[GRASS-user] shapefile, TIGER, or what for a dlg that is stored in .e00 format

[Dylan Beaudette]

Hi,

Do you need to use this data for the generation of a DEM? Would it be
possible to use another source? seamless.usgs.gov is a great place to
get gridded elevation data for the USA. Interpolating from contours
should be a last resort.

Cheers,
Dylan

On Wed, Jul 8, 2009 at 6:42 PM, stephen sefick<ssefick at gmail.com> wrote:
> I tried this with points, lines and areas on the .e00 file
>
> v.in.e00 'file=/Users/sefick/Desktop/contours Folder/contours.e00'
> type=area vect=georgia_contours --overwrite
>
> importing areas......
>
> unable to open data <source cont>
> an error occured. Stop.
>
> what now?
>
> I didn't have any luck with the grid data - tried and gave up.
>
> thanks
>
> Stephen Sefick
>
> On Wed, Jul 8, 2009 at 7:38 PM, Nikos
> Alexandris<nikos.alexandris at felis.uni-freiburg.de> wrote:
>>
>> stephen sefick wrote:
>>
>>> I am trying to make a DEM from contour lines downloaded from here
>>> http://csat.er.usgs.gov/statewide/layers/contours.html
>>> I converted this to a shape file
>>
>> You don't need to convert it to  Shapefile. You can import vector .e00
>> files directly in GRASS using v.in.e00. Note that you need to have to
>> programs installed: "avce00" and "e00compr".
>>
>>
>>> reprojected it,
>>
>> why? from what to what CRS? Did you not create a location based on the
>> coordinate reference system in which the data are referenced? Did you
>> have any success with the "GRID" data, if of course you tried?
>>
>>
>>>  and then v.to.rast use=value and got out a raster with a range of 1
>>> to 1.
>>
>> That is so because the v.to.rast module expects from the user to define
>> the "value" incase you use the "use=value" parameter. If the user does
>> not define the "value" then "value=1" is taken as default. Please read
>> the respective manual(s) [1].
>>
>> I suppose that "v.to.rast use=val value=SomeValue" is not what you want.
>> Giving a fixed value to all of the vector features that will be
>> rasterized wont be useful if you want to play further with the data
>> (e.g. create a DEM as you mention above).
>>
>>
>>> How do I do this?
>>
>> --%<---code--%<---
>> # I downloaed the data you mention and did the following:
>> v.in.e00 contours.e00 vect=contours type=line
>>
>> # check attribute table
>> v.info -c contours
>>
>> v.info -c contours
>> Displaying column types/names for database connection of layer 1:
>> INTEGER|cat
>> INTEGER|UserId
>> INTEGER|FNODE_
>> INTEGER|TNODE_
>> INTEGER|LPOLY_
>> INTEGER|RPOLY_
>> DOUBLE PRECISION|LENGTH
>> INTEGER|CONTOURS_
>> INTEGER|CONTOURS_I
>> INTEGER|ELEV
>>
>> # match region ## I am unsure about the resolution (=look at the
>> original data resolution from which the contours derived)
>> g.region vect=contours res=SomeResolutionValue -pa
>>
>> # the last column is probably of your interest, so
>> v.to.rast use=val value=attr col=ELEV
>> --%<---code--%<---
>>
>> Perhaps you do not even need to rasterise. Have a look at v.surf.rst
>> [2]. Of course I am no expert with DEM's, v.surf.rst might not be what
>> you need.
>>
>> Kind regards, Nikos
>> ---
>>
>> [1] http://grass.osgeo.org/grass64/manuals/html64_user/v.to.rast.html
>>
>> [2] http://grass.osgeo.org/grass64/manuals/html64_user/v.surf.rst.html
>>
>>
>
>
>
> --
> Stephen Sefick
>
> Let's not spend our time and resources thinking about things that are
> so little or so large that all they really do for us is puff us up and
> make us feel like gods.  We are mammals, and have not exhausted the
> annoying little problems of being mammals.
>
>                                                                -K. Mullis
> _______________________________________________
> grass-user mailing list
> grass-user at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/grass-user
>