[R-sig-Geo] gps file->WGS84->NAD83 Alaska stateplane zone 1

[Barry Rowlingson]

On Sat, Jul 14, 2012 at 10:31 AM, Robert J. Hijmans <r.hijmans at gmail.com> wrote:
> Dave,
>
> What I would do is project the data in ArcGIS, and and then read them into
> R and use proj4string to get the projection from that object. Then use that
> proj4string to project, in R, the lon/lat data and see if they now match
> up. I just did that and I think you espgs code in incorrect. I would
> generally avoid these opaque codes, certainly when sending a question to
> the list. For you epsg code, I get:
>
>> proj4string(bear414_nad83)
> [1] " +init=epsg:26931 +proj=omerc +lat_0=57 +lonc=-133.6666666666667
> +alpha=323.1301023611111 +k=0.9999 +x_0=5000000 +y_0=-5000000 +ellps=GRS80
> +datum=NAD83 +units=m +no_defs +towgs84=0,0,0"
>>
>
> For ArcGIS I get something else (the value of alpha):
>
> [1] "+proj=omerc +lat_0=57 +lonc=-133.6666666666667
> +alpha=-36.86989764583333 +k=0.9999 +x_0=5000000 +y_0=-5000000 +datum=NAD83
> +units=m +no_defs +ellps=GRS80 +towgs84=0,0,0"
>>

The first alpha is 360 plus the second alpha (to 8 decimal places), so
if they are rotational parameters they should be equivalent...

Barry