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Any referenced datasets can be downloaded from "Module downloads" in the module overview.
Transcript
00:00
NARRATOR: Welcome to the second objective in the
00:02
"How to Manage Large Surfaces Efficiently" course.
00:06
This objective is controlling LOD with detail and surround
00:10
surfaces.
00:12
LOD stands for the Level of Detail,
00:15
and it is the resolution of the model object.
00:18
Existing conditions surfaces can have different LODs
00:21
depending on the captured data and the purpose of the model.
00:25
Surface models are typically used for detail design
00:29
and construction purposes or surrounds
00:32
for visualization, hydrology, environmental and background
00:36
effects.
00:38
Model resolution has a huge effect
00:40
on the size of the model object and consequently,
00:43
the performance of the software.
00:46
You must always ask, what is the purpose of the model
00:49
and what are the specifications of the original data?
00:52
Remember, more is not always better.
00:56
Do you really need to have resolution
00:58
the size of a quarter, or major elevation changes less than an
01:02
inch, or 2 and 1/2 centimeters?
01:04
And are you doing the grading with a shovel?
01:07
Or are you using grading machinery?
01:10
We learned in the last objective,
01:11
to assure good performance in Civil 3D,
01:14
surfaces need to be limited in the number of points.
01:17
TIN surfaces should be limited to 1 and 1/2
01:20
to two million points maximum, and grid surfaces
01:24
need to be 1 billion points or less.
01:27
In today's industry practices, existing conditions data
01:30
capture often results in point clouds.
01:33
These are huge, and they exceed the surface size limits.
01:37
To get good representations of the existing topography,
01:41
surfaces must be cropped or bounded into meaningful regions
01:46
or swaths, and they need to be reduced or simplified
01:50
to the proper resolution for the intended purpose.
01:54
LOD has an impact on file size.
01:57
If we take a look at the lower left image,
01:59
we can see a surrounds surface and a detailed swath
02:05
surface that has several areas of interest.
02:10
And by looking at the file size, we
02:13
see that the detail surface is over five times larger,
02:17
even though it encompasses a much smaller area.
02:21
The resolution is shown on the lower right.
02:24
The surrounds surface has a two-meter resolution,
02:29
and the detail surface has a half meter resolution.
02:35
And the LOD impact on surface size,
02:38
meaning the number of points on a surface,
02:41
if we look at a surrounds surface, in this example,
02:44
we have a 0.45 million points.
02:47
That's less than half a million points.
02:50
The resolution is a three-meter grid.
02:54
The details surface shows a much smaller area,
02:57
and it has 1.1 million points, and the grid is 0.14 meters.
03:04
In this example, the surrounds surface,
03:06
even though it's much smaller, has enough information
03:09
for the purpose of hydrology and backgrounds visualization.
03:14
And the detail surface, having a resolution of 0.14 meters
03:18
is fine for detailing the existing conditions.
03:22
Point cloud data capture density affects the surface resolution.
03:26
You must know how you will ultimately
03:28
use your scan data to know how detailed your scan must be.
03:33
Here we show some examples of point cloud density going
03:36
from the coarsest on the left to the most dense on the right.
03:40
And the images at the bottom show the respective surface
03:44
model resolution that comes from these point cloud densities.
03:48
In our example, the surrounds surface
03:51
represents a low level of detail.
03:54
The original point cloud contain just under 20 million points.
03:59
The classified ground only points were 6 million,
04:03
and this represented a 0.82 meter grid spacing resolution
04:08
from this original grid surface, the surrounds grid
04:12
was created by exporting at a
04:17
resulted in 0.45 million points, which
04:21
is a significantly lower amount of points
04:23
than the original surface.
04:26
This also represents using only 2.3%
04:30
of the original point cloud data.
04:32
This gives us a surface that is good for the intent
04:36
of background visualization, flood and slope
04:39
analysis, and some preliminary design tasks.
04:43
Here's a demonstration on changing the resolution
04:46
of the surrounds surface.
04:48
We begin in the surrounds surface.
04:50
Start drawing.
04:52
And we'll create the first grid surface
04:55
using the GeoTIFF that was extracted
04:58
from the classified ground points in the point cloud.
05:08
Looking at the surface properties,
05:11
we can see that the name of the surface has a prefix of grid
05:15
from DEM file.
05:18
And if we look at the statistics,
05:20
we see that we have just over 6 million points.
05:25
The grid resolution is 0.823 meters.
05:33
Notice that we're using a level of detail that's turned on,
05:37
so we might not be seeing all of the surface contour details.
05:41
From the surface, we're going to export a DEM,
05:45
and I'm going to give it a file name of Surrounds Surface 3m
05:50
Grid.
05:51
We'll make sure that we changed the grid spacing on the Export
05:55
DEM interface to represent 3 meters,
05:59
and we'll sample the surface.
06:01
Add a grid point.
06:03
This GeoTIFF file does not take a long time to generate.
06:09
Then we return to the surface collection
06:11
and use the file that we just made
06:14
to create the surrounds surface grid at 3 meters.
06:23
Let's compare the statistics, and we
06:25
see that now, this surface has only 0.451 million points,
06:32
and the grid is at
06:37
I'll change the surface style so that we can zoom in and compare
06:42
the two different contour maps.
06:44
Before I do that, I will put a boundary
06:48
on the large surface and the small surface
06:52
so this will limit the data that has to be computed,
06:55
and we will have better performance in this drawing.
07:11
Now I'll select the named view and zoom in,
07:15
and we can compare the contours from the two
07:18
different resolution surfaces.
07:20
Now let's look at the detail surface.
07:23
We want to take a grid surface and turn it into a TIN surface.
07:28
This is because TIN surfaces can be edited.
07:31
The original point cloud for the detail surface
07:33
was 6.3 million points.
07:38
as ground only points.
07:40
This represents a resolution of 0.14 meter grid spacing.
07:45
We will create a TIN surface using the GeoTIFF
07:48
as the build data.
07:50
And because this is a TIN surface,
07:52
it is acceptable to have a surface of 1 million points.
07:57
The TIN surface will allow us to add manual edits
08:00
so that the surface intent can be
08:02
used for the purpose of detail design, structure
08:06
placement, and settings out information for construction.
08:10
This demonstrates how to create a TIN surface using a GeoTIFF
08:14
file.
08:15
We begin by creating a surface, and the type in the upper left
08:20
is TIN surface.
08:22
I will give the surface a name, and then
08:27
we expand the surface collection,
08:30
and we can see that we have a list of definition options.
08:34
I will use DEM files, and I will browse
08:38
to the GeoTIFF that represents the ground only
08:43
points from our point cloud.
08:55
Now looking at the surface statistics.
08:58
we see that the number of points is just over 1 million points.
09:04
And now that this is a TIN surface,
09:06
this allows us to do additional editing
09:08
by adding breaklines, contours, and other information.
09:14
Remember, to improve the representation of existing
09:17
conditions, often we need to do manual editing
09:21
and even add more data.
09:23
We can add breakline data, which would be proximity
09:27
or stepped offsets.
09:28
We can add contour data and other data types,
09:32
such as coeval points and even 3D entities.
09:36
This completes the objective of controlling LOD with detail
09:40
and surrounds surface.
Video transcript
00:00
NARRATOR: Welcome to the second objective in the
00:02
"How to Manage Large Surfaces Efficiently" course.
00:06
This objective is controlling LOD with detail and surround
00:10
surfaces.
00:12
LOD stands for the Level of Detail,
00:15
and it is the resolution of the model object.
00:18
Existing conditions surfaces can have different LODs
00:21
depending on the captured data and the purpose of the model.
00:25
Surface models are typically used for detail design
00:29
and construction purposes or surrounds
00:32
for visualization, hydrology, environmental and background
00:36
effects.
00:38
Model resolution has a huge effect
00:40
on the size of the model object and consequently,
00:43
the performance of the software.
00:46
You must always ask, what is the purpose of the model
00:49
and what are the specifications of the original data?
00:52
Remember, more is not always better.
00:56
Do you really need to have resolution
00:58
the size of a quarter, or major elevation changes less than an
01:02
inch, or 2 and 1/2 centimeters?
01:04
And are you doing the grading with a shovel?
01:07
Or are you using grading machinery?
01:10
We learned in the last objective,
01:11
to assure good performance in Civil 3D,
01:14
surfaces need to be limited in the number of points.
01:17
TIN surfaces should be limited to 1 and 1/2
01:20
to two million points maximum, and grid surfaces
01:24
need to be 1 billion points or less.
01:27
In today's industry practices, existing conditions data
01:30
capture often results in point clouds.
01:33
These are huge, and they exceed the surface size limits.
01:37
To get good representations of the existing topography,
01:41
surfaces must be cropped or bounded into meaningful regions
01:46
or swaths, and they need to be reduced or simplified
01:50
to the proper resolution for the intended purpose.
01:54
LOD has an impact on file size.
01:57
If we take a look at the lower left image,
01:59
we can see a surrounds surface and a detailed swath
02:05
surface that has several areas of interest.
02:10
And by looking at the file size, we
02:13
see that the detail surface is over five times larger,
02:17
even though it encompasses a much smaller area.
02:21
The resolution is shown on the lower right.
02:24
The surrounds surface has a two-meter resolution,
02:29
and the detail surface has a half meter resolution.
02:35
And the LOD impact on surface size,
02:38
meaning the number of points on a surface,
02:41
if we look at a surrounds surface, in this example,
02:44
we have a 0.45 million points.
02:47
That's less than half a million points.
02:50
The resolution is a three-meter grid.
02:54
The details surface shows a much smaller area,
02:57
and it has 1.1 million points, and the grid is 0.14 meters.
03:04
In this example, the surrounds surface,
03:06
even though it's much smaller, has enough information
03:09
for the purpose of hydrology and backgrounds visualization.
03:14
And the detail surface, having a resolution of 0.14 meters
03:18
is fine for detailing the existing conditions.
03:22
Point cloud data capture density affects the surface resolution.
03:26
You must know how you will ultimately
03:28
use your scan data to know how detailed your scan must be.
03:33
Here we show some examples of point cloud density going
03:36
from the coarsest on the left to the most dense on the right.
03:40
And the images at the bottom show the respective surface
03:44
model resolution that comes from these point cloud densities.
03:48
In our example, the surrounds surface
03:51
represents a low level of detail.
03:54
The original point cloud contain just under 20 million points.
03:59
The classified ground only points were 6 million,
04:03
and this represented a 0.82 meter grid spacing resolution
04:08
from this original grid surface, the surrounds grid
04:12
was created by exporting at a
04:17
resulted in 0.45 million points, which
04:21
is a significantly lower amount of points
04:23
than the original surface.
04:26
This also represents using only 2.3%
04:30
of the original point cloud data.
04:32
This gives us a surface that is good for the intent
04:36
of background visualization, flood and slope
04:39
analysis, and some preliminary design tasks.
04:43
Here's a demonstration on changing the resolution
04:46
of the surrounds surface.
04:48
We begin in the surrounds surface.
04:50
Start drawing.
04:52
And we'll create the first grid surface
04:55
using the GeoTIFF that was extracted
04:58
from the classified ground points in the point cloud.
05:08
Looking at the surface properties,
05:11
we can see that the name of the surface has a prefix of grid
05:15
from DEM file.
05:18
And if we look at the statistics,
05:20
we see that we have just over 6 million points.
05:25
The grid resolution is 0.823 meters.
05:33
Notice that we're using a level of detail that's turned on,
05:37
so we might not be seeing all of the surface contour details.
05:41
From the surface, we're going to export a DEM,
05:45
and I'm going to give it a file name of Surrounds Surface 3m
05:50
Grid.
05:51
We'll make sure that we changed the grid spacing on the Export
05:55
DEM interface to represent 3 meters,
05:59
and we'll sample the surface.
06:01
Add a grid point.
06:03
This GeoTIFF file does not take a long time to generate.
06:09
Then we return to the surface collection
06:11
and use the file that we just made
06:14
to create the surrounds surface grid at 3 meters.
06:23
Let's compare the statistics, and we
06:25
see that now, this surface has only 0.451 million points,
06:32
and the grid is at
06:37
I'll change the surface style so that we can zoom in and compare
06:42
the two different contour maps.
06:44
Before I do that, I will put a boundary
06:48
on the large surface and the small surface
06:52
so this will limit the data that has to be computed,
06:55
and we will have better performance in this drawing.
07:11
Now I'll select the named view and zoom in,
07:15
and we can compare the contours from the two
07:18
different resolution surfaces.
07:20
Now let's look at the detail surface.
07:23
We want to take a grid surface and turn it into a TIN surface.
07:28
This is because TIN surfaces can be edited.
07:31
The original point cloud for the detail surface
07:33
was 6.3 million points.
07:38
as ground only points.
07:40
This represents a resolution of 0.14 meter grid spacing.
07:45
We will create a TIN surface using the GeoTIFF
07:48
as the build data.
07:50
And because this is a TIN surface,
07:52
it is acceptable to have a surface of 1 million points.
07:57
The TIN surface will allow us to add manual edits
08:00
so that the surface intent can be
08:02
used for the purpose of detail design, structure
08:06
placement, and settings out information for construction.
08:10
This demonstrates how to create a TIN surface using a GeoTIFF
08:14
file.
08:15
We begin by creating a surface, and the type in the upper left
08:20
is TIN surface.
08:22
I will give the surface a name, and then
08:27
we expand the surface collection,
08:30
and we can see that we have a list of definition options.
08:34
I will use DEM files, and I will browse
08:38
to the GeoTIFF that represents the ground only
08:43
points from our point cloud.
08:55
Now looking at the surface statistics.
08:58
we see that the number of points is just over 1 million points.
09:04
And now that this is a TIN surface,
09:06
this allows us to do additional editing
09:08
by adding breaklines, contours, and other information.
09:14
Remember, to improve the representation of existing
09:17
conditions, often we need to do manual editing
09:21
and even add more data.
09:23
We can add breakline data, which would be proximity
09:27
or stepped offsets.
09:28
We can add contour data and other data types,
09:32
such as coeval points and even 3D entities.
09:36
This completes the objective of controlling LOD with detail
09:40
and surrounds surface.
The DEM file is the result of filtering the classified point cloud to create a grid file of only ground surface points, which will save a lot of editing and clean-up time to get a good representation of the existing topographic features of the large project site.
The grid spacing of the original surface created from point cloud data has a 0.823 meter spacing which is too detailed for the purpose of a large surrounds surface and the number of points exceeds the maximum point limit of 1 million points. Exporting a new DEM from this surface will enable the grid spacing to be set at a much larger spacing which will have a benefit of also reducing the number of surface points to a value well beneath the maximum limit.
A new DEM surface to be used as the surrounds surface is created from the newly generated GeoTif file. This surface will be much smaller in point number size because of the 3.0 meter grid spacing, however the surface remains with enough resolution to be used for the surrounds surface purposes.
Repeat steps 1 and 2 in Task 2 to see that the number of points in the new surface abject named: Grid from DEM file Surrounds Surface 3m Grid is just over 450 thousand points, which is below the 1 million point maximum.
Using classified point cloud data to build surface usually results in a Grid type surface which is limited to one million points. If a TIN surface is created then the maximum number can be increased to 1.5 to 2 million points. An additional benefit to using a TIN surface is the additional edits that can be made to further refine the definition.
On the Statistics tab note the number of points is just over 1 million. And because this is a TIN surface now additional edits, such as adding breaklines, can be made to refine the definition.
In this drawing we have two surfaces: one representing the large area of surrounds and the other representing the details needed in an area of construction, modification, or rehabilitation. In both cases it is important to limit the number of points so that overflow: .MMS or .GRD files are not generated.
You do not need to save this Civil 3D drawing.
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