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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-FAMILY: ">Kathryn,</SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-FAMILY: "></SPAN> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN style="FONT-FAMILY: ">Just
thinking now … if you've got a vertical perspective (find the formulas for
vertical perspectives in section 1.3.17.2 of Guidance Note 7 Part 2 at
www.epsg.org) on a spherical earth, the horizon is a fixed number of grid units
from the center, i.e. the lat/lon of your geostationary satellite on the Earth,
which is (0,0) in grid units. <SPAN style="mso-spacerun: yes"> </SPAN>The
formulas in GN7-2 will help you compute that distance, but no matter. <SPAN
style="mso-spacerun: yes"> </SPAN>Just experiment until you find the
horizon by trial and error. <SPAN style="mso-spacerun: yes"> </SPAN>That
is, if (Northing^2 + Easting^2) > (fixed distance)^2, blank that point out.
<SPAN style="mso-spacerun: yes"> </SPAN>Now, this simplicity would not be
possible with an ellipsoidal Earth ...</SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-FAMILY: "></SPAN> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-FAMILY: ">Noel</SPAN></P>
<DIV> </DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: 'Calibri'; COLOR: #000000">Noel Zinn,
Principal, Hydrometronics LLC<BR>+1-832-539-1472 (office), +1-281-221-0051
(cell)<BR>noel.zinn@hydrometronics.com (email)<BR>http://www.hydrometronics.com
(website)<BR></DIV>
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<DIV> </DIV>
<DIV style="BACKGROUND: #f5f5f5">
<DIV style="font-color: black"><B>From:</B> <A title=kathryn.jablonski@noaa.gov
href="mailto:kathryn.jablonski@noaa.gov">Kathryn Jablonski - NOAA Affiliate</A>
</DIV>
<DIV><B>Sent:</B> Tuesday, August 13, 2013 11:00 AM</DIV>
<DIV><B>To:</B> <A title=proj@lists.maptools.org
href="mailto:proj@lists.maptools.org">PROJ.4 and general Projections
Discussions</A> </DIV>
<DIV><B>Subject:</B> Re: [Proj] Proj4 Projection Coordinates for
Geostationarysatellitedata</DIV></DIV></DIV>
<DIV> </DIV></DIV>
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style="FONT-SIZE: small; FONT-FAMILY: 'Calibri'; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-DECORATION: none; DISPLAY: inline">
<DIV dir=ltr>Hi Noel,
<DIV> </DIV>
<DIV>We set up the above definition from following the proj4 definition of
geostationary. We have also tried this string: </DIV>
<DIV>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. </DIV>
<DIV> </DIV>
<DIV>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</DIV></DIV>
<DIV class=gmail_extra><BR><BR>
<DIV class=gmail_quote>On Tue, Aug 13, 2013 at 10:43 AM, Noel Zinn (cc) <SPAN
dir=ltr><<A href="mailto:ndzinn@comcast.net"
target=_blank>ndzinn@comcast.net</A>></SPAN> wrote:<BR>
<BLOCKQUOTE class=gmail_quote
style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">
<DIV dir=ltr>
<DIV dir=ltr>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: 'Calibri'">
<DIV>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</DIV>
<DIV> </DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: 'Calibri'">Noel Zinn, Principal,
Hydrometronics LLC<BR><A href="tel:%2B1-832-539-1472" target=_blank
value="+18325391472">+1-832-539-1472</A> (office), <A
href="tel:%2B1-281-221-0051" target=_blank
value="+12812210051">+1-281-221-0051</A> (cell)<BR><A
href="mailto:noel.zinn@hydrometronics.com"
target=_blank>noel.zinn@hydrometronics.com</A> (email)<BR><A
href="http://www.hydrometronics.com"
target=_blank>http://www.hydrometronics.com</A> (website)<BR></DIV>
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style="FONT-SIZE: small; FONT-FAMILY: 'Calibri'; FONT-WEIGHT: normal; FONT-STYLE: normal; TEXT-DECORATION: none; DISPLAY: inline">
<DIV style="FONT: 10pt tahoma">
<DIV> </DIV>
<DIV style="BACKGROUND: #f5f5f5">
<DIV><B>From:</B> <A title=kathryn.jablonski@noaa.gov
href="mailto:kathryn.jablonski@noaa.gov" target=_blank>Kathryn Jablonski -
NOAA Affiliate</A> </DIV>
<DIV><B>Sent:</B> Tuesday, August 13, 2013 9:38 AM</DIV>
<DIV class=im>
<DIV><B>To:</B> <A title=proj@lists.maptools.org
href="mailto:proj@lists.maptools.org" target=_blank>PROJ.4 and general
Projections Discussions</A> </DIV>
<DIV><B>Subject:</B> Re: [Proj] Proj4 Projection Coordinates for Geostationary
satellitedata</DIV></DIV></DIV></DIV>
<DIV> </DIV></DIV>
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style="FONT-SIZE: small; FONT-FAMILY: 'Calibri'; FONT-WEIGHT: normal; FONT-STYLE: normal; TEXT-DECORATION: none; DISPLAY: inline">
<DIV>
<DIV class=h5>
<DIV dir=ltr>Thanks Janne.
<DIV> </DIV>
<DIV>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: </DIV>
<DIV> </DIV>
<DIV><IMG alt="Inline image 1"><BR></DIV>
<DIV>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. </DIV>
<DIV> </DIV>
<DIV>Thanks for the support!</DIV>
<DIV> </DIV></DIV>
<DIV class=gmail_extra><BR><BR>
<DIV class=gmail_quote>On Tue, Aug 13, 2013 at 3:12 AM, <SPAN dir=ltr><<A
href="mailto:support.mn@elisanet.fi"
target=_blank>support.mn@elisanet.fi</A>></SPAN> wrote:<BR>
<BLOCKQUOTE class=gmail_quote
style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">Hello,<BR><BR>we
just discarded all points outside any reasonable area.<BR>Another
possibility might be to draw a limiting line (or box)<BR>and move all
outside points to that..<BR><BR>Hope that helps?<BR><BR>Regards:
Janne.<BR><BR>----------------------------------------------------------------------------------------<BR><BR>Kathryn
Jablonski - NOAA Affiliate [<A href="mailto:kathryn.jablonski@noaa.gov"
target=_blank>kathryn.jablonski@noaa.gov</A>] kirjoitti:<BR>
<DIV>
<DIV>> I am trying to convert geographic coordinates (in degrees
east/north lat<BR>> lon) to projected coordinates in meters for
geostationary full disc data<BR>> (GVAR Goes East data from CLASS).
To do this, I tried using PyProj/ Proj4<BR>> and am running into errors
due to the off earth pixels in the corners.<BR>><BR>> This is the
proj4 string given:<BR>> projection_coords = Proj("+proj=geos
+h=35774290 +a= 6378137 +b= 6378137<BR>> +lon_0=-75 +units=meters
+no_defs")<BR>> ll_x, ll_y = projection_coords_geos( LL_y_deg, LL_x_deg,
inverse = False,<BR>> errcheck=True)<BR>>
'x=%9.3f y=%11.3f' % (ll_x,ll_y)<BR>> ur_x,ur_y =
projection_coords_geos( UR_y_deg, UR_x_deg, inverse =<BR>> False,
errcheck=True)<BR>> 'x=%9.3f y=%11.3f' %
(ur_x,ur_y)<BR>><BR>> For full disc geos data I am receiving incorrect
(1e30) values for the<BR>> extents and was wondering if anyone has ever
run into the same error or<BR>> have a suggestion to correct
this.<BR>><BR>> Also, for remapping GOES data, should the 'sweep axis'
be including in the<BR>> Proj string and set to 'y'?<BR>><BR>>
Thanks in advance for any suggestions!<BR>><BR></DIV></DIV>>
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