[R-sig-Geo] projection of degrees to North_Pole_Lambert_Azimuthal_Equal_Area

[Caroline Keef]

Dear all,

Ultimately I want to overlay a grid of points in degrees to polygons in a shapefile with projected coordinates.  However to do this I think I need to get them both on the same geographical system.  I'm trying to do this by taking the degrees and projecting them.  I've tried both project in the proj4 library, and mapproject in the mapproj library.  The answers I'm getting are very wrong.  The bit I'm struggling with most is finding out which parameters I actually need to input to these functions.  The R helpfiles don't give any information on this.  I've looked at http://www.remotesensing.org/geotiff/proj_list/lambert_azimuthal_equal_area.html and guessed but it doesn't seem to work.  However it's entirely possible I'm not understanding what I'm doing given the polygons of the shapefile seem to be rotated 90 degrees (North is towards the left in ARCmap), but given I only need to do an overlay this doesn't really matter.  What's most worrying is that when I change the input parameters in project the outputs don't change.

Can anyone help?

Thank you

Caroline


The shapefile was created in ARC and according to the .prj the details of the projection are

PROJCS["North_Pole_Lambert_Azimuthal_Equal_Area",
GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",
SPHEROID["WGS_1984",6378137.0,298.257223563]],
PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],
PROJECTION["Lambert_Azimuthal_Equal_Area"],
PARAMETER["False_Easting",0.0],
PARAMETER["False_Northing",0.0],
PARAMETER["Central_Meridian",0.0],
PARAMETER["Latitude_Of_Origin",90.0],
UNIT["Meter",1.0]]

According to ARC map the coordinates of Mumbai should be (roughly) 7048812, -2172723 the answers I get are

mapproject(x=72.83,y=18.975,proj="azequalarea")
$x
[1] 0

$y
[1] -0.8214892

$range
[1]  0.0000000  0.0000000 -0.8214892 -0.8214892

$error
[1] 0


project(xy=c(72.83,18.975),"+proj=laea +lat_0 = -90 +lon_0=0 +x_0=0 +y_0 = 0")
        [,1]    [,2]
[1,] 7197711 2590300
>        [,1]    [,2]

> project(xy=c(72.83,18.975),"+proj=laea +lat_0 = 0 +lon_0=0 +x_0=0 +y_0 = 0")
        [,1]    [,2]
[1,] 7197711 2590300

http://www.jbaconsulting.co.uk/
 
JBA Consulting
South Barn
Broughton Hall
Skipton
North Yorkshire
BD23 3AE
United Kingdom
http://www.jbaconsulting.co.uk/?q=nce-winner-2010
t: +44 (0)1756 799919 | f: +44 (0)1756 799449 
 
JBA is a Carbon Neutral Company. Please don't print this e-mail unless you really need to.
This email is covered by JBA Consulting's http://www.jbaconsulting.co.uk/emaildisclaimer.
 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://stat.ethz.ch/pipermail/r-sig-geo/attachments/20101117/6118ecba/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/gif
Size: 5104 bytes
Desc: not available
URL: <https://stat.ethz.ch/pipermail/r-sig-geo/attachments/20101117/6118ecba/attachment.gif>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/gif
Size: 3793 bytes
Desc: not available
URL: <https://stat.ethz.ch/pipermail/r-sig-geo/attachments/20101117/6118ecba/attachment-0001.gif>