SUR 4201L - Lab 3

 

 

 

Topography

 

OBJECTIVE

 

The goal of this lab is to create a continuous elevation surface model of the Loxahatchee project area.  Given known spot elevations in the form of X, Y, Z coordinates, you will use GEOPAK to create a triangulated irregular network (TIN).  This TIN file will be used all semester for interpolation heights when creating the vertical alignment, drawing cross sections, calculating earthwork and more.

 

STEPS

 

Download the topo.txt and save it in your folder in the public directory. This file contains the known X, Y and Z coordinates of all vertices along contour lines.

 

At this point you should have a plain text file with 3 columns for X, Y and Z separated by commas.  Remove the X, Y, Z column headings (delete entire first row).  Now we have to convert this file into a format GEOPAK will work with directly. Create a new topo.dgn file.  Then go under:

 

  1. Applications
  2. GEOPAK ROAD
  3. DTM Tools
  4. A toolbox will open. Click on the upper left-hand yellow icon to open the DTM menu bar.  The GEOPAK DTM menu bar will pop up.

 

Now to import the XYZ ASCII coordinate file (the topo.txt file) into the GEOPAK data format (.dat):

 

  1. Extract
  2. XYZ
  3. Enter the input file name (topo.txt), which is the comma-delimited file.
  4. Enter the output file name (topo.dat). Use a .dat extension.
  5. Set the Delimiter to comma (or whatever your delimiter is).
  6. Set the Comment Delimiter to none.
  7. The contents of your file can now be seen. Click on the first record.
  8. Specify the column order (X = Easting, Y = Northing, Z = Elevation)
  9. Process.
  10. Click OK to any warning messages that may appear.
  11. Close the window when complete.

 

Next we want to create a TIN file from our dat file:

 

  1. Build
  2. Triangles
  3. Type in the data file name (topo.dat), which was created above.
  4. Type in the output TIN file name with a .tin extension (topo.tin)
  5. Process.
  6. Close the window after MicroStation reports ‘Build Triangles Completed’.

 

You now have a complete TIN file, which GEOPAK can use to interpolate contours and calculate elevations anywhere in the study area.

 

Finally to display our contours in MicroStation:

 

  1. Load
  2. DTM Feature
  3. Set the Load File option to TIN.
  4. Type in the name of you TIN file that was just created (topo.tin).
  5. Uncheck the display only box and Graphic Group box.
  6. Select Contours and double click so the DISPLAY column reads ON.
  7. Set the Major Interval to 25 and the Minor Interval to 5.
  8. Click Read. This updates the Minimum and Maximum Z values that will be displayed by directly reading your TIN file.
  9. Turn on other features you would like to see drawn (hull, triangles, spots).
  10. Load.
  11. Close the Load Contours window.

 

Use Fit View if you cannot see your contours. Note that you cannot turn off the contours by simply turning the DISPLAY option to OFF. This only controls what will be drawn when the Load button is used. To remove your contours you must use the fence-delete tool. They can always be reloaded into any DGN as long as you have the TIN file in your working directory.

 

Your now have a complete representation of your topography. In future projects GEOPAK will reference your TIN file.

 

When finished, close MicroStation and backup all the files created in this lab.

 

 

Assignment # 1

 

Complete assignment # 1 and submit it along with submission # 1 on the due date.

Posted on the website with the required information and materials to work with under the Assignment link.

 

 

 

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 Last updated: 1/24/2005