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

GRASS GRASS user
1

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, reprojected it, and then v.to.rast
use=value and got out a raster with a range of 1 to 1. How do I do
this? If you require any more information please tell me and I can
give it to you. Thanks for any help.

Stephen Sefick

--
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

2

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

3

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@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

4

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@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@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

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