[GRASS-user] Measuring Stream Lengths

[Rich Shepard]

On Sat, 30 Jan 2010, Dylan Beaudette wrote:

> Where did these data come from? It sounds like they were generated outside
> of GRASS. Can you describe the structure of this 'streams' dataset, and
> possibly how it was made?

Dylan,

   They're from the Oregon Geospatial Data Center. The state works strictly
with ESRI products under windoze. I'll send you the metadata pdf if you want
it.

> 1. segments with cat numbers, see v.category
> 2. an attribute table attached to this vector
> 3. stream names (?) populated in one of the columns, possibly with
> v.digit, or v.what
> 4. create a new column for the segment lengths
> 5. populate this column, v.to.db

   Here's the top of lotic.sql which I used to populate the SQLite table:

PRAGMA foreign_keys=OFF;
BEGIN TRANSACTION;
CREATE TABLE lotic (
   llid  TEXT,
   name TEXT,
   gnisNum TEXT
);
INSERT INTO "lotic" VALUES('1173558419005','','0');
INSERT INTO "lotic" VALUES('1173558419012','','0');
INSERT INTO "lotic" VALUES('1173593419067','','0');
INSERT INTO "lotic" VALUES('1173594419068','','0');
INSERT INTO "lotic" VALUES('1173804418848','','0');
INSERT INTO "lotic" VALUES('1173809419594','','0');
INSERT INTO "lotic" VALUES('1173817419323','','0');
INSERT INTO "lotic" VALUES('1173850419296','','0');
INSERT INTO "lotic" VALUES('1173857419343','','0');
INSERT INTO "lotic" VALUES('1174094419475','','0');
INSERT INTO "lotic" VALUES('1174103419484','','0');
...
INSERT INTO "lotic" VALUES('1175170420086','Rock Creek','1135566');
INSERT INTO "lotic" VALUES('1175178419964','','0');
etc.

   The 'llid' column is the lat/long of the head of each reach. There is one
additional column with another ID number that I did not import because it's
redundant to the gnisNum.

   Not much to work with, but I suppose that most folks who use these data do
digital cartography more than spatial analyses.

Rich