Introduction to Contouring


Contouring Topics


ChemPoint Professional provides powerful contouring capabilities for parameter concentrations. Contouring features include:

  • Highly customizable contour plots
  • Contour over a background image such as an aerial photograph of the facility
  • Three different gridding models (inverse distance, kriging, and triangulation)
  • Save and load custom contour diagrams as template files


Contouring in ChemPoint is faster and more convenient that exporting to third party contouring packages.

  • No need to switch programs
  • Easily switch parameters and dates
  • Unit conversion is handled within ChemPoint


Introduction to the Contouring Process

  1. Determine the X, Y, and Z values to be contoured. In ChemPoint, the X and Y values are the Easting and Northing values for sampling locations. The Z value is some parameter concentration for a specified sampling date.
  2. Create a grid of Z values. This is the complicated part of contouring. You specify a grid size (such as 50 by 50). You also specify a gridding method such as kriging, inverse distance, or triangulation. The gridding method determines how the Z value for each node in the grid is calculated from the Z value in step 1.
  3. From the grid of Z values in step 2, create and display contour isolines.


Within these three steps, there are many options from which you must choose:

  • What gridding method to use and what specific options for the method are appropriate?
  • How many isolines do you want and what is the Z value difference from one line to the next?
  • What colors, line styles, and fonts do you want to use to create the contours?


Important Warnings About Contouring


  1. Contouring involves many calculations and requires a lot of memory, so it can be very slow. A fast computer with a lot of available memory is best for extensive use of contouring.
  2. Contouring algorithms are mathematically complex. Different gridding methods can provide significantly different results. Many environmental scientists are skeptical about relying extensively on computer generated contour diagrams. Be sure you understand that a contour diagram provides only one possible representation of the data, but not necessarily the correct one.