[GRASS-user] custom projection

[Markus Neteler]

ramaraju wrote on 09/06/2007 10:47 AM:
> Hi,
> I am working on a mineral potential mapping project using satellite,
> ground geological, geophysical, geochemical data in the Mahabubnagar,
> Nalgonda districts of Andhra Pradesh. I am using grass as a module in
> the QGIS. When I checked the projections availble, I could not find
> the modified everest datum of 1956. 

GRASS uses the PROJ4 software which supports Everest 1956:

cs2cs -le | grep -i everest
  evrst30 a=6377276.345    rf=300.8017      Everest 1830
  evrst48 a=6377304.063    rf=300.8017      Everest 1948
  evrst56 a=6377301.243    rf=300.8017      Everest 1956
  evrst69 a=6377295.664    rf=300.8017      Everest 1969
  evrstSS a=6377298.556    rf=300.8017      Everest (Sabah & Sarawak)

The definition is also present in GRASS:

GRASS 6.3.cvs (nc_spm_06):~ > grep -i ever $GISBASE/etc/ellipse.table
# Everest 1830, India
# everest                                       a=6377276.345  
e=.0066378466
everest         "Everest 1830, India"           a=6377276.345   f=1/300.8017
evrst30         "Everest 1830, India"           a=6377276.345   f=1/300.8017
# Everest 1948, W. Malaysia and Singapore
evrst48         "Everest 1948"                  a=6377304.063   f=1/300.8017
# Everest 1956, India
evrst56         "Everest 1956, India"           a=6377301.243   f=1/300.8017
# Everest 1969, W. Malaysia
evrst69         "Everest 1969, W. Malaysia"     a=6377295.664   f=1/300.8017
# Everest (Sabah & Sarawak), Brunei and E. Malaysia
evrstss         "Everest Sabah and Sarawak"     a=6377298.556   f=1/300.8017
# Modified Everest (from elist.html from Peter H. Dana, cited from DMA 1987
# everest_m     "Modified Everest"              a=6377304.063  
b=6356103.039
everest_m       "Modified Everest"              a=6377304.063   f=1/300.8017
# Everest (Pakistan)
everest_p       "Everest (Pakistan)"            a=6377309.613   f=1/300.8017

When selecting the ellipsoid, use 'list' to get the list or enter
directly 'evrst56'.


> And also I could not
> figure out the setting of coordinates to latitude and longitude.
> Kindly help me in this regard
>   
Please take a look at the available documentation:
http://grass.itc.it/gdp/tutorials.php
http://grass.itc.it/gdp/books.php

Markus

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ITC -> dall'1 marzo 2007 Fondazione Bruno Kessler
ITC -> since 1 March 2007 Fondazione Bruno Kessler
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