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@grass.itc.it
To: Maciej Sieczka
Cc: grass-dev@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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You're perfectly right about practical meaning, but I have a theoretical interest;
another issue is that for a strange reason I may want to use kilometers as units, so meaningful centimeters are at distant decimal places!
What do you think?
Damiano
----- Original Message ----- From: "Patton, Eric" <epatton@nrcan.gc.ca>
To: "'Damiano Triglione '" <damiano.triglione@polimi.it>; "'Maciej Sieczka '" <tutey@o2.pl>
Cc: <grass-dev@grass.itc.it>
Sent: Wednesday, September 27, 2006 2:50 PM
Subject: RE: [Spam/Pourriel] [GRASS-dev] Re: query vector points x,y
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@grass.itc.it
To: Maciej Sieczka
Cc: grass-dev@grass.itc.it
Sent: 9/27/2006 8:16 AM
Subject: [Spam/Pourriel] [GRASS-dev] Re: query vector points x,y
(...)
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 -p gives
only
a couple of decimals after floating point. Why?
Damiano
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