Excel Chart Contours should be smooth as done in surveying


G

Guest

Excel Chart Contours should be smooth as done in surveying.
The countours plotted are very coarse and with lot of kinks.
In actual survery contour plotting based on levels at regular grids,
contours are plotted smoothly and represent physical features of ground.

Excel has to use some kind of interpolating algorithm and draw the contours.

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http://www.microsoft.com/office/com...d321c068c4&dg=microsoft.public.excel.charting
 
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J

Jon Peltier

One alternative, since the charting algorithms aren't going to improve any
time soon, is to do your own interpolation of the data. It won't make the
data any smoother, but the chart will at least perform the straight
interpolation in a nicer manner. For example, you could insert rows and
columns in the original data, and use simple formulas to interpolate the
in-between values. More complicated formulas could be used to achieve better
smoothing.

The problem is that the only way to improve resolution in the chart is to
insert more rows and column (and calculated values) into the data. The chart
will not make curved boundaries between the colored regions. When the
resolution is increased beyond a certain point, there are too many lines and
not enough colored surfaces; when you format away the lines, you lose all
lines: not just the vertical and horizontal gridlines, but also the lines
between colors.

Surface and contour charts in Excel need a lot of work. Hopefully before
Excel 2010 (or whenever the next version comes out) they will have made some
real, non-cosmetic improvements to the charting capabilities.

- Jon
 
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G

Guest

Unless contours in surveying are done with something like tracing elevations
with stereo pairs of aerial photos, they're formed by interpolating between
known points of X&Y position and height. See "digital terrain model" or
"digial ground model" ("DGM") for more information. Interpolation is usually
done forming triangles between known points and solving the equations of the
local triangular planes for the "missing" points; see "triangulated
integrated network," or "TIN." Then smoothing functions are used to connect
the points to make smooth lines; see "splines" or "b-splines" or, if you want
the really cool version, NURBS, which stands for "Non Uniform Rational Bézier
Spline."

Point is, drawing pretty-looking smooth contours is a lot of work! I'd
rather see Excel do other things than be a contour mapping package. With all
due respect, get AutoCAD if you want that.
 

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