Its not a glitch in Mathcad.
The main problem is that you are not provide a surface and IMHO Mathcad should even refuse to do a surface or contourplot of that data.
You provide a simple list of points in 3D space. So all you could ask Mathcad for is to plot those points and maybe connect them in the order defined by your vector - this is done using a scatter plot.
You may create your own interpolation routine to get a surface, but as it looks to me some of your points are lying one on top of the other (at least close). So an interpolation routine, providing for any given pair of z and x value a height y, would be ambiguous.
BTW, Is there any deeper reason for naming abscissa, ordinate and aplicate z,x,y rather than x,y,z as usual?
Facit: The surface you see when you plot your data points is not the surface you want to be plotted. Its Mathcad's interpretation of your data and its a surface which comes close to your points and is also defined outside the region given by your points. I am not sure how exactly Mathcad interpretes your data, but by looking at the last plot in the attached sheet and turning around the plot you see that not all points are lying in the surface created by Mathcad. I embdedded the data of your excel sheet so the file is selfcontained which is more convenient here.
Its unusual that you create your data in Excel and try to use Mathcad for plotting (I know, missing 3D capability). Usually people are going the opposite way and calculate their data in Mathcad. How is the data you use derived? Any chance of being able to provide the three matrices which Mathcad needs to plot a surface? Or at least - can you privide a table with heights (y-values) for every gridpoint in a rectangular(!) z,x-area?
