[Proj] Oblique Cyl Eq Area

[William K]

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  
billion, 1,000,000,000,000.

> 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  
> results.
>
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  
that's fine.

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
> future.
>
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>
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