<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<div class="moz-cite-prefix">Nav,<br>
<br>
I don't know about the gdal routines specifically, but:<br>
<ol>
<li>Re. dem/dtm generally, the most significant factor in
interpolation results is the quantity (density, really) and
quality of the source data, not the interpolation algorithm.</li>
<li>Re. contours generally, they are cartographic artifacts, not
geographic features and will never be more accurate than the
source data (unless you know the data are very "noisy" and
ought to be smoothed.</li>
<li>Re. segments vs splines, it depends whether the segment
end-points are fixed and only their interiors are shifted, or
the corners are shifted to make them rounded and the interiors
fixed. The former is much better since the end-points are
"primary" interpolations (based on data) and the interiors
"secondary" (based on primary). Smoothing out the contours
(either way) will make them cartographically pleasing, but the
degree of "curviness" should depend on the assumed ruggedness
of the original terrain (more rugged => less smoothing).</li>
</ol>
Hoping that helps and that others will comment on the specific
gdal routines,<br>
<pre class="moz-signature" cols="72">Martin Feuchtwanger <a class="moz-txt-link-abbreviated" href="mailto:feumar@shaw.ca">feumar@shaw.ca</a> 604-254-0361
<a class="moz-txt-link-freetext" href="http://members.shaw.ca/geomatics.developer">http://members.shaw.ca/geomatics.developer</a>
</pre>
On 13/02/2013 7:15 PM, nav wrote:<br>
</div>
<blockquote cite="mid:1360811719382-5034148.post@n6.nabble.com"
type="cite">
<pre wrap="">Am creating an app which correctly calculates contours from a DEM file or any
height-map given to it. The correctness of the contour holding the most
importance, since a person viewing the contours shouldn't end up taking
wrong planning decisions and maybe losing their life by the route they
choose after looking at the map.
I have already tried using GDAL 1.7 source code, compiled it and added some
features of my own to it for some other objective. Now I want to
add-to/modify the source to be able to use the contour generation function
of GDAL in C++.
But before proceeding, I wanted to know:
1. If GDAL offers the best free contour generation algorithm available or is
there any other library which I can link to my code and feed my DEM map to
it and receive contour vector lines (or go thru research papers and
implement the contour generation algorithm myself in C++)? If GDAL, then why
is it the best?
2. A generated contour will basically be points connected with straight
lines. Is it more correct for a contour to be depicted with connected
straight lines or will it give a more correct result to use a spline to
smoothen out the lines?
I won't be interpolating any contours or the DEM because I've read on this
website that interpolation leads to incorrect results.
--
View this message in context: <a class="moz-txt-link-freetext" href="http://osgeo-org.1560.n6.nabble.com/Most-optimal-algorithm-for-contour-correctness-tp5034148.html">http://osgeo-org.1560.n6.nabble.com/Most-optimal-algorithm-for-contour-correctness-tp5034148.html</a>
Sent from the GDAL - Dev mailing list archive at Nabble.com.
_______________________________________________
gdal-dev mailing list
<a class="moz-txt-link-abbreviated" href="mailto:gdal-dev@lists.osgeo.org">gdal-dev@lists.osgeo.org</a>
<a class="moz-txt-link-freetext" href="http://lists.osgeo.org/mailman/listinfo/gdal-dev">http://lists.osgeo.org/mailman/listinfo/gdal-dev</a>
</pre>
</blockquote>
<br>
</body>
</html>