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Construction surveying requires a variety of measurements and knowledge of the surrounding area.Although using a single shapefile can aid in identifying where certain survey points should be within an area or along a road,it is limited in its ability to describe the natural land features.In the example below,we show how information can be extracted using both a shapefile and LAS point cloud to begin surveying for a mock road upgrade.This process is much more realistic for surveyors and engineers that may require ground data prior to any sort of construction.We will demonstrate how to buffer the road and create cross sections that are evenly spaced along a highway with the LAS point cloud data.
The steps below outline how to use a shapefile with a point cloud to identify cross sections along a section of highway.Shapefiles are useful for understanding the geometry of a feature,but the addition of LAS data provides information about both the feature and the surrounding area with elevation data.This means in addition to locating equally spaced cross sections,you will also have a better idea of landscape that you are working in,which is extremely important when improving infrastructure.
Steps:
Isolate Area of Interest
Retrieve LAS Ground Points
The images below show the resulting output point cloud cross sections in 2D and 3D along the section of highway that we were interested in.In image a.you can see that the cross sections were accurately drawn to be perpendicular at each 500 unit interval so each cross section is on a slightly different angle than the others.In image b.you can see that by using a 3D point cloud to represent each cross section we get a better sense of what the highway and surrounding area look like in reality versus using 2D shapefiles.
a.b.
Two-dimensional profiles of cross sections can help to emphasize the natural landscape in the area that you will be working in.With a highway improvement,this can help with understanding what kind of work will be required for widening a highway or which locations will require more or less analysis prior to construction.For example,if you can see in a profile that the cross section is quite steep,you will know that this location may require further analysis to ensure that the ground is stable.The steps below use the previously created cross-section slices to create profiles.This example will work off the previous workspace by adding more transformers following Step 14 which ended with a Counter transformer.
Steps:
Rotate Slices and Add Attributes
Hi,
this seems a pretty fine 亚搏在线workflow.I'm interested in the
"LIDAR_Slices.fmwt"...could you attach it please?
Greetings from Germany
Thorsten
Hi@schefthI have attached the template to this article (sorry it was missing).
Hi,
the template works really fine and does exactly what I need
for my project.
But I still have a question: As an extra process,you created
profiles along the cross-sections.I also done this by using a
very small buffer size (Buffer_2) of 1cm and after that I created
a single line with the "PointConnector" and the "Generalizer".
This works good,but there is still this maximum expansion of 1cm
in the Y-Direction.How did you realize the 'flat' profiles?Did you
project the points of the slice to an plain which is part of
the cross-section-line (at right angle to the middle-line
of the road)?How did you realize this?
Thanks
Thorsten
Hi Thorsten,
I am attaching a workspace that contains the part where I create the profiles (which,as I aid in the article,was excluded from the original download).It was 5 years ago when I created the workspace,but if I recall correctly,the idea was to take a "thick" slice,swap Y and Z (CoordinateSwapper),and then eliminate z (2DForcer).As result,all points line up on a single line and can be sorted (Sorter) and connected (PointConnector).
I hope this answers your question.If you have more questions,please let me know.
Converting Point Clouds to Surface Models Using the PointCloudLASClassifier
Getting Started with Point Clouds
What is a Point Cloud?What is LiDAR?
Using LIDAR Waveform Attributes in FME
Thinning and Combining Point Clouds
Creating Boundary and Point Features from a Point Cloud
Viewing and Inspecting Point Clouds
Converting Point Clouds to Surface Models without Classification
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