[GRASSLIST:8214] error in gnomonic projection - ?

[Milan Salek]

Hello,

I have some difficulty with transformation from/to gnomonic projection
 which I found in 'my' area and repeated in Spearfish training dataset.
I have spent some
time dealing with it but did not find any solution.

For example, I set up a new location spearfish_gnom with following 
parameters(for faster calculation I chose coarser resolution than orig.
Spearfish dataset): 

$cat PROJ_INFO:
name: Gnomonic
proj: gnom
a: 6379000.0000000000
es: 0.0
f: 0.0
lat_0: 44.4600000000
lon_0: -103.8500000000

$cat DEFAULT_WIND:
proj:       99
zone:       0
north:      5000
south:      -30000
east:       20000
west:       -2000
cols:       220
rows:       350
e-w resol:  100
n-s resol:  100
top:        1
bottom:     0
cols3:      1
rows3:      1
depths:     1
e-w resol3: 1
n-s resol3: 1
t-b resol:  1

I reprojected elevation.dem from spearfish to spearfish_gnom and found 
that there was a considerable (evident) shift in NS (y) direction of 
about  20 minutes (20'). EW direction is OK. The same results were 
on other area in Europe. 

In case the problem is between the keyboard and my chair I put the 
r.proj command:

GRASS 6.0.1 (spearfish_gnom):~ > r.proj input=elevation.dem 
location=spearfish mapset=PERMANENT output=elevation

I work on Mandrake 10.1, proj 4.4.9. The proj itself converts the 
projections OK. 

Do you have any suggestion?

Best regards 

Milan Salek