How to Solve "Points to Area failed" problem (fwd)

Ms.Blanca Shulan Huang blanca at
Sun Jan 19 17:10:23 EST 1997

---------- Forwarded message ----------
Date: Mon, 30 Dec 1996 12:25:50 -0500
From: Pat Luther <pluther at>
To: blanca at
Subject: Re: How to Solve "Points to Area failed" problem

Hi Blanca:

I am trying to determine the easiest way to solve your problem.  There are
several ways to clean up your data, some are just easier than others.
I realize the problems of cleaning up other people's data, and duplicate
data problems.

Did you loose all of your label points or just a few ?

Do you have access to ARC/INFO ?  If you do , it might be easier to clean
up the maps in ARC/INFO, rather than GRASS.

Do you intend to use the data in GRASS as raster data ?  If you do not
need the vectors for anything in GRASS, the easiest way to do this is
to convert the data to a GRID in ARC/INFO.  Then change the files to 
image files with the GRIDIMAGE command.  GRASS will read an image file.
This should eliminate the "lost labels" problem.

There are several ways to get rid of the duplicates.  In ARC/INFO, you 
can search for duplicate arcs and get rid of the duplicates.  In GRASS,
you can set your region to coordinates that excludes the duplicate data,
create a new layer using r.mapcalc (oldmap = newmap) with the unwanted
data cut off, then do r.patch to put all the files together.

It is much easier (for me) to work with raster data.

If you do not have access to ARC/INFO, or if you want to have the files in
vector format in GRASS, I will have to do a bit more research and thinking
on your problem.  Please let me know.  I could also work on your files
myself, if you like.  

Good luck & happy new year !  Where are you located ?

Pat Luther

>Hi Pat Luther,
>After I import data from Arc/Info, then I did the command to
>the vector map which is generated from the process.  If I saw
>many "points to areas failed" message, how and what should I do to
>correct this result?
>The reason that I need to correct the error is: if I ignore these error,
>and go ahead to convert the vector file to raster file, the resulted
>raster file will not show those areas failed to be converted.  Then I
>will get an imcomplete raster map.
>I use to try using v.digit command to LABEL the "problem" areas which
>missed their label points, but I can't make it right.  How can label an
>area which is formed by many single lines?
>Please help me to solve this problem.  I am in the process of converting
>a big city map from Arc/Info data to GRASS.  And I encounter many
>problems.  One of them is data duplication.
>The city map data is stored in the Arc/Info system, and was input by
>eight people.  Somehow during the data input process, some portion of
>one people's job is duplicated with other co-worker's job.  So after I
>converted these eight sets of maps to GRASS, and tried to patch these
>eight single pieces of maps together to be a complete city map, I found
>I must cut off the duplicate portions first before I apply the v.patch
>So I cut off the duplicate protions by using v.digit command, then I
>apply the v.patch command to patch maps together.  The outlook of the
>resulted vecter map looks correct, only some pieces of areas lost their
>label points due to the "points to area failed" message.
>Blanca Huang
Pat Scarbrough Luther		"Your dream is the gift of 
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