Chris,
Sounds like an interesting project!
You should be able to extract a traverse with large numbers
of points (in the thousands) from a vector line with a large
number of vertices (again in the thousands).
I just tried this, with a line segment containing about 2,000
vertices, and wrote it out to a XYZ traverse file with 10,000
points, and it worked fine.
Here are a couple of notes that may help:
- First, get your traverse in as a vector overlay, in ERV
format (not ArcInfo coverage format as that format limits
the number of vertices in a vector)
- Call up annotation, and make sure the vector is displayed
- Open the traverse window, then select your line
- Click on the "save to file" in the traverse window, select
the number of points to write. A text file will be generated.
If you run into problems:
- When I tried it, the traverse window would not *display*
the full traverse once I exceeded a 1,000 vertices or so,
but it was quite happy writing the full traverse out to the
file.
- Make sure your vector is a polyline not a polygon
- Try breaking the vector into 3 or 4 stages, each with less
than 10,000 or so vertices
- There should not be any real limits to the number of points
you write out to the traverse file, but if you run into problems
try a smaller number to start with.
As a final note:
The number of vertices along the traverse is a different number to
the number of points written to the output traverse XYZ file. The
vertices related to the complexity of the line path, where as the
points relate to the number of sample made along the line (regardless
of how many vertices it has).
Hope this helps, and let me know how you get on.
Cheers
Mike
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Christopher Ferro
Sent: Wednesday, 29 May 2002 10:49 PM
To: [EMAIL PROTECTED]
Subject: Long elevation profile
I am trying to extract an elevation profile across a large dataset. I am
working with a 1km DEM of the entire US. The profile crosses the entire
country from Washington, DC, over the Appalachians to Pittsburgh, then down
the Ohio River to the Mississippi, then up the Mississippi to the Missouri.
It then goes up the Missouri River to it's source, over the Rocky Mountains,
and eventually down the Columbia River to the Pacific Ocean. Sound familiar?
It should - it is the path of the Corps of Discovery, lead by Meriwether
Lewis and William Clark to explore an all water route to the Pacific Ocean,
while exploring the newly acquired Louisiana Territory.
The reason I explained all that is, since the route is not one or two line
segments, but a rather detailed path with LOTS - and I mean 1000s - of
vertices.
I obviously can't use ER Mapper's "transect" tool. Does anyone have any
strategies they have used or can suggest that would allow me to construct an
elevation profile of this path? I tried converting my vector layer (of the
path) to raster, but then I don't know how to arrange the cells to construct
the profile.
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Christopher Ferro
GIS/Remote Sensing Specialist
Center for Educational Technologies
Wheeling Jesuit University
Wheeling, WV 26003
Phone: 304-243-4326
Fax: 304-243-2497
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Ezekiel 18:20
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