[Proj] Oblique Cyl Eq Area
woklist at charter.net
Thu Jul 7 14:02:00 EDT 2005
On Jul 7, 2005, at 12:31 PM, Gerald I. Evenden wrote:
> First. "trillion" seems to have a ambiguous definition in Kdict so
> I am not sure about
> your what you mean here. Is it greater or lesser than a
> gazillion? :-) sorry about my humor.
I think trillion is a standard thing - the next step beyond a
> Secondly, I am not sure I am aware of the +ellps=sphere option.
> When I try it on lproj
> I get a segmentation fault which I am looking into at this moment.
> Note any undefined
> ellipsoid name creates the same error.
'proj -le' lists all the ellipoids supported, and sphere is there
('Normal sphere', r=6370997). I have no seg faults with it. I get a
more graceful bail with unknown ellipsoids.
System info: Mac OS 10.4.1 (GCC 4), proj.4 4.4.9.
> One thing I will note is that I am more familiar with specifying
> the two points in an west
> to east orientation so that point 1 would be 22.5,90 and point 2
> -45,180 so that I am
> not sure that reversing the order will not generate unexpected
I first noticed it in MAPublisher (the GIS plugin for Illustrator),
with these same results. The difference of specifying it W-E vs. E-W
just rotated it different, same trillions issue. E-W looked better,
but either way north is not vertical.
I just tried it by setting both lat's to 0, theoretically making it a
normal cylindrical eq area along the equator, centered at 135deg E -
still in the trillions. I tested a cyl eq area with lon_0=135 and
anyways, low budget on this project, and the client doesn't really
care, so I'll just go with an azimuthal.
> There is definitely one bug item here and you will hear more from
> me in the near
sure. if not for this project, it would still be nice to have this
projection option working.
> On Thu, 2005-07-07 at 10:14 -0500, William K wrote:
>> Sorry to repeat, but I need to know if anyone has any ideas on
>> this: I want to set up a map with the Oblique Cylindrical Equal
>> Area projection (ocea). I couldn't find much info on parameters
>> needed and the effects of them. From what I found in the USGS
>> projections book I need two points for the oblique line (lat_1,
>> _2, lon_1, _2). Simple enough. Yet I get projected coordinates in
>> the trillions! It's not an easting/northing problem - I get +/-
>> trillions around the center of the projection. this is what I used
>> (Australia/SE Asia region): proj +proj=ocea +ellps=sphere
>> +lat_1=-45 +lat_2=22.5 +lon_1=180 +lon_2=90 (I tried ellps=WGS84
>> also) Changing the distance between the oblique points seems to
>> affect the projection a bit - instead of at the limits of the area
>> of interest, if I make them say 1/10 of that apart, the
>> coordinates go down by up to a trillion. Anyone have any definite
>> info on setting up this projection? If it's normal, what do those
>> large numbers really mean (if not meters)? Did I miss a parameter?
>> ----- William Kyngesburye <kyngchaos at kyngchaos.com> http://
>> www.kyngchaos.com/ "History is an illusion caused by the passage
>> of time, and time is an illusion caused by the passage of
>> history." - Hitchhiker's Guide to the Galaxy
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William Kyngesburye <kyngchaos at kyngchaos.com>
"History is an illusion caused by the passage of time, and time is an
illusion caused by the passage of history."
- Hitchhiker's Guide to the Galaxy
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