v.proj more questions

[Admin. scarab J.M. ROQUES 5322]

Sue Huse , REGIS , UC Berkeley wrote:

...  We have
been going in the other direction (SP to UTM) and we needed to
create a brand new UTM location under GRASS4.1.  This made the
later version of the PROJ_INFO, which I then copied back over the
old one in our main location.  I think it is the "a" and "es" that
were missing.

Our current PROJ_INFO looks like:
        name: UTM
        proj: utm
        ellps: clark66
        a: 6378206.4000000004
        es: 0.0067686580
        zone: 10

and our State Plane (California) looks like:
        name: State Plane
        proj: lcc
        a: 0.63782064e+07
        es: 0.6768657997291094e-02
        x_0: 0.6096012192024384e+06
        y_0: 0
        lon_0: 122dw
        lat_0: 37d40'n
        lat_1: 39d50'n
        lat_2: 38d20'n

I believe that these work for us.


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Hello everyone,

after reading these discussions on projection transformation to/from UTM from/t
o State Plane, I realised that I will have to face the same problems soon.
Here in France, we generally use a Lambert conical conform representation (I am
 not sure of my english translation), based on the 30° parallel (where the proj
ection cone is tangent to the earth) and, as far as i know, using the 1880 Clar
ke ellipsoide.


As I am not sure of the State Plane projections used in the US does someone can
 tell me

a: if "lcc" in the Proj field of State Plane file means
"lambert conical conform" (or whatever better translated)

b: if i may use the "ellps" field with something like clark1880 or if i will ha
ve to put the right values for a and es along with my local origins.

c: if there is a mean to "add" a homothetic correcting factor

d: finally, if point a: is relevant, what is the exact meaning (or where will i
 find it) of the long_0, lat_0, lat_1, and lat_2 fields; (validity zone limits 
for the lat_0 and lat_2, center for long_0 and lat_1 ? or is lat_0 the base par
allell ?)

more generally where can i find a good documentation about projections supporte
d by Grass4.1 (last updates) ?