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Digitizing contours and adding Z-values

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#16
Martin Gamache

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The problem really is very easy to solve in almost any language. As long as you have access to the file format, you wouldn?t even need any GIS software.

You only need to know:

- which contour lines
- their equidistance
- starting height



I would think you would also need to know which way is up or down. So a starting and ending height no?

#17
Kartograph

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Well, of course. That?s implied by "which contour lines". That?s what I meant with heeding the IDs. Actually I frist put a rather longuish pseudocode example in my post which handled that and some other stuff. But I thought that was starting to get confusing.

Depending on the software used for digitizing, it?d be a breeze to even implement a small set of buttons for this input, with, say, VB.

I?d really love to give it a shot. So if anybody wants that functionality for a specific program and a specific filetype, I?d love to tinker around with the idea.

The interesting part would be to implement the graphical selection. But with ArcGis this is a given and should really be possible with a little work.

Don?t know much about manifold, though.

#18
benbakelaar

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I don't understand why ArcGIS Spatial Analyst -> Contour tool doesn't do this. It asks for a base contour, the contour interval, and a z-index multiplier. Yet it doesn't work? At least not on this image (I've taken out the text on the copy I imported).

Attached File  contour_map.gif   45.15KB   116 downloads

#19
Kartograph

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Well, but Vanilla spatial analyst does this for the whole area, doesn?t it? Or can you select parts of it? But surely you can script that.

Still ArcGis is way too expensive to have around for small endeavours. I say it?s even possible without any dedicated GIS.

#20
benbakelaar

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Like I said, I'm not even at the level of a contour amateur, so I can't figure out how this program works.

BLACKART - www.terrainmap.com

From the help file:
BLACKART is not a generalized raster-to-vector conversion utility. It does not produce a vector image at all. Since the interpolation input files required by the BLACKART solvers are sparse matrix representations of equations derived from raster elevation grids, no vector image files are needed or produced by this utility.

What BLACKART will do is convert graphic image files of unencoded elevation contours (or other non-graphical representations of such contours) into raster encoded elevation files by use of contour line tagging and other custom algorithms designed expressly for this purpose. It will
then interpolate the encoded contour line files into raster elevation grids (by computing the elevations between the contours) using the Franklin algorithm. This produces a terrain representation free from the unwanted artifacts common to many other interpolation algorithms.


Hope that helps some of you!

#21
Hans van der Maarel

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Well, it looks like I have the concept together in FME, screenshot and workbench + sample files are attached. Took me roughly 15 minutes to figure this one out.

Attached File  screenshot.jpg   261.62KB   141 downloads

Attached File  assign_contour_elevations.zip   17.97KB   121 downloads

One word of warning though: I did this with a very basic set of contour lines, to prove that it's possible. If you want to scale this up bigtime there might be some problems with 2 of the transformers used here (SpatialFilter and NeighbourFinder) which can take a lot of time to process.
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#22
anatolij

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thanks for your reactions
somebody asked for sample data, here is something (1bit BMP, 2560x2560 meters, 5120x5120px, vertical separation is 5 m). http://mzak.herma.org/cont.zip

I've made small application and maxscript and I'm digitizing 10x10km area in about 30 minutes now, which is huge progress since the first tries with vextractor. I'm still debugging, so it's gonna be even a bit faster maybe.
http://mzak.webzdarma.cz - jet engines, airshows, FS sceneries, Lock On tutorial, 3D Mark results




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