Dtm Surfaces

DTM Surfaces in SURPAC 6.0

May 2007

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Copyright © 2007 Surpac Minex Group Pty Ltd (A Gemcom Company). All rights reserved.

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While every precaution has been taken in the preparation of this manual, we assume no responsibility for errors or omissions. Neither is any liability assumed for damage resulting from the use of the information contained herein.

All brand and product names are trademarks or registered trademarks of their respective companies.

Contributors

Rowdy Bristol Kiran Kumar Phil Jackson

Surpac Minex Group Perth, Western Australia

Product

Surpac 6.0

Document Release Date

May 2007

Table of Contents Overview...................................................................................................................................... 4

Surface Modelling Concepts ..................................................................................................... 5 Naming Conventions ................................................................................................................................6 Breaklines and Spot Heights ....................................................................................................................7 Graphical vs File-based options ...............................................................................................................8

Setting the Work Directory ........................................................................................................ 9 Task: Setting the Work Directory...........................................................................................................9

Creating a DTM ......................................................................................................................... 10 Task: Perform Graphical Creation of a DTM .......................................................................................10 Task: Perform File-based DTM creation..............................................................................................12 Task: Create a DTM from Spot Height Data........................................................................................14 Task: Create a DTM Using Breaklines and Spot Heights ...................................................................17

Viewing DTMs ........................................................................................................................... 19 Task: Colour a DTM by Elevation........................................................................................................19 Task: Performing Graphical Animation................................................................................................20 Task: Saving Images of a Graphical Animation...................................................................................24

DTM Volume Calculations ....................................................................................................... 26 Create a Volume Boundary String..........................................................................................................26

Task: Create a Boundary String Using the File-based Method ...........................................................26 Task: Create a Boundary String Using the Graphics-based Method ..................................................28

Calculate The Volume Between Two DTMs...........................................................................................29 Task: Calculate Cut and Fill Volumes..................................................................................................29 Task: Net Volume Between DTMs ......................................................................................................31

Clipping a DTM ......................................................................................................................... 36 Task: Clipping a DTM - File Based Method.........................................................................................36 Task: Clipping a DTM - Graphics Based Method ................................................................................38

Sectioning a DTM ..................................................................................................................... 41 Task: Create a DTM section axis line..................................................................................................41 Task: Create DTM sections .................................................................................................................42 Task: Create DTM Contours – Graphics Based..................................................................................44 Task: Create DTM Contours – File Based...........................................................................................45 Task: Create Index Contour file with Annotations ...............................................................................47

Draping a String Over a DTM...................................................................................................50 Task: Draping a Spot Height String over a DTM .................................................................................50 Task: Draping a Non-Spot Height String over a DTM .........................................................................51

Image Draping........................................................................................................................... 54 Task: Drape an image over a DTM. ....................................................................................................54

DTM / DTM Intersections.......................................................................................................... 57 Task: Create an Upper Triangles Surface of 2 DTMs .........................................................................57 Task: Create a Lower Triangles Surface of 2 DTMs ...........................................................................58 Task: Create Solid by Intersecting 2 DTMs.........................................................................................59

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Overview Surface Modelling uses triangulation to create two-dimensional models known as Digital Terrain Models (DTMs). This document introduces the theory behind surface modelling processes and provides detailed examples using the surface modelling functions in Surpac. By working through this manual you will gain skills in the construction, use of and modification of DTMs.

Requirements

This tutorial assumes that you have a basic knowledge of Surpac. If you are a new Surpac user, you should go through the Introduction to Surpac manual before going through this manual.

You will also need:

• To have Surpac installed on your computer. • The data set accompanying this tutorial.

Objectives

The objective of this tutorial is to allow you to work with some surface modelling tools. It is not intended to be exhaustive in scope, but will show the workflows needed to achieve results. You can then refine and add to these workflows to meet your specific requirements.

Workflow

Start

Create DTM

ContouringCreate SectionsCalculate Volumes

Image and String Drapes

DTM/DTM Intersections

String File

Surface Modelling Concepts Naming Conventions

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Surface Modelling Concepts Digital terrain models (DTMs) are created from strings.

Triangles are created between points on the strings.

The result is a set of non-overlapping triangles.

Surfaces are used in Surpac for such things as 3D visualization and for calculating volumes. Almost any surface can be modelled as a DTM, including natural topography, lithological contacts, bedrock/overburden contact, or water tables.

DTMs are made of triangles, with each point of each triangle matched to a point in the original string file. Consequently DTM files are not valid without the original string files. That is, a DTM file cannot be opened if the original string file of the same name is not accessible.

DTMs cannot fold back on themselves. That is, a DTM cannot have multiple Z values for a given X, Y coordinate. It is not possible to model overhanging or vertical surfaces with a DTM surface.

Surface Modelling Concepts Naming Conventions

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Naming Conventions The objects you create in Surpac are numbered by a system similar to that of string and string segment numbers.

String object

Segment trisolation

Point triangle

When you define an object you explicitly assign it both an object number and a trisolation number. The object is then always referred to by this object and trisolation number.

The object number may be any in the range of 1 to 32000. The trisolation number may be any positive integer. However, for most functions the object must be named object 1, trisolation 1.

Surface Modelling Concepts Breaklines and Spot Heights

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Breaklines and Spot Heights Breakline strings are those which represent linear physical features that you can see in the real world e.g. crest of a pit, a fault in a geological model, a contour in a pit.

Spot height strings contain points which represent non-linear or point features, such as hill peaks, surface low points, gridded points, borehole collars etc. The lines connecting the points in the spot height string in graphics do not infer a physical line.

Surface Modelling Concepts Graphical vs File-based options

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Graphical vs File-based options A DTM can be created in two ways to best suit the data you wish to model.

Graphical DTM operations allow you to view your results immediately. However, for large data files, the processing time may be prohibitive. The file-based tools allow you to perform DTM operations directly on the file data, saving both memory usage and creation time.

For example, to create a DTM graphically, you would use:

To create a DTM using a file-based option, you would use:

Setting the Work Directory Graphical vs File-based options

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Setting the Work Directory A work directory is the default directory for saving Surpac files. Files used in this tutorial are stored in the folder:

<installation directory>\demo_data\tutorials\dtm_surfaces

where <installation directory> is the directory in which Surpac was installed.

Task: Setting the Work Directory 1. In the Surpac Navigator, right-click the dtm_surfaces folder. 2. Select Set as work directory.

The name of the work directory is displayed in the title bar of the Surpac window.

Creating a DTM Graphical vs File-based options

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Creating a DTM It is important to understand how a string file relates to a DTM. Once a DTM has been created, any modifications to the string file will make the existing DTM invalid.

Task: Perform Graphical Creation of a DTM

1. Click the Reset graphics icon . 2. Open topo1.str.

3. Choose Surfaces > Create DTM from layer. 4. Enter the information as shown, and then click Apply to create the DTM surface.


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The DTM is displayed.

5. Choose File > Save > String/DTM. 6. Enter the information as shown, and then click Apply.

Note: Because the string file already exists, you will be asked if you wish to replace it.

7. Click Yes.

If you want to see all of the steps performed in this task, run

01a_create_DTM_from_layer.tcl

Note: You will need to click Apply on any forms presented.


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Task: Perform File-based DTM creation You will now create a DTM from the string file pit1.str using file-based DTM creation. You will use this function to demonstrate the impact of using strings as breaklines.

1. Click the Reset graphics icon . 2. Choose Surfaces > DTM File functions > Create DTM from string file. 3. Enter the information as shown, and then click Apply.

Note: In this case the Strings to act as break lines checkbox is not ticked

The message window informs you of the processing as the DTM is created. When processing is finished, you will see a log file, which is a report containing information about your DTM.


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4. Close the log file. 5. Open pit1.dtm.

Notice that there are triangles in the DTM that are created across strings. This is not a desired result.

6. Choose Surfaces > DTM File functions > Create DTM from string file. 7. Enter the information as shown, and then click Apply.

Note: In this case, the Strings to act as break lines checkbox is ticked.

8. Close the log file.


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9. Open pit1.dtm.


_01b_create_DTM_from_string_file.tcl


Task: Create a DTM from Spot Height Data

1. Click the Reset graphics icon . 2. Open dhc2.str.

Note: This file is a survey of drill hole collars prior to mining and may be used to model the natural surface.

Notice that the file consists of one spot height string. 3. Choose Display > Hide everything. 4. Choose Display > Point > Markers.


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5. Enter the information as shown, and then click Apply.

The data is displayed as markers.

6. Choose Surfaces > DTM File functions > Create DTM from string file.


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A log file is created as shown.

8. Close the log file.


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9. Open dhc2.dtm.


_01c_create_dtm_from_spot_height_data.tcl


Task: Create a DTM Using Breaklines and Spot Heights

1. Click the Reset graphics icon . 2. Open pit2.str. 3. Choose Display > Strings > With string numbers, and then Apply the form to display all string

numbers.

Notice that string 9999 is a spot height string. 4. Choose Surfaces > DTM File functions > Create DTM from string file.


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1. Click the Reset graphics icon . 2. Open pit2.dtm.


_01d_create_dtm_using_breaklines_and_spot_heights.tcl


Viewing DTMs Graphical vs File-based options

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Viewing DTMs Overview:

In this chapter you will learn two ways of displaying dtm data. Firstly you will colour a DTM of a pit by elevation. Then you will set up a flythrough movie.

Task: Colour a DTM by Elevation

1. Click the Reset graphics icon . 2. Open pit1.dtm.

3. Choose Display > Surface or solid with colour banding. 4. Enter the information as shown, and then click Apply.


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The result will look like the image shown.


_02_colour_dtm_by_elevation.tcl


Task: Performing Graphical Animation

You will now digitise a string to follow and use the View along string function to fly in the direction of the string.

1. Click the Reset graphics icon . 2. Open eom_pit.dtm.

3. Choose Display > Surface or solid with colour banding.


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5. Choose View > Data view options > View scale factors. Tip: To give a more realistic view, increase the z scale by a factor of 3. 6. Enter the information as shown, and then click Apply.

7. On the status bar at the bottom of the screen, click the design string button . 8. Set the Design String Number to 500, and then click Apply.

Next you will create a new layer for the design string.

9. Click the New button in the Layers Pane.


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10. Enter fly as the name of the new layer, and then click Apply.

11. From the toolbar, select the snapping list options and click on the Triangle option.

12. On the toolbar, select the icon to activate the function Digitise a point at cursor location. 13. Digitise a string similar to that shown.

14. Press the ESC key to terminate the function. 15. Choose Edit > String > Smooth. 16. Enter the information as shown, and then click Apply.


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17. Save this string as fly1.str.

18. Right click on the eom_pit.dtm layer in the Layers pane to bring up a popup menu. 19. From the popup menu, click Selectable to turn it off for the layer.

Notice that the padlock becomes closed, indicating that the layer is no longer selectable.

This ensures that when you start the animation, the string will be selected and not the DTM.

20. Choose View > Data view options > View along a string.


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22. Click any point on string 500 to start the animation.


_03a_fly_through.tcl


Task: Saving Images of a Graphical Animation 1. Click the Zoom All icon . 2. Choose View > Data view options > View along string. 3. Enter the information as shown, and then click Apply.


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Note: This process will produce many output files so the Max frame distance has been changed to capture an image every 20 metres.

4. Click any point on string 500 to start the animation. Note: The output files (fly001.gif, fly002.gif…) can be used to create an animated gif file using other software


_03b_fly_through_save_images.tcl


DTM Volume Calculations Create a Volume Boundary String

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DTM Volume Calculations Overview:

In this chapter, you will learn how to:

• Create a volume boundary string.

• Calculate the volume between two DTMs.

A critical step in the calculation of volumes is to create or identify a volume boundary string. The boundary string limits the volume to the two dimensional area enclosed by the boundary string. The boundary string must be a closed string.

You will use the boundary string in either of the two methods available for calculating volumes. DTM Cut and Fill Volumes will report both positive (fill) as well as negative (cut) volumes separately. This is the recommended method of calculating DTM volumes. Net DTM Volumes is useful for automatically saving the volume calculated, slope areas of DTMs, and other values in an output string file. The volume reported in Net DTM Volumes is the addition of both positive (fill) volumes and negative (cut) volumes within the boundary string. If you only want to report cut or fill volumes with this function, it is critical that the boundary string accurately represents the cut or fill area.

Create a Volume Boundary String Task: Create a Boundary String Using the File-based Method In this case, you will display the DTMs only for clarity.

1. Click the Reset graphics icon . 2. Open pit1.dtm and topo1.dtm.

3. Choose Surfaces > DTM File functions > Line of intersection between two DTMs.


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5. Open intersection1.str.

6. Click the icon to toggle the triangle faces off, displaying only the boundary string.


_04a_create_boundary_string_file_based.tcl



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Task: Create a Boundary String Using the Graphics-based Method In this case the DTMs must be displayed in graphics because the function uses graphics layers to determine its input and output.

1. Click the Reset graphics icon . 2. Open topo1.dtm and pit1.dtm. 3. Choose Surfaces > Clip or intersect DTMs > Line of intersection between two DTMs. 4. Enter the information as shown, and then click Apply.

Note: In the graphics-based method, you need to save the string in the intersection layer to a string file if you

wish to use it for further processing

The result is displayed in graphics.


_04b_create_boundary_string_graphics_based.tcl


DTM Volume Calculations Calculate The Volume Between Two DTMs.

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Calculate The Volume Between Two DTMs. Task: Calculate Cut and Fill Volumes

Note: In order to perform this task, the file intersection1.str must exist. If it does not exist, run macro _04a_create_boundary_string_file_based.tcl

1. Click the Reset graphics icon . 2. Choose Surfaces > Volumes > Cut and fill between DTMs. 3. Enter the information as shown, and then click Apply.


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You will see a report like the following:


_05a_cut_and_fill_volumes.tcl



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Task: Net Volume Between DTMs

1. Open pit2.dtm. 2. Choose Display > Strings > With string numbers. 3. Enter the information as shown, and then click Apply to display string 2.

cs

Note: String 2 of pit2.str is used as the boundary string for the volume calculation.

4. Open dhc2.dtm.


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5. Right click to the right of the menus, move the cursor to Toolbars, and then click Scale and transparency.

6. Drag the transparency slider to set the transparency of triangles to 50%.

The DTMs are displayed as shown.

7. Choose Surfaces > Volumes > Net volume between DTMs.


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9. Enter the information as shown. 10. Left click, then right click the check box as shown, and select Field Help.

11. Close Field help. 12. Click Apply.

Next you will be prompted to save the triangles from each DTM clipped by the boundary string.


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Note: It is not necessary to save the modified DTMs.

13. Leave the next two forms blank, and click Apply.

The volume report shown is pit2.not, which is displayed on the screen.


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14. Close pit2.not. 15. Open bdyres2.str. 16. Choose Display > Point > Attributes. 17. Enter the information as shown, and then click Apply.

The result is displayed.


_05b_net_volume_between_dtms.tcl


Clipping a DTM Calculate The Volume Between Two DTMs.

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Clipping a DTM Overview:

DTM triangles can be clipped to prepare a DTM for solids modelling, or simply for viewing a file in graphics. The boundary string may consist of any number of closed segments and may contain clockwise and internal anticlockwise segments, (i.e. representing pillars or waste volumes).

Task: Clipping a DTM - File Based Method

1. Click the Reset graphics icon . 2. Choose Surfaces > DTM File functions > Create DTM from string file. 3. Enter the information as shown below, and then click Apply.

Note: In this case we are using the same string to clip the dtm as was used to define the boundary of the dtm. Since the operation was performed directly on the input files, there is no need to manually save the DTM file.

4. Close the log file. 5. Open back1665.dtm.


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The DTM has been clipped to the borders defined by the back1665.str string file.


_06a_clip_dtm_file_based.tcl



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Task: Clipping a DTM - Graphics Based Method

1. Click the Reset graphics icon . 2. Open lev1665.str.

3. Choose Inquire > Segment properties and select each segment. Notice that the pillars are all anti-clockwise and the drives are all clockwise.

4. Choose Surfaces > Create DTM from layer. 5. Enter the information as shown, and then click Apply.


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6. Choose Surfaces > Clip or intersect DTMs > Clip DTM with string. 7. Select any point on the string. 8. Enter the information as shown, and then click Apply.


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9. Save the file as lev1665.dtm.

This is one way of beginning to create a 3D model of these underground workings. If you want to see all of the steps performed in this task, run _06b_clip_dtm_graphics_based.tcl


Sectioning a DTM Calculate The Volume Between Two DTMs.

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Sectioning a DTM Overview:

This function allows you to create horizontal, vertical or inclined sections through a DTM.

The plane of intersection of the sections is defined by entering the Y, X and Z coordinates at each end of a three dimensional axis line and by specifying the interval along that axis at which sections are to be taken. The first section is taken at the start of the axis and then sections are taken at the specified intervals along the axis until the end of the axis is reached. Sections are taken at prescribed ranges or intervals, and are only created where the section intersects data.

Task: Create a DTM section axis line

1. Click the Reset graphics icon . 2. Open pit1.dtm. 3. Choose Create > Section axis by coordinates. 4. Enter the information as shown, and then click Apply.

The axis line is displayed.

5. Save pit1.dtm. If you want to see all of the steps performed in this task, run _07a_create_section_axis_line.tcl


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Task: Create DTM sections

1. Click the Reset graphics icon . 1. Open pit1.dtm. 2. Choose Display > Section axis line. 3. Choose Surfaces > Create sections from DTM. 4. Enter the information as shown, and then click Apply.


Note: The first section is extracted from the axis start. Sections will not be extracted past the axis end point.


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The data is displayed as shown.

Notice that the axis line is displayed in the left pane. In the right pane are the resulting sections, displayed in section coordinates.


_07b_sectioning_pit.tcl



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Task: Create DTM Contours – Graphics Based

1. Click the Reset graphics icon . 2. Open pit1.dtm. 3. Choose Surfaces > Contouring > Contour DTM in layer. 4. Enter the information as shown, and then click Apply.

The results are as shown:


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5. Change the active layer to slice.

6. Save the data to pitcon5.str.


07c_section_pit_by_elevation.tcl


Task: Create DTM Contours – File Based

1. Click the Reset graphics icon . 2. Choose Surfaces > Contouring > Contour DTM file. 3. Enter the information as shown, and then click Apply.



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6. Open contour1.str.


08a_create_dtm_contours_file_based.tcl



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Task: Create Index Contour file with Annotations

If you intend to use the contours for plotting, you may wish to plot the index contours (or contours at some specific interval) in a different colour to other contours. For example, if contours were extracted at intervals of 2, then index contours would probably be at intervals of 10, that is 10, 20, 30, etc.

These index contours may be saved to an Index contour string file thus making it easy to plot the index contours using a different colour on a hardcopy map.

If you choose to create an index contour file, then the index contours will not be in the contour string file at all, they will only appear in the index contour file.

If you choose to create contour annotations then a string file will be created which contains data suitable for use by the Plotting module for labelling the contour strings, at the mid point of each contour, with the contour values.

String 1 in the annotation string file will contain all the annotation data for the Normal contours while string 2 will contain the annotation data for the index contours.

1. Click the Reset graphics icon . 2. Choose Surfaces > Contouring > Contour DTM file. 3. Enter the information as shown, and then click Apply.


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5. Open annotate1.str. 6. Choose Display > Hide everything. 7. Choose Display > Point > Attributes. 8. Enter the information as shown, and then click Apply.

9. Open index1.str. 10. Open contour1.str


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The results are as shown:


_08b_create_index_contour_file_with_annotations.tcl


Draping a String Over a DTM Calculate The Volume Between Two DTMs.

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Draping a String Over a DTM Task: Draping a Spot Height String over a DTM

1. Click the Reset graphics icon . 2. Open topo1.dtm and then dhcollar1.str. 3. Choose Display > Hide strings > In a layer. 4. Enter the information as shown, and then click Apply.

5. Choose Display > Point > Markers. 6. Enter the information as shown, and then click Apply.

7. Rotate the view of the drill hole collars as shown to enable you to select the markers and not the

DTM.


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8. Choose Surfaces > Drape string over DTM. 9. Click on one of the markers to select the string to drape over the DTM. 10. Enter the information as shown, and then click Apply.

Your results should look like the image shown.


_09a_draping_a_spot_height_string_over_a_dtm.tcl


Task: Draping a Non-Spot Height String over a DTM

1. Click the Reset graphics icon . 2. Open floor1055.dtm. 3. Open centreline.str.

4. Click the icon to view the data in the XZ plane. 5. Choose Display > Point > Markers.


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Notice that centreline.str only contains two points.

7. Choose Surfaces > Drape string over DTM. 8. Click the centreline string. 9. Enter the information as shown, and then click Apply.

Note: In this case, the option to Interpolate New points is ticked to create new points where the string crosses a

triangle edge. 10. Choose Display > Point > Markers. 11. Enter the information as shown, and then click Apply.


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12. Choose View > Data view options > Plan view, and then click the icon to display the DTM triangle edges.

Notice that points have been created at the intersection of the string and DTM triangle edges.

13. Save the string as centreline_draped.str.


_09b_draping_a_non_spot_height_string_over_a_dtm.tcl


Image Draping Calculate The Volume Between Two DTMs.

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Image Draping Task: Drape an image over a DTM.

1. Click the Reset graphics icon . 2. Open eom_pit.dtm.

3. Choose File > Images > Drape an image file over a DTM. Note: You are prompted to Select the triangle of interest.

4. Click anywhere on the DTM. 5. Enter the information as shown, and then click Apply.

Note: The name used for the Registration file must not exist when you are using the register with new points option.


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You are presented with two screens, one containing the DTM and the other containing the image to drape over the DTM.

6. Follow the prompts in yellow at the bottom of the screen to select a series of registration points: firstly in the image, and then in the DTM. Tip: Try to pick points that represent features easily recognisable on both the image and the DTM. Also, pick

enough points to cover the majority of your area of interest. 7. When sufficient registration points have been defined (minimum = 3 points), press ESC to display

the coordinates of your registration points.

8. Click Apply.


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The image is draped over the DTM.

Tip: To give a more realistic view, increase the z scale by a factor of 3.

9. Choose View > Data view options > View scale factors. 10. Enter the information as shown, and then click Apply.

11. Rotate the image to see the full effects of the image drape.


_10_image_draping.tcl


DTM / DTM Intersections Calculate The Volume Between Two DTMs.

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DTM / DTM Intersections Overview:

In this chapter you will learn about upper and lower triangle intersections of DTMs and creating a solid by intersecting 2 DTMs.

Task: Create an Upper Triangles Surface of 2 DTMs

1. Click the Reset graphics icon . 2. Open dump1.dtm. 3. Open topo_dump1.dtm. 4. Choose Surfaces > Clip or intersect DTMs > Upper triangles of 2 DTMs. 5. Enter the information as shown, and then click Apply.

Note: The layer name cannot be the same as any of the current layers.

6. Follow the prompts highlighted in yellow at the bottom of the screen.

The result is a surface representing the waste dump incorporated into the topography.

Note: The DTM appears in a different colour to indicate that it has not been saved.

7. Save the file as upper_surface.dtm.


_11a_upper_triangles_of_2_dtms.tcl



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Task: Create a Lower Triangles Surface of 2 DTMs

1. Click the Reset graphics icon . 2. Open topo1.dtm. 3. Open pit1.dtm. 4. Choose Surfaces > Clip or intersect DTMs > Lower triangles of 2 DTMs. 5. Enter the information as shown, and then click Apply.

6. Follow the prompts highlighted in yellow at the bottom of the screen.

The result is a surface representing the pit incorporated into the topography.

7. Save the file as lower_surface.dtm.


_11b_lower_triangles_of_2DTMs.tcl



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Task: Create Solid by Intersecting 2 DTMs

1. Click the Reset graphics icon . 2. Open topo1.dtm. 3. Open pit1.dtm. 4. Choose Surfaces > Clip or intersect DTMs > Create solid by intersecting 2 DTMs. 5. Enter the information as shown, and then click Apply.

Note: The layer name cannot be the same as any of the current layers.

6. Follow the prompts highlighted in yellow at the bottom of the screen. Note: The upper DTM (topography) must be selected first, followed by the lower DTM (pit).

The result is a DTM solid as shown.

7. Save the file as pit_solid.dtm. 8. Choose Solids > Solids tools > Report volume of solids.


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This will create a note file with the volume of the pit below the topography.


_11c_create_solid_intersecting_2_dtms.tcl

Note: You will need to Apply any forms which are presented.

Documents

Dtm Surfaces