Volumes in n4ce – AppsinCadd

Links to Volume Types

Video

Prismoidal Volumes

This is the preferred way of calculating volumes, using triangular prisms.
The convention is that Heights Above a Reference Surface are +ve (Material/Cut) and those Below are –ve (Void/Fill). This may appear obvious when written down like this but it may cause problems when working with real models.

If the final design surface is the current model with groups (on-screen) and the reference is the OGL, then you must Swap Cut and Fill to get the correct quantities and sign convention.

The Reporting group in the prism volumes dialog controls what sort of report is displayed for prism volumes. The text in the report can be printed, filed away or copied and pasted into another application. There are three settings.

In n4ce 4.30 and above there is a new option which allows users to calculate volumes using the group depths but only displaying the basic results.

None

No report window is generated.

Summary

The report that is generated only contains information about the active groups and the totals of these groups.

Detailed

The report that is generated contains information about all the groups and also the unassigned triangles. It also contains various totals.

After the prism volumes have been calculated, a table displaying them can be created and placed in the dedicated CAD backcloth. The Plot Table check button allows you to do this and if it is ticked, the dialog to the right will be displayed. This allows you to control which columns are displayed in the table and also which total volumes are displayed.

The Display group allows you to specify the columns that are to be included in the table.

The Balance Volumes check button allows you to display the overall balance volumes in the model. This is simply the difference between the cut and fill volumes. If this volume is positive, it means that there is a surplus of material which will need to be removed from the site to achieve the levels in the design. If it is negative, it means that material needs to be brought in to achieve the levels of the design surface.

The Areas check button allows you to specify the display of areas in the table. Cut and fill areas will be displayed. If this button is checked, the Null Areas check button is also enabled. Null areas are where the projection finds no difference in height between the design DTM and the second DTM. This usually occurs when comparing two surfaces where one surface is made by incorporating data into a copy of the second surface.

Prism Volumes using DTM Groups

The Volumes Group option allows you to take the triangles of a group from the current DTM and project them down through a number of other surfaces. This will produce the volumes between each surface as well as a cumulative volume as you progress down. It is important that you know the order in which the surfaces are to be selected. The data for the various surfaces may have come from borehole information. An example of part of the data tree where borehole information has been imported is shown to the right.

When the option is selected, you will be asked to select and order the DTMs through which the calculations are to take place. This is carried out using the associate models dialog box which was described earlier in this chapter. The list to the left of this dialog shows those DTMs that are available and have not been selected. The list to the right shows those DTMs that have been selected in the order in which processing will take place. Use the arrow buttons to select and deselect DTMs and the Up and Down buttons to change the order of the selected DTMs. You should note that when you import borehole data and create the DTMs for the various strata, these DTMs are automatically associated with the ground-level model.

Once the DTMs have been selected and ordered, you will be asked to indicate the group which you wish to use to control the extent of the calculations. This is carried out using the mouse cursor and you will be asked to indicate any triangle in the required group.

Once the group has been indicated, the calculations will be carried out and a dialog box allowing you to plot a table will be displayed. This dialog only has one option and this allows you to specify whether you wish a column containing the average heights between the surfaces to be included in the table. The table of results can then be plotted in the dedicated CAD backcloth. An example table is shown to the right. Once a table has been plotted, you will be asked to indicate other groups for further calculations and tables.

Prism Volumes Using Line Features

The Volumes Strings option allows you to calculate prism volumes for triangles that are contained within one or more line feature strings. This can be used to calculate volumes for individual spoil heaps or stockpiles. It is similar to the string set in the region control option for prism volumes but you can create volumes for more than one feature string.

After you have indicated the feature strings you are interested in, the string volumes dialog box is displayed. This is very similar to the prism volumes dialog box and most of the options perform the same function.

There are a few options that have been removed. Since the feature strings themselves define individual areas, there is no region control option. Also, there are no options to calculate volumes using group depths or double depths. Finally, there is no option for the detailed reporting of results.

There is also a subtle operational difference in the creation of the equations for the mathematical surfaces. With these options, you are not required to indicate a series of points. Instead, the points that are part of the indicated feature strings will be used and an equation will be calculated for each feature.

If you need to choose and second DTM, a dialog will be displayed asking you to do so and then the calculations will be performed. If you have chosen to plot a table, the string volume table dialog box will be displayed asking you to specify whether certain items are to be added to the table.

There are three checkboxes allowing you to add columns to the string volume table. The Balance Volumes check button allows you to add a column containing the balance volumes rather than just the cut and fill quantities. The Plan Areas check button allows you to add a column containing the plan areas enclosed by each of the indicated line features. If this button is checked, the Slope Areas check button also gives you the option of adding a further column containing the slope areas. An example of a string volumes table is shown below.

String Volumes

String volumes are similar in operation to the contour volumes, discussed below, in that it uses a reference string, normally a feature, to collect triangle in the area of interest and are ideal for quickly calculating spoil heap quantities.

In the situation where there’s no available reference surface, an Inclined Plane can be used. The points in the reference string will be used to calculate a best-fit plane to which the triangle will be projected to.

Section Volumes

Section volumes use an enclosed Area and Distance between sections to calculate a volume and at best is an approximation to the “true volume”. Prisms are better! The choice of the closing surface will vary, and reflecting options like Closed Section, Datum and Two DTM Surfaces. The direction of the baseline used for the sectioning is important. Sections can be stored for plotting later just like normal sections.

Contour Volumes

The Volumes Contours option allows you to calculate volumes using contours within a specific area of a DTM. An example of this is when you wish to isolate volumes at different contour levels for a pond whilst ignoring the remainder of the model. You will be asked to indicate a DTM apex which is within the zone of interest and the contours volumes dialog box will be displayed. The Indicated Point text displays the coordinates of the point that you have indicated.

Contour volume calculations can either produce a single result for one contour value or multiple results where a contour interval is specified. This is controlled by the radio buttons in the Calculation group.

The Interval field in the Parameters group will be enabled if you are carrying out multiple contour volumes and its value specifies the interval at which contour volumes will be calculated. The direction of the calculations can also be controlled by the Mode field. This has three possible settings.

Up to Value

Calculations will take place up to the contour value that is specified in the Value field. This is the mode you should use for calculations in a pond.

Between

Calculations will take place between the contour values specified in the Maximum and Minimum fields.

Down to Value

Calculations will take place down to the contour value that is specified in the Value field. This is the mode you should use for calculations of a spoil heap.

The Plot Table check button enables you to plot a table of your results in the dedicated CAD backcloth. If this button is checked, the contour volume table dialog will be displayed after the calculations have been carried out and the results displayed on the screen. There are only two check buttons and these allow you to plot plan and slope areas in the table.

Single Contour Volumes

If the Single radio button in the Calculations group is set, only a single contour volume will be produced. The mode and limits of the calculations are defined in the Parameters group. After you have indicated the DTM apex, the calculations will be carried out and a dialog box will be displayed showing you the results. Three figures are shown for the volume enclosed by the contour, the plan is of the contour and the slope area of the triangles, or parts of triangles, within the contour.

If a table is required, the contour volume table dialog will be displayed and you will then be given the option to plot the table. An example of a single contour volume table is shown to the right.

For single contour volumes, you are also given the option to create a cross-hatch which graphically highlights the area over which the calculations have taken place. The parameters for the cross-hatch are shown in the Hatching group of the contour volumes dialog and will be created if the Enabled check button is ticked. After the results have been displayed and a table has been plotted, you will be asked to indicate the origin of the hatch pattern and it will be created in the dedicated CAD backcloth.

After the end of this process, you will be asked to indicate another DTM apex for further contour volume calculations.

Multiple Contour Volumes

If the Multiple radio button in the Calculations group is set, multiple contour volumes will be produced. The mode and limits of the calculations are defined in the Parameters group. It is up to you to ensure that as you enter the values in the maximum and minimum fields, they are a multiple of the contour interval.

After you have indicated the DTM apex, the calculations will be carried out and a dialog box will be displayed showing you the results.

The dialog box is tabular and displays each contour value together with the plan area of each contour, the volume enclosed by each contour and the slope area of the triangles, or parts of triangles, within the contour. Two further columns of data are displayed. The dvolume column displays the change in volume between two contour intervals and is the volume of a horizontal slice. The dSl Area column shows the change in slope area between two contour intervals.

The Report button allows you to generate a report window of the results. The report window contains the same information as the multiple contour volume results from dialog above.

If a table is required, the contour volume table dialog will be displayed and you will then be given the option to plot the table. An example of a multiple contour volume table is shown to the right. Note that there is a check button in the multiple contour results dialog which also allows you to specify that you wish to plot a table.

After the end of this process, you will be asked to indicate another DTM apex for further contour volume calculations.

Volumes Using Cross Sections

The Volumes Sections option allows you to define a series of cross-sections and use the areas of the profiles of these sections to calculate volumes. These calculations are normally used as a backup to prove or check the results of the more usual prism volume method. As the spacing between the defined section lines gets smaller, the section volume results will get closer to those results produced by the prism volume method. When the option is selected, the dialog box to the right will be displayed.

Defining the Section Cut Lines

The Definition group allows you to define how the section cut lines are calculated. The Direction field allows you to specify the direction of the cut lines and there are six options.

Sketched Base Line

A sketched baseline is a single segment line of two locations. You are asked to indicate the start and end locations of this line. When section cut lines are generated, they will be perpendicular to the indicated line starting at the first location.

Points Base Line

A points baseline is a single segment line which starts and finishes on two points within the current model. You will be asked to indicate the start and finish points. Again, when section cut lines are generated they will be perpendicular to the indicated line starting at the first point.

West-East

Section cut lines are generated going from west to east. This option is the same as having south to north baseline with the first cut line will be the most southerly

East-West

Section cut lines are generated going from east to west. This option is the same as having a north to south baseline with the first cut line will be the most northerly.

South-North

Section cut lines are generated going from south to north. This option is the same as having an east to west baseline with the first cut line will be the most easterly.

North-South

Section cut lines are generated going from north to south. This option is the same as having a west to east baseline with the first cut line will be the most westerly.

The Position field allows you to define the frequency of the cut lines in the direction of the baseline and there are five options. The first three are used in conjunction with the setting in the Direction field. For each of these three options, the extent of the DTM triangles in the direction of the baseline is calculated to ensure that the section cut lines cover the whole model.

Number

The Number field will be enabled and you should enter the number of spacings between sections that you require here. There will, therefore, be one more section than the value in the field. The spacing of the sections will be calculated from the number and the model extents.

Spacing

The Spacing field will be enabled and you should enter the required spacing of sections. The number of sections will be calculated from the spacing and the model extents. Since n4ce ensures that there is a cut line at the beginning and end of the section baseline, the spacing between the last two sections will not be the same as that defined in the field.

Indicated

You will be asked to indicate the positions of the sections to be calculated. These positions can be indicated in any order as the section cut lines will be sorted after you have finished indicating them but before the calculations take place. The variable spacing between each of the cut lines is calculated and used for the results. Note that two cut lines will be automatically created at the start and endpoints of the extents in the direction of the baseline.

The fourth option in the Position field is called Coord Pairs. If this option is set, you will be asked to select a co-ordinate block which contains pairs of coordinates that define the start and endpoints of the cut lines that you wish to calculate. For the volume results, the distance used is calculated between the mid-points of successive cut lines. Also, the points from the co-ordinate block are assumed to define the order of the cut lines. This option can be useful when carrying out monthly comparisons where using the same cut lines removes possibilities for errors.

The fifth and final option in the position field is called Design String. If this option is set, you will be asked to indicate a design string as the centre line for your calculations. A design string is one where each point has chainage and bearing dimensions. The coordinates of each point on the design string and its bearing dimension define the direction of the cut line at each point. After you have indicated the design string, you will be asked to define extents of the calculations using the dialog box shown to the right.

The Chainages group allows you to specify the range of chainages along the design string in which you are interested. The Start and Finish fields are drop lists which contain the chainages of all the points on the indicated design string. The default values for these are the chainages on the first and last points respectively.

The Offsets group allows you to define the corridor over which calculations should take place. The values in these fields should normally be set to ensure that the whole model is considered. It is possible to set the offsets from the design to the left and right to be different.

Defining the Section Volume Profiles

The Calculations field in the section volume dialog box allows you to define the way in which areas are calculated from the section profiles. There are three options.

Closed Ends

Areas are calculated by projecting each segment of the section profile onto a straight line that joins the first and last point on the section profile.

Datum Height

Areas are calculated by projecting each segment of the section profile onto a datum level. This method assumes that there are vertical drops or rises at either end of the section profile. If this option is set, the Datum Height field in the section volume dialog box is enabled and you should enter the required datum here.

Second Surface

Areas are calculated by projecting each segment of the section profile onto another section profile which is calculated from a second DTM. If this option is set, you will be asked to select the second DTM surface from which the other section profile is to be calculated.

The examples above show the polygons that may be created for a section profile area calculation. Note that it is possible to produce cut and fill results as shown in the datum height example. As regards cut and fill values, the same convention applies to section volumes as it does to prism volumes. Where the current DTM is above the second surface, this is considered to be cut. If you are working from a design surface, the Swap Cut & Fill option in the section volume dialog allows you to arrange the results in the correct order.

Whichever method you use to calculate the area of each section profile, the Group Depths check button allows you to take into account any group depths that are associated with any of the triangles that have been used in the calculation of the section profile. If you are calculating areas using a second DTM surface, a Double Depths check button will appear and you can then also take into account any group depths in the second DTM surface.

Reporting Section Volume Results

The remaining check buttons in the section volume dialog box control how you wish the results to be reported or plotted.

The View Sections check button allows you to specify whether the calculated cross-sections are to be displayed in a section viewing window or not. This is useful if you either wish to carry out a visual check to ensure the sections are correct or you wish to save the sections for later plotting.

The Generate Report check button allows you to specify whether a report window containing the results is displayed or not. An example of the section volume results window is shown to the right. You can print these results, save them to a file or copy the text into another application for report purposes.

The Plot Table check button allows you to plot a table of the results in the current model's dedicated CAD backcloth. If checked, the section volume table dialog box will be displayed allowing you to specify which items are to be displayed in the table. The Element Volumes check button controls the display of the individual volumes between the cross-sections. The Section Areas check button controls the display of the areas of each of the cross-sections.

The Naming group specifies how each of the lines of results in the table is labelled and there are three options.

Name

The numeric numbers of each cross-section area displayed.

Chainage

The chainages of the cross-sections along the baseline are displayed.

Both

The numbers and the chainages of the cross-sections along the baseline are both displayed.

Volumes Using Datums

At first, it would appear that there is little difference between contour volumes and datum volumes. There are, however, two major differences. The datum volumes calculate quantities at each datum value that are both

above and below the datum whereas contour volumes calculate only one of these. Also, the datum volume calculations are carried out over the whole of the current DTM rather than the triangles, or parts of triangles, contained within a contour.

To give an example of the terms above and below, take a concrete water tank of a known area which can contain water up to a known level. There is, however, sediment in the bottom of the tank which is not at a constant level. This sediment has been surveyed and a DTM of it produced. The customer would like to know what volume of water is in the tank at any given level and also the volume of sediment that is above that level. Therefore, each “above” volume in the results is the volume of sediment above each datum whilst each “below” volume is the volume of water below each datum.

The Volumes Datum option allows you to calculate volumes over a series of datum values. When selected, a dialog box similar to that shown on the right will be displayed.

The Calculations group define the range over which the datum volumes are to be calculated. The Interval field in the Datums group defines the interval used to calculate volumes. Using this value, the maximum and minimum datums within the DTM triangles can be calculated. The maximum datum would be the maximum height in the DTM triangles rounded up to the next datum using the interval. The minimum datum would be the minimum height in the DTM triangles rounded down to the next datum using the interval.

There are four datum range options.

All

Volumes will be calculated across the full height range of the DTM triangles using the minimum and maximum datums from the DTM triangles.

Between

Volumes will be calculated between a maximum and a minimum datum. These are defined in the fields in the Datums group.

Above

Volumes will be calculated from the maximum datum for the DTM triangles down to a datum value specified in the Minimum field.

Below

Volumes will be calculated from the minimum datum for the DTM triangles up to a datum value specified in the Maximum field.

When entering the maximum and minimum datums into the appropriate fields in the dialog, it is up to you to ensure that they are a multiple of the datum interval.

The datum volumes are then calculated and displayed in a report dialog. This displays each datum together with the prism volume results of the DTM when compared to each datum. It also gives the change in volume between each of the calculated datums.

The Report button allows you to generate a text report window which can be printed, saved or copied to another application. The report window contains the same information as the datum volume results from the dialog.

The Plot Table check button allows you to plot a table of the results in the dedicated CAD backcloth. If you plot a table, the datum volumes table dialog will be displayed. There are only two check buttons in this dialog and they control the display of the volume deltas and the areas. An example is shown below.