[Spam/Pourriel] [GRASS-dev] Re: query vector points x,y

[Patton, Eric]

I'm not sure why, but how much precision do you need? If your projection
units are in meters, you can't get meaningful precision greater than a
decimeter anyway. Does it make sense to give coordinates for a position to 6
decimal places if the units are meters? Is your input data that precise?
Keep in mind that 6 decimal places is giving a precision of 1/10,000th of a
millimeter! 

~ Eric. 

-----Original Message-----
From: grass-dev-bounces at grass.itc.it
To: Maciej Sieczka
Cc: grass-dev at grass.itc.it
Sent: 9/27/2006 8:16 AM
Subject: [Spam/Pourriel] [GRASS-dev] Re: query vector points x,y

 (...)
>> Indeed, if I enter the command
>> v.to.db -p map=mymap type=point opt=coor column=dummy_x,dummy_y,dbl_3
>>or
>> v.to.db -p map=mymap type=point opt=coor column=dummy_x,dummy_y
>> I receive the rows
>> cat|x|y|z
>> and not any other field  (for example dbl_3).
>>Damiano
 (...)
> Well, you are asking for opt=coor and that's what you are getting. Now
> you'd have to combine the v.to.db opt=coor output with db.execute
output.
>
> Sorry.
>
> Maciek
OK, but then I think it is better to use v.out.ascii for this purpose!
 v.out.ascii print coordinates with high precision, while v.to.db gives
only
 a couple of decimals after floating  point. Why?
 Damiano

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