[GRASS5] Re: "default" datum parameters

[Alfonso Vitti]

Hello Markus and Paul,

I'd like to suggest to find a different word to replace "Default", 
"whole" is still not correct, at least for the rome40 case reported 
below. The paramters
towgs84=-225.000,-65.000,9.000
can "correctly" be applied only to the Sardinia island, as reported in:
http://earth-info.nga.mil/GandG/publications/tr8350.2/wgs84fin.pdf

 > ---
 > 4       Used in whole rome40 region
 >         (PROJ.4 Params towgs84=-225.000,-65.000,9.000)
 >         Default 3-Parameter Transformation (May not be optimum for
 >	  older datums; use this only if no more appropriate options
 >         are available.)

So in this case it should be something like "Used in Sardinia island".

Now, if I understand correctly, all the parameters stored in the file 
"datum.table" are parsed and presented to the user as in point 4 above.
This lead to the problem of choosing a right word which can not be 
"Default" and could be "whole" in all the cases where the parameters 
parsed can actually be used for the "whole" region.
If the rome40 case is the only with local parameters, and since the are 
more accurate parameters available for the Sardinia island (see choice 
n. 2 in the parameters list), perhaps the choice n.4 could be omitted, 
so the user can choose only between the first 3 options.

Regards,
Alfonso Vitti



> Message: 8
> Date: Fri, 31 Mar 2006 17:35:49 +0200
> From: Markus Neteler <neteler at itc.it>
> To: grass5 at grass.itc.it
> Subject: [GRASS5] Re: GRASS: "default" datum parameters
> 
> Hello Paul,
> 
> thanks for your efforts! It's good to know that datum stuff
> is no longer scattered around.
> 
> Here, for the record, the same test again:
> 
> ++++++++++++++++++++++++ Gauss Boaga, Italy ++++++++++++
> Please specify datum name
> Enter 'list' for the list of available datums
> or 'custom' if you wish to enter custom parameters
> Hit RETURN to cancel request
> 
>  >>rome40
> 
> 
> Now select Datum Transformation Parameters
> Please think carefully about the area covered by your data
> and the accuracy you require before making your selection.
> 
> Enter 'list' to see the list of available Parameter sets
> Enter the corresponding number, or <RETURN> to cancel request
> 
>  >>list
> 
> Number  Details
> ---
> 1       Used in Italy (Peninsular Part)
>         (PROJ.4 Params towgs84=-104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68)
>         Accuracy 3-4m
> ---
> 2       Used in Italy (Sardinia)
>         (PROJ.4 Params 
> towgs84=-168.6,-34.0,38.6,-0.374,-0.679,-1.379,-9.48)
>         Accuracy 3-4m
> ---
> 3       Used in Italy (Sicily)
>         (PROJ.4 Params towgs84=-50.2,-50.4,84.8,-0.690,-2.012,0.459,-28.08)
>         Accuracy 3-4m
> ---
> 4       Used in whole rome40 region
>         (PROJ.4 Params towgs84=-225.000,-65.000,9.000)
>         Default 3-Parameter Transformation (May not be optimum for older 
> datums; use this only if no mor
> e appropriate options are available.)
> ---
> 
> Now select Datum Transformation Parameters
> Please think carefully about the area covered by your data
> and the accuracy you require before making your selection.
> 
> Enter 'list' to see the list of available Parameter sets
> Enter the corresponding number, or <RETURN> to cancel request
> 
>  >> 1
> 
> 
> ++++++++++++++++++++++++ END ++++++++++++++++++++++++
> 
> Now the wording should be clear. Of course, the user *has*
> to think...
> 
> Thanks again
> 
>  Markus
> 
> 
> 
> 
> 

-- 
____________________________________________________________________________

"He who has imagination without learning has wings but no feet"

Department of Civil and Environmental Engineering
University of Trento
Via Mesiano, 77 - 38100 Trento (ITALY)

Alfonso Vitti
tel: +39 0461 88 26 08
fax: +39 0461 88 26 72

email: alfonso.vitti at ing.unitn.it
____________________________________________________________________________