[GRASS-user] using data from unstructed grid, triangle mesh

[Jaime Carrera]

Hi John:

You can import the triangular mesh as a vector file by first importing the nodes with v.in.ascii and by creating a three column table (as you have three water elevation values) linked to the id number of each node. To create the triangular mesh run v.delaunay.

Jaime

John Overton <jd3 at renci.org> escribió: Hi,
I'm new to GIS topics, so please forgive if this is an obvious question.

I have some coastal data that is in the form of a triangle mesh where 
the triangles are of different sizes.  The triangles are subdivided the 
closer they get to the coast.  The smallest distance between two 
vertices in the mesh is about 90ft(27m).  Each vertex in the triangle 
set holds the water height at that location.  Each vertex also has a 
lat/lon associated with it.

I want to get this data into a GIS system like GRASS.  I have not seen 
features in any GIS system so far that allow an unstructed grid of data 
like this to be easily read in.  Please let me know if I am not correct 
on this, because the ideal situation would be to enter the data as is.  
However, if I am correct that I will have to transform the data, do any 
of you have strong ideas about the way this should be done?
First, I thought about using shapefiles, because the data is in a 
polygon format right now. Each triangle really has 3 different water 
height values, though, so I thought shapefiles would not work since they 
seem to describe a polygon that maps one value to the area it spans.
Next, I found the GEOtiff format.  For this, I imagine I would have to 
transform the triangle mesh into a raster format, and include a 
projection.  Right now there are lat/lons for each data point.  Is there 
any advice on how to accomplish this?  One drawback that I see to this 
is the enormous amount of raster data I would need when the resolution 
is 27m between data points where the water meets the coast.  If I used 
this approach, I thought I could create several different geotiff files 
strategically placed to cover the NC coast.  Is there a certain size, 
that hits a sweet spot with GIS systems?

Please help!

Thanks,
John Overton
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