Volumes in n4ce Professional
If you had to calculate volumes by hand then your options are limited. You may choose to calculate the plan height and multiply it by the average area, or use a more traditional section end area method. However, with the advent of the computer, much quicker and more accurate techniques are possible.
The key to calculating accurate volumes is a digital terrain model (DTM). Whilst there are a number of different types, the most popular involve triangular facets. In the Lite edition, we introduced volume calculations using prisms. These are toblerone or triangular columns from a DTM surface to a reference, which could be a Datum, best fit Numeric Surface or another DTM. When comparing two DTM's an intermediate height difference surface called an Isopachyte will be calculated. This takes care of problems like matching break lines and boundaries in both DTM's.
A number of additional options are provided with the Professional edition, including volumes from Sections, Strings and Contours. We will also see how Groups can influence volume calculations, especially where depths of construction are involved. Results are presented in Reports and Tables.
A very useful feature is introduced into Professional called Group Depths. Groups are used to isolating areas of your model/survey to identify different surface types like footpaths, grassed areas or different spoil heaps.
Groups can also be used in calculating areas, volumes and to control plotting of contours. The section shown below identifies group depths, which can be used in volume calculations to remove construction depths to expose formation levels.
Whilst prism volumes are considerably more accurate than sections, many users also like to provide the end use with sections calculated during section volumes. This provides a comfort factor and a visual representation that the right surfaces are being used.
|
When using Volumes by Sections, you will be presented with various options including a reference baseline Direction, Positioning of sections and how each section will be closed for Calculations. An example of section volumes is shown above. A special option allows you to extract sections using previously stored XY pairs of coordinates. |
|
|
|
The String volumes option has been designed to allow you to select individual sets of triangles. Group depths are not used here.
The triangles used in volume calculations are encircled with a feature string and have been specifically designed to present volumes from individual spoil heaps or hollows. |
Finally, the last option included here for volume calculations is called by Contour and calculates volumes contained within a contour band. A starting point is required, which could be a high point or a low point depending upon whether you are working on a hill or valley.
Fanning out from the high or low point, contours surrounding this point are searched for until a nominated final contour value is found. Prism calculations are used to find volumes within the final banded contour, with values being presented in a table as shown above. You are also given the option to plot a hatch pattern for the area selected. |
