STRINGS & DTM'S

OBJECTIVES

· To learn about Surpac’s graphical file types (*.str & *.dtm).

· To learn how to create surfaces (DTM’s).

· To learn to digitize string data.

· To learn how to display data with Surpac’s styles files.

· To perform surface-to-surface volume calculations.

FILES USED

Files used in this lab exercise are found in the following folder:

C:\ STRINGS_&_DTM'S.LAB\

DISCUSSION

Strings

String data are raw point and line data. Almost all data brought into Surpac will be in this form. All data are stored as strings. A string is a sequence of three-dimensional coordinates delineating some physical feature. As drawn lines in a sketch define essential features, so too do strings. Crests and toes of an open pit mine are strings, as are contours, edges of roads, boundaries of geological zones, the toe of a stockpile, etc. All points defining a single string are stored in string sequence and assigned a common string number. String numbers may be in the range 1 to 32000 inclusive.

Here is an example to illustrate what Strings are:

The string number is a numeric identifier of the feature represented by that string. It may have no significance other than to distinguish one string from another, as is often the case in surveying. More commonly, however, it is the code to identify the purpose of a string, e.g. the string is a boundary string, or defines a pit slope zone, or waste material.

String Kinds

Three kinds of strings are recognized.

Open strings, as in a straight or curved line. If more than one open string exists in a file with the same string number, then these are called open segments of that string and are assigned a segment number.

Closed strings, as in a circle, square or any irregular polygon. A closed string is one whose first and last co-ordinates are the same. If more than one closed string exists in a file with the same string number, then these are called closed segments of that string and are assigned a segment number. This is common in situations where many features, all representing something similar, are logically grouped within a single string identifier, e.g. contours of the same elevation on a topographic map will be assigned the same string number.

A spot height string, being a set of random points linked together by a string number, but outlining no particular feature. The points can be in any order, as the actual line joining them does not represent a feature you can see. Spot height strings are commonly used for recording elevations of points on a surface, or coordinates of bore holes.

Use of String Kinds

In survey applications it is more common to deal with open strings which define discontinuous features, as are found in open pits, with closed strings being used as boundary strings to constrain a volume computation.

Engineers and geologists tend to be more involved with closed strings, such as bench crests and toes, ore outlines etc. Such closed strings may be assigned a thickness and can therefore be used in calculation of both areas and volumes.

String Descriptions

The ability is provided to be able to assign other `non-coordinate' information to each point in a string. This data is called the point description. In surveying, this is usually exactly what it is, e.g. a description or name of a control station. When dealing with closed strings, it is more usual that the point description will contain attributes of the feature enclosed by the string, e.g. the concentration and total salinity of a water sample.

The point description may contain sub-fields, which can be used to address individually for various purposes. These may include:

· storing assays for multiple elements, e.g. total contaminant calculations

· plotting various description sub-fields for a point at different locations about the point.

The description sub-fields are referred to as D1, D2, D3 up to a maximum of D100. They may be generally referred to as D fields.

The D fields are delimited by commas. In the following example

DESCRIPTION = ``TREE, 1.54, HOUSE''

The sub-fields have the values:

D1 =        ``TREE''

D2 =        ``1.54''

D3 =        ``HOUSE''

The total length of the description field may not exceed 512 characters regardless of the number of sub-fields.

String Directions

The convention is to plot a string number at the first point of a string. Depending on how a particular string was created, the order of the points will sometimes give a clockwise direction for the string segment and sometimes an anticlockwise one. This direction of segments is important to closed strings when calculating areas and volumes.

If a closed string is defined in a clockwise direction, it is assumed it represents a positive area; that is an area of inclusion.

If it is defined in an anticlockwise direction, it is assumed it represents a negative area; that is, an area of exclusion.

If an anticlockwise closed segment of a string is contained within a clockwise closed segment, the combination is effectively defining the area between the closed segments.

String Files

Related strings are stored together in ASCII files called string files, identified by an .str extension. A string file can contain up to 32000 different strings

Each file is identified by a two-part name - the two parts are nominated separately in practice, but they are combined to form a filename acceptable to the computer on which the software is being run. The first part is called the Location code. This is an alphanumeric character identifier usually chosen to indicate what the strings in the file represent, e.g. contour, borehole, buildings etc.

The second part is an ID number defining the file as a member of a set of files. This is a numeric character identifier.

For example, a set of files, each containing surveys for an underground mine for the months January, February and March 1990 may be called:

LEV9001

LEV9002

LEV9003

Where LEV is the common location code in each case, and the ID numbers are the year/month code of the individual files containing the surveys.

If you type a decimal number in an ID, for example 1.65:

· the number is rounded to one decimal place, with 0.05 rounded up (that is, 1.65 rounds to 1.7);

· the one-decimal-place number with the decimal point excluded (that is, 17) will be used for referring to the ID;

· refer to the one-decimal-place number, either with or without the decimal point (that is, either 1.7 or 17), when recalling the file.

String File Structure

Each line in a string file is called a record. The first two records are called the header record and axis record respectively. The header record contains data relating to the whole string file such as the location code, date formed and the purpose.

The axis record contains two sets of co-ordinates identified as string number zero, defining a 3-dimensional axis, which is used when taking sections. If no axis has been defined, this record will hold zeros.

The rest of the records in a string file contain points on the strings, with each record having the following structure.

string number

point descriptions

Each field is delimited by a comma. Records containing zeros in all of the first four fields indicate the end of a segment or string. The final record in the string file is a line with a string number of zero and END in the descriptor field.

The following example string file (pump1.str) was created using the GROUNDWATER MODELLING module and contains the definitions of three pumping wells. The file contains five description fields, (D1 - D5): borename, Time pump on (days), Time pump off (days), Pumping rate (kl/d) and Pumping bore radius.

pump
                 ,26-Mar-92,pumping
  wells ,

0, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000
100, 28.275, -47.079, 0.000, recover1 ,0,10000000,500,0.15
100, 117.516, -93.714, 0.000, recover2 ,0,10000000,700,0.2
100, 108.160, -26.973, 0.000, recover3 ,0,10000000,500,0.15
0, 0.000, 0.000, 0.000,
0, 0.000, 0.000, 0.000, END

The second string file (blocks98.str) below shows an example of a string file containing closed segments.

The file was created using the GEOSTATISTICS module and contains regular blocks with a grade calculated using an inverse distance algorithm.

blocks
              ,
  1-May-92,Grade classifications of blocks98.str        
  ,

0, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000
1, 285.000, 115.000, 98.000, 0.035,23.035
1, 295.000, 115.000, 98.000, 0.035,23.035
1, 295.000, 125.000, 98.000, 0.035,23.035
1, 285.000, 125.000, 98.000, 0.035,23.035
1, 285.000, 115.000, 98.000, 0.035,23.035
0, 0.000, 0.000, 0.000,
1, 285.000, 125.000, 98.000, 0.003,47.460
1, 295.000, 125.000, 98.000, 0.003,47.460
1, 295.000, 135.000, 98.000, 0.003,47.460
1, 285.000, 135.000, 98.000, 0.003,47.460
1, 285.000, 125.000, 98.000, 0.003,47.460
0, 0.000, 0.000, 0.000,
2, 35.000, 55.000, 98.000, 4.367,11.462
2, 45.000, 55.000, 98.000, 4.367,11.462
2, 45.000, 65.000, 98.000, 4.367,11.462
2, 35.000, 65.000, 98.000, 4.367,11.462
2, 35.000, 55.000, 98.000, 4.367,11.462
0, 0.000, 0.000, 0.000,
3, 55.000, 55.000, 98.000, 8.941,57.704
3, 65.000, 55.000, 98.000, 8.941,57.704
3, 65.000, 65.000, 98.000, 8.941,57.704
3, 55.000, 65.000, 98.000, 8.941,57.704
3, 55.000, 55.000, 98.000, 8.941,57.704
0, 0.000, 0.000, 0.000,
5, 65.000, 45.000, 98.000, 26.785,36.595
5, 75.000, 45.000, 98.000, 26.785,36.595
5, 75.000, 55.000, 98.000, 26.785,36.595
5, 65.000, 55.000, 98.000, 26.785,36.595
5, 65.000, 45.000, 98.000, 26.785,36.595
0, 0.000, 0.000, 0.000,
0, 0.000, 0.000, 0.000, END

DTM’s

Digital Terrain Models or DTM’s are how Surpac models surfaces. Surfaces are used in Surpac for such things as 3D visualization & calculating volumes. Most any superficial feature can be modelled as a DTM: natural topography, lithological contacts, bedrock/overburden contact, or water table are such examples. DTM’s must come from String data. String files contain the raw data, where as DTM files contain a mapping of trios of points in the String file that constitute a triangle. DTM’s 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 does not exist. Another rule as far as DTM’s are concerned is that DTM’s cannot fold back on themselves. That is, a DTM cannot have multiple Z values for a given XY coordinate.

Styles Files

Styles files are used to tell Surpac how to display String and DTM data. The default styles file is called styles.ssi. Styles files let the user specify the following attributes:

· a label for the style for legend purposes

· drawing method - i.e. lines, markers, attribute values, etc.

· line colour

· line thickness

· line pattern

· face colour

· specular reflectance colour - the colour of the shiny spots

· transmission colour for transparency effects

· gloss effects - the size of the shiny spots

· face pattern

· edge colour

· edge thickness

· edge pattern

· text colour

· marker symbol

· marker size

· text characteristics, font, size, slant and path

Every time a String file is saved the current styles file is associated with it so that every time it’s opened it uses that styles file automatically. If that styles file is not found it uses the default styles.ssi.

Digitizing

A very common way of imputing data into Surpac is to digitize.  You may use the mouse or a digitizing tablet for digitizing data.  You would have learned these functions on the Main toolbar in the previous lab:

	Change Digitizer point attributes
	Digitize at Cursor Location
	Digitize at Selected Point
	Close Digitized Segment
	Start a New Segment
	Digitize by Following Segment
	Digitize Midpoint

All the digitizing functions are found in the CREATE, DIGITIZE menu.  The elevation of any current digitizing may be defined in CREATE, DIGITIZE, PROPERTIES or by using the  button.  Any digitizing you do can always be edited using the Editing functions learned in the previous lab.

ASSIGNMENT

Use the digitizing functions to finish the topography in the file contours2.str. There are several contours missing from the 219 elevation to the 243 elevation every 3m. The completed file should look similar to the following diagram.

Use the

function to digitize several contour lines in the Northwest corner of the topography. You may use the

function to select the appropriate elevation of the digitized segments. Save & submit this file.

For the file “topo1.str”, modify it’s styles file so that the lines and the elevation are displayed every 200m. Plot & submit this file.
For the file “topo1.str”, modify it’s styles file so that the data are displayed as markers (points). Plot & submit this file.
Use the function CUT AND FILL BETWEEN DTM’S from the VOLUMES menu to calculate the surface-to-surface volume between pit1.dtm & topo1.dtm. Submit the resulting volume report (text file).

PROCEDURE

Use the digitizing functions to finish the topography in the file contours2.str.

Choose the button from the toolbar to specify the properties for the digitizing. Fill the form as follows:

This will initialize the digitizing so that you’re creating points in string #1 at elevation 219.

Choose the button from the toolbar to digitize a point at the cursor location. The prompting message should ask you to digitize a point using the mouse. Click to digitize a mouse at approximately the location indicated in the following diagram:

Digitize first point here.

Once the first point is digitized, keep clicking to add new points. Follow the general trend of the lower contour line (5580). The data should look approximately as follows:

New digitized segment.

Repeat steps ‘a’ to ‘c’, incrementing the digitizing elevation by 3m until you reach the 243 elevation.

For the file “contours2.str”, modify it’s styles file so that the lines and the elevation are displayed every 200m. Plot & submit this file.\

From the CUSTOMIZE menu choose Display Properties, Strings and points.
Fill the subsequent form as follows:

For the file “contours2.str”, modify it’s styles file so that the data are displayed as markers (points). Plot & submit this file.

From the CUSTOMIZE menu choose Display Properties, Strings and points.
Fill the subsequent form as follows:

Use the function CUT AND FILL BETWEEN DTM’S from the VOLUMES menu to calculate the surface-to-surface volume between pit1.dtm & topo1.dtm. Submit the resulting volume report (text file).

From the menu Volumes, choose Cut and fill between DTM’s.
Fill the subsequent form as follows:

tutorial

Senin, 30 Maret 2015