to the semi-major axis of WGS84 (i.e. a sphere).  Why?
> -Noel
>
> Noel Zinn, Principal, Hydrometronics LLC
> +1-832-539-1472 (office), +1-281-221-0051 (cell)
> noel.zinn at hydrometronics.com (email)
> http://www.hydrometronics.com (website)
>
>  *From:* Kathryn Jablonski - NOAA Affiliate <kathryn.jablonski at noaa.gov>
> *Sent:* Tuesday, August 13, 2013 9:38 AM
> *To:* PROJ.4 and general Projections Discussions <proj at lists.maptools.org>
> *Subject:* Re: [Proj] Proj4 Projection Coordinates for Geostationary
> satellitedata
>
>  Thanks Janne.
>
> We did try drawing a limiting box inside the earth extents to get all
> valid data points within, and this works but cuts out data in the edges of
> the earth.  See the following image:
>
> [image: Inline image 1]
> We still need the data in between the drawn dotted line blue box and the
> edge of the earth.  The data values in the red shaded off earth areas are
> very large (2.14 E9) and these are the values that throw the error.  If you
> do discard the values in the light red, that is fine but it is throwing an
> exception instead, preventing us from proceeding forward.
>
> Thanks for the support!
>
>
>
> On Tue, Aug 13, 2013 at 3:12 AM, <support.mn at elisanet.fi> wrote:
>
>> Hello,
>>
>> we just discarded all points outside any reasonable area.
>> Another possibility might be to draw a limiting line (or box)
>> and move all outside points to that..
>>
>> Hope that helps?
>>
>> Regards: Janne.
>>
>>
>> ----------------------------------------------------------------------------------------
>>
>> Kathryn Jablonski - NOAA Affiliate [kathryn.jablonski at noaa.gov]
>> kirjoitti:
>>  > I am trying to convert geographic coordinates (in degrees east/north
>> lat
>> > lon) to projected coordinates in meters for geostationary full disc data
>> > (GVAR Goes East data from CLASS).  To do this, I tried using PyProj/
>> Proj4
>> > and am running into errors due to the off earth pixels in the corners.
>> >
>> > This is the proj4 string given:
>> >  projection_coords = Proj("+proj=geos +h=35774290 +a= 6378137 +b=
>> 6378137
>> > +lon_0=-75 +units=meters +no_defs")
>> > ll_x, ll_y = projection_coords_geos( LL_y_deg, LL_x_deg, inverse =
>> False,
>> > errcheck=True)
>> >     'x=%9.3f y=%11.3f' % (ll_x,ll_y)
>> >     ur_x,ur_y = projection_coords_geos( UR_y_deg, UR_x_deg, inverse =
>> > False, errcheck=True)
>> >  'x=%9.3f y=%11.3f' % (ur_x,ur_y)
>> >
>> > For full disc geos data I am receiving incorrect (1e30) values for the
>> > extents and was wondering if anyone has ever run into the same error or
>> > have a suggestion to correct this.
>> >
>> > Also, for remapping GOES data, should the 'sweep axis' be including in
>> the
>> > Proj string and set to 'y'?
>> >
>> > Thanks in advance for any suggestions!
>> >
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>>
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