This Client Server article is republished in its entirety from 2002 for reference purposes.
By Patsy Gant, Bentley Civil Engineering Professional Services Technical Documentation Coordinator; Bentley Huntsville, Alabama
30 May 2002
Incorporating pre-existing survey data into a new software application can be a time-consuming task. Fortunately, the InRoads suite of civil engineering solutions makes it easy to incorporate existing data into a new DTM.
Training and reference materials for Bentley's powerful software illustrate very clearly how users can follow a prescribed path and the resulting design will address their specific needs. But what about users who have already committed a good portion of time to a project prior to purchasing a Bentley software solution? Obviously, their situation doesn't fit into the "prescribed path." What happens to their investment in time, money and resources? Is it lost-thrown away?
Work already completed as a stage of a project must be recognized and utilized. Yet incorporating such pre-existing data into a new software application to develop an existing digital terrain model (DTM) can be one of the more time-consuming tasks in a civil engineering project. Fortunately, the InRoads suite of civil engineering solutions meets this need and allows users to incorporate existing data into a new DTM.
In civil engineering, the DTM provides the actual 3D information upon which all of the roadway design can be based. InRoads specifically enables users to develop DTMs via linearly connected points that form breaklines or other linear features in the DTM. Linear features enable users to control the way triangulation is performed, by direct linear interpolation and addition of computed points between linear vertexes (according to Delauney's Criteria). In addition, linear features prevent triangles from crossing, which significantly affects the final outcome of the existing DTM.
Guidelines for Collecting Linear Features
Data collected from field surveys enables users to generate DTMs. Understanding this makes it easier to collect new data in a defined format, a point-to-point connection via control codes method, that allows easy point-to-point linear connections. This process requires users to code each linear feature with a unique feature code name (TD for top of ditch, for example) and specify where the feature begins with a control code (ST for start, for example). Users must sequentially observe each point along the linear feature to enable automated linear feature creation of InRoads and InRoads Survey. If the points are not located sequentially with the proper feature and control coding, the resulting connection of points will zigzag from point to point and not create the desired linear feature for the DTM.
Using Pre-existing Data for Linear Feature Collection
Often, field data has been collected using the point-to-point method identified above, but multiple rod handlers who were "leapfrogging" may have collected the points between shots. When the points are connected with the control codes specified in scenarios such as this, the zigzag effect is very evident and the resulting line work is not very useable. It is necessary, therefore, to either sort the data in a sequential manner or just throw it out and recollect the information. Frankly, the latter should never be an option, so the logical action is to connect the points in a sequential manner.
Existing points may have also been collected on different days and saved to numerous distinct raw data files. Their one common denominator is that the feature code of the linear element is consistent. An example of this consistency could be the right and left edges of pavement: LEOP (left edge of pavement) and REOP (right edge of pavement).
Evaluating the Options
As points are provided from multiple field surveys, users must choose whether to attempt to sync up the observations that created the points. In this scenario, only the point values are necessary, so users would opt not to sync up. Point values are static points generally found in the geometry (.alg) file.
The Point-To-Point Connection Via Control Codes method is accomplished using the InRoads Survey fieldbook. The static points that are located in the geometry file must be sequentially imported into the fieldbook to create the proper linear feature(s). Once the features have been sequentially imported, it is possible to create the desired DTM.
DTM Methodology
The following procedure outlines the steps required to create a linear feature-based DTM from old or existing data:
- Process existing field data and store it as point data into the Cogo buffer of the InRoads geometry (.alg) file, ensuring that all points are placed in one alignment project.
- From InRoads, create a new horizontal alignment.
- Select Geometry > Horizontal Regression > Add Horizontal Regression Points and deposit the desired points into the regression buffer. Be certain to use the appropriate filters and begin point when creating the point listing.
- Review your actions to ensure that all of the desired points have been added to the regression buffer.
- Using the Geometry > Horizontal Curve Set > Add PI command, add a linear element that starts before the regression points and ends after them. This is to be used as a reference line in the following steps.
- Select Tools > XML Reports > Geometry tab and set the values on the XML Reports dialog:
1. For the Horizontal Alignments Include field, enter the name of the regression alignment created in Step 5.
2. Toggle Include Horizontal Event Points to On.
3. For File Name, place the file wherever your project is located. It will have an extension of .xml. - Before converting the .xml report to the desired format, copy c:\Bentley\..\XML Data\slewdiagram.xsl and rename it retrofit.xsl.
- Using the editor of choice, edit the retrofit.xsl to have the following key items:
- Excerpt 1
<thead>
<th align="center">Point No </th>
<th align="center">Northing</th>
<th align="center">Easting</th>
<th align="center">Elevation</th>
</tr>
</thead>
</table>
<xsl:call-template name="Data"/>
</xsl:template>
<!-- Data -->
<xsl:template name="Data">
<hr width="90%" align="left"/>
<xsl:variable name="startStation" select="Start/station/@externalStation"/>
<xsl:variable name="endStation" select="End/station/@externalStation"/>
<table width="90%" cellpadding="4">
<colgroup span="4">
<col width="5%"/>
<col width="5%"/>
<col width="5%"/>
<col width="5%"/>
</colgroup>
<xsl:for-each
select="ancestor::*/HorizontalEventPoints/HorizontalRegressionPoints/HorizontalRegressionPoint /HorizontalEventPoint/Geometry
Point">
<xsl:if test="(station/@externalStation >= $startStation) and (station/@externalStation <=
$endStation)">
<tbody>
<tr>
<td align="center">
<xsl:value-of select="@name"/>
</td>
<td align="center">
<xsl:value-of select="@northing"/>
</td>
<td align="center">
<xsl:value-of select="@easting"/>
</td>
<td align="center">
<xsl:value-of select="@elevation"/>
</td>
<!-- Retrofit Linear Sorter Column-->
</tr>
</tbody>
The following key lines report on point name, northing, easting and elevation:
Excerpt 2
<xsl:for-each
select="ancestor::*/HorizontalEventPoints/HorizontalRegressionPoints/HorizontalRegressionPoint/HorizontalEventPoint/GeometryPoint">
<xsl:if test="(station/@externalStation >= $startStation) and (station/@externalStation <=
$endStation)">
<tbody>
<tr>
<td align="center">
<xsl:value-of select="@name"/>
</td>
<td align="center">
<xsl:value-of select="@northing"/>
</td>
<td align="center">
<xsl:value-of select="@easting"/>
</td>
<td align="center">
<xsl:value-of select="@elevation"/>
</td>
<!-- Retrofit Linear Sorter Column-->
</tr>
</tbody>
10. After creating the above retrofit.xsl file, use the Tools > View XML Reports command with the following settings:
For Source, key in the filename for the newly created .xml.
For Format, key in c:\Bentley\..\XML Data\retrofit.xsl to load the appropriate report. This automatically creates the desired report, which will contain: Point Name, Northing, Easting, Elevation and Code.
Users should know that there are actually two output techniques for such reports. The first technique contains the point name, northing, easting, elevation and feature code. The first line in this output will also contain a start control code, which is embedded in the xsl. format.
The second output technique contains the point name, northing, easting, elevation and pen code. In this instance, the first point will have a "1" for the pen code. All subsequent points will have a "0."
11. After the report has been created, use the InRoads Survey File > Import > Survey Data command to import the data into a survey field book. You will need to make minor edits to the points to add a start control code at the beginning of each line.
Another option is to import the newly created report directly into the InRoads surface as an ASCII file, specifying a linear feature type when importing the file.
12. After repeating these steps for all of the appropriate DTM strings, you can generate a finished linear feature-based DTM from your existing data.
Please note that only excerpts of the xsl. code have been provided in this documentation. Detailed information regarding the code and its use with either of the report types discussed in this article can be accessed by Bentley SELECT subscribers on the Bentley Civil KnowledgeBase at http://selectservices.bentley.com.
See Also
InRoads Product TechNotes FAQs And Support Video Clips
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