[Proj] request help with Lambert Conic Conformal (2SP)

[Rick Graves]

Mikael and Carl,

Maybe there is a problem with the Oregon shape files, or maybe I made an incorrect assumption about the contents.

The Oregon redistricting web site is down for me at the moment:

www.leg.state.or.us/redistricting/

But the Oregon shape files are available here:

http://www.srrproject.org/resources/redistricting-shapefiles/


(Click on Oregon to get the link.  If you do not instantly know which one is Oregon, you can hover the mouse and a tip will display telling which state is under the pointer.  Oregon is on the West coast just North of California.)

The zip for Oregon includes two sets of files, Congressional_Districts.* and Congressional_Area_Changes.*. 

I assumed that I should go with the latter file.

I ran diff against the two .prj files, and there is no difference.

However, I just now discovered that the contents of the shapefiles are radically different.  Here are the bounding boxes:

Congressional_Districts

(183987.16863517463, 88653.9580052495, 2345137.542322829, 1677526.0958005222)


Congressional_Area_Changes

(427663.998031497, 172986.72867454588, 1005007.5570866163, 1488902.549212602)


Sorry for being a beginner, but is there something I should know to do with these two files?  Or should I be asking Oregon what is the deal?

Thanks,

Rick



________________________________
 From: Mikael Rittri <Mikael.Rittri at carmenta.com>
To: PROJ.4 and general Projections Discussions <proj at lists.maptools.org> 
Sent: Thursday, August 16, 2012 6:42 PM
Subject: Re: [Proj] request help with Lambert Conic Conformal (2SP)
 

Carl,
In fact, I don't think you are missing anything. 

I made a quick back-of-an-envelope calculation - not using
proj, just a plain calculator - starting with the projection
origin, assuming 111120 meters per degree of latitude,
and 111120 * cos(lat) meters per degree of longitude.  

For the test point, I got 

Easting = 1408985 ft
Northing = 2341613 ft. 

That's close enough to your (Carl's) result, with my simple method. 

I may have made a mistake, but Rick: could you double-check your expected coordinates - I am pretty sure they are wrong. 

Regards,

Mikael Rittri
Carmenta
Sweden
http://www.carmenta.com

16 aug 2012 kl. 05:30 skrev "Carl Godkin" <cgodkin at gmail.com>:



>
>
>On Wed, Aug 15, 2012 at 8:00 PM, Rick Graves <gravesricharde at yahoo.com> wrote:
>
>Hey,
>>
>>
>>The good news is that Oregon is the last one I need to get working.  The bad news is I do not have it working yet.
>>
>>
>>Here is the metadata from the .prj that I got from the state:
>>
>>
>>PROJCS["NAD_1983_Oregon_Statewide_Lambert_Feet_Intl",
>>GEOGCS["GCS_North_American_1983",
>>DATUM["D_North_American_1983",
>>SPHEROID["GRS_1980",6378137.0,298.257222101]],
>>PRIMEM["Greenwich",0.0],
>>UNIT["Degree",0.0174532925199433]],
>>PROJECTION["Lambert_Conformal_Conic"],
>>PARAMETER["False_Easting",1312335.958005249],
>>PARAMETER["False_Northing",0.0],
>>PARAMETER["Central_Meridian",-120.5],
>>PARAMETER["Standard_Parallel_1",43.0],
>>PARAMETER["Standard_Parallel_2",45.5],
>>PARAMETER["Latitude_Of_Origin",41.75],
>>UNIT["Foot",0.3048]],
>>VERTCS["NAD_1983",
>>DATUM["D_North_American_1983",
>>SPHEROID["GRS_1980",6378137.0,298.257222101]],
>>PARAMETER["Vertical_Shift",0.0],
>>PARAMETER["Direction",1.0],
>>
>>
>>I initialized proj as follows:
>>
>>
>>proj +proj=lcc +lon_0=-120.5 +lat_0=41.75 +lat_1=43.0 +lat_2=45.5 +x_0=1312335.958005249 +y_0=0.0 +units=ft
>>
>>
>>I assume something is not right.
>>
>>
>>
>>
>
>
>I think there are two things wrong:  
>1. Your false easting is here given in feet while I believe proj always wants meters.  The number is about 400000m.  (See http://trac.osgeo.org/proj/wiki/GenParms).
>2. You didn't include an ellipsoid or datum so I'm surprised that proj worked at all since I get an error without +datum=NAD83 or +ellps=GRS80.
>
>
>However, correcting both of those, I get  X=2344859.57 ft, Y=1434192.31 ft, which isn't what you want either.  
>
>
>Now I want to know what I am missing!  Let's hope someone cleverer than me answers.
>
>
>carl
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