Following on from Case Study 7, which used LiDAR, Aerial Photography and GNNS to carry out a golf course survey, this Case Study looks at the need to re-design a practice ground introducing a new tee-off area and chipping green. We’re going to combine GNNS with our own drone survey to create visuals and quantities for decision makes at the golf club.
Longcliffe Gold Club - Updating Practice Ground
Part of the original survey was used to give an overall view of the new design, as shown here.
What we need to establish are visuals and quantities for a new practice ground arrangement, including a new teeing and area and chipping green.
The starting point was to carry out a survey of the existing practice area. We could and did use the LiDAR survey previously mentioned, but this was supplemented with a GNNS survey which confirmed that the levels were compatible.
Since AiC had recently purchased a drone this was also used to generate up to date georeferenced photography and check levels which again compared well. Learning and very enjoyable experience by the AiC support team.
Drone Survey of Practice Ground
Space on the existing practice ground is restricted and the ground had a significant curvature so an elevated teeing box was proposed, raising the viewing area so long drives could be seen landing. A new chipping area was also proposed, maximising the number of golfers using the practice ground at any one time.
Low-velocity range balls would be used on the practice ground, so the maximum drive would be less than 200yds and would comfortably fit the area provided. This positioned the elevated tee below a small rise, leaving space for the chipping area, as identified below.
Practice Ground Long Section
Preliminary Design – Tee Box
A 10m x 34m outline representing the new tee box location was staked out together with the extents of a chipping green and then surveyed using GNSS. This is stored in the Coordinates area, as 29-06-2018_TS (Andrew).
The next stage is to create a model. Right-click over Models on the Project Tree and select New Normal.
Creating a New Model
Call the model 10m Tee Box and the Scale to 100. In the Points Tab, move the survey from the Available to the Selected window. This new model is where we will be creating our designs, calculating volumes and drawing sections.
Note: the integrated environment of n4ce allows you to work in either CAD with its advanced drafting tools, or directly in a model. Tools are available for converting from CAD to model strings and vice versa.
We will be using CAD tools to initially sketch out the design. This can be done in a separate CAD folder using the model as a backcloth or, as we will do here, using the model's Dedicated CAD Backcloth. After going into model graphics, select the combined (model and CAD) icon This will show the survey points as a backcloth, but in the CAD environment. Also, add the image Geoimage.ecw as a backcloth. This is supplied as an external file and may need to be loaded.
A symbol has already been created with the correct sizing for the tee box, called the 10x34 Box. This is a two-point symbol and can be attached and aligned to the bottom left reference points. The top 5 points forming the outline of the chipping green can be joined using a multi-segment line, then curve fitted, as shown below. The lone point is where the green keeper wanted the bottom of the batter slope to be.
Note, points were positioned approximately giving some freedom to move the design, if necessary. It was later decided to update the teeing bund to 15m wide which would provide for up to ten 3m wide driving bays and a 2m walkway along the back and side. But for this exercise, we will stick to the original dimensions.
Sketching Out Outlines in Dedicated CAD Backcloth
Before leaving the dedicated CAD backcloth, explode the rectangle symbol. We will use this outline to form a top of batter string.
The ground falls from the right to left in the above image and it was decided to make the teeing box level at 84m to approximate the existing ground level at the right edge. We will also add a 10cm fall from front to back to remove any standing surface water.
Returning back to the model environment, the next stage is to create design strings from the CAD lines in the dedicated CAD backcloth and generate a batter intercept string for the tee box.
Select Points --> Generate --> From Rectangles and the following dialog will appear. With the Pick Mode set to Element, set the Point Code to TB, Datum Height to 84m and maximum spacing to 5m.
Creating Features from CAD
Note: when creating designs it's good practice to densify strings as this will create well-shaped triangles and also allow better fitting of batter strings. We should avoid long thin triangles and if we only used the corner points we would miss ground detail between these points.
Since the level was set to 84m, all the points related will be at this level value. We now need to drop points at the top by 10cm to create a fall. The best way to do this is to drop the two top corner point levels, using Query Point (mini editor) and then grade the levels between these two points.
Grading Top of Bank String
The next step is to generate the batter intercept string. As indicated early, one of the BH symbols indicates the prefered position of the batter. By measuring from the nearest TB corner point to this BH point we get a slope of 1 in 3.5.
Next, we go to Design-->Strings Batter-->All and fill out the dialog box, seen below. We could batter up and down but only need Down. This slope is set to 3.5. Our LiDAR file sk4917_DSM_1M is used as a Reference DTM to stop the batter and use a String Code of BB. Since we don’t want to see sharp corners, we will also set the Fan Angle to 15 degs.
Setting the Batter String Parameters
You will notice batter points appearing opposite the same points on the top of the bank or seeding string. In simple terms n4ce takes a perpendicular section at each seeding point then calculates the intersection from where the batter string cuts the reference surface. This can be up, down or both. In our case, we chose down at 1 in 3.5 so it passes close to the reference point.
You will also notice the rounded corners, which are called Fans. In the above example, this was set to 15deg. A DTM was then formed using the top and the batter intercept strings.
The maximum height differences at the eastern (left) end of the tee box from the upper surface teeing surface to the existing ground are between 0.9m and 1.24m.
Note: the BH point symbols representing the approximate positions of the proposed tee box and pitching area are set to NO model so will not be included in the DTM.
This DTM was then used in Volumes by Strings calculations to give the overall quantity of material in the raised tee box, which approximated 300 cubic metres. The footprint areas of cut and fill were also calculated. CSV files can be created from these strings for setting out if required.
Note: the string volumes method uses the batter intercept string to isolate all the triangles within the model. A best-fit plane through this string is used to represent the reference surface.
An alternative option would be to create a separate model of the batter string and project the tee model down to this reference surface. The string method is quicker and produces very similar results. The lesson here, use appropriate tools!
Volume of Proposed Tee Box Using Strings
Ten 3m driving bays were proposed together with the 2m walkway, as shown below. Whilst 1.5m square artificial mats would be supplied, it was felt that space should be made so golfers could drive off the grass, ahead of these driving mats. The bay demarcation, driving mats and annotation shown here was drawn using CAD tools found in the dedicated CAD backcloth.
The layout of Driving Bays
Since CAD is not carried through into the 3D viewer, the CAD layout was transferred into a model, using the Points --> Generate from lines. These points were then inserted into the DTM using DTM --> Edit --> Apex Include. Doing this by List is the easiest option here, but you may have to do a little editing to switch or honour break lines.
Next, we used groups to identify different zones within the model, as shown below. These groups can be found in the project file and are called Banking, Mat, Tee Top and Walkway. You will notice when going into the groups icon that groups can be locked to prevent overwriting.
The proposed chipping green was designed to be used by several golfers at the same time, testing both bunker shots and chipping. A little artistic licence was used to create a chipping area with some character as it's likely that this will finally be shaped during construction.
Firstly, we digitised a string called EB, passing through the chipping green stake points, taking levels from the sk4917_DSM_1m model.
Inserting Base Outline of Chipping Green
This string was then closed and curve fitted. Next, we densified the EB string to 1m spacing, also dropping levels onto sk4917_DSM_1m. The 1m spacing will help when adding further detail, like bunkers.
Densifying Base String
We’re now in a position to create a batter string to form the putting surface. We wish to make the putting surface horizontal, and at a level where golfers can both chip up and down onto its surface. We, therefore, chose a level of 82.5, which is close to the existing ground at the southern end, as shown above. We now need to batter both up and down inside the baseline defined above.
Note: Ideally there should be a slope of the chipping green to remove any surface water. We’ve modified the surface here using a sloping Trend, with 50mm fall right to left.
Using Design-->Batter All with Up & Down at a Grade of 3.5 to a Reference Datum of 82.5 with codes of TB and BB. You will notice that there is an option to Remove Cusps This is where the projected batter point overlaps with its adjacency creating a cusp, and will remove them for you. Otherwise, you would have to remove these manually by deleting points.
Creating Batter Strings
We’re now in a position to form the DTM. If this was all we needed then the job would be close to being finished, but we need to add bunkers. These encroach into the side slops of the pitching green and can be sketched out, inserting points with levels taken from this DTM.
Moving External Levels to sk4917_DSM_1m
Since some of the inserted points have fallen outside of the chipping green model, these will have a null level. The List select option is useful here. Adding points to the list allows you to work on just these points, like moving them to the sk4917_DSM_1m model.
We now need to include the bunker points in our model. Two options are available here. Firstly, stitching encapsulated points into the DTM using DTM-->Edit-->Apex Include but this will not include the external points, shown here Listed. You would have to stitch these external points into the model manually. The other option is to delete the DTM and recreate it, which is what we will do here; followed by some DTM editing and adding of groups.
The baseline passes through the bunkers, so points falling on this feature need to be removed from the DTM using Apex Remove. Groups are then added for Batters, Greens and Bunkers.
Editing DTM Followed by Adding Groups
To complete the picture, targets were created at 50yd intervals from the teeing area. Since all of the work carried out so far has been in metres and golfers are interested in yards, a conversion factor was needed. We used 1m = 1.09361yrds.
A two-point feature line was added from the far left tee box to the furthest point south in the practice ground. This is the extent of the driving distance and is approaching 250yds. The line was then densified at chainages of 45.720m, which represents 50yds intervals.
Chainages were then added to these points in Design-->Design Line-->Dimension Chainages, which adds a CHN= attribute to each point.
In the code table for this feature, a Text Macro was added Ch=%.2(CHN*1.09362)m. This gives a running distance along the feature and can be used to place circular targets. These were drawn in the dedicated CAD backcloth as circles and then converted to points, using Points-->Generate-->From Circles. A 1m spacing was used with levels taken from the sk4917_DSM_1M model.
Positioning the 50yd Targets
These targets were then modelled and then grouped with a solid colour. This then allows viewing of the models in 3D against the backdrop of the aerial photography for the whole site for impact studies.
Sections were also taken through both the proposed tee box and chipping green, showing height differences between the design and the existing ground.
Cross Section Through Tee and Green
A cross-section was taken through the proposed tee box and chipping green, as shown here with a 1.5x vertical magnification.
A long section was also taken through the proposed teeing box and the practice ground. A sight line 1.5m above the teeing box was added to show that there was a clear line of sight to the landing area for long drives.
Since many of the decision-makers at the golf club have a non-technical background, visuals were created and posted for members to make comments. The new designs were approved at a committee meeting and work has commenced putting these designs into practice.
The green staff have made some changes to the initial designs, going for a 15m wide teeing box and have shaped the chipping green differently. But, this was a useful exercise and shows how n4ce can be used for other projects. Final images to follow.
The project is being made available for you to experiment with different designs yourselves.
Update August 2020 – Point Cloud
Since the original design was submitted and approved by the club, earthworks have been completed and the chipping green finished. We took the limited access to the course, during the covid-19 lockdown, to complete an as-built survey of the new build and update parts of the course which were improved, including bunkers, greens and tee boxes.
Carrying out GNNS Update Survey on 5th Hole New Tee Box
Model Of Update Survey
A combination of GNNS and a Drone survey was carried out on the practice ground, including the new teeing box and chipping green.
New Teeing Box and Chipping Green – As-Built
Here we are showing the new build against that backdrop of the aerial photography and LiDAR grid and NOT the point cloud, hence the spikes where the trees are.
As-Built Teeing Box and Chipping Green
Control points were identified for a Drone survey. These were located during the GNNS survey and identified with BH symbols in the above image covered the length of the practice ground. The Drone survey resulted in a point cloud, which is shown below.
Point Cloud Created from a Drone Survey
The weather was not ideal, being very windy but the drone compensated well. We flew at a height of 40m to avoid trees, along pre-prepared flight paths. In hindsight, this was too high as it reduced the resolution of the cloud.
The control points were digitised into n4ce and the control coordinates added to a Co-ordinates folder. This makes it easier to apply the transformation, but you must match the point numbers and codes. Also, add these points to the List.
Applying a Transformation to Digitised Points
GNNS Control Points
When applying the transformation you will be asked to accept the Listed points, then select the Load option followed by the Co-ordinate folder containing the control coordinates.
Selecting Control Points For the Transformation
This transformation must be saved so that it can be applied to the point cloud. We are plan to combine the GNNS and point cloud survey so the coordinate systems must be the same!
Merged GNNS Model and Point Cloud
The point cloud transformation can be found in the Point Cloud Tools tab. You will be invited to select the appropriate transformation. The GNNS model can then be added to the backcloth and seen in the 3D viewer, as shown above.
Just one more feature to look at. You can set the viewing priorities in the Properties panel so that the model appears first. Here we have set the Tee Box and Chipping Green to Always Visible.
Further options in the 3D viewer can be investigated, including a fly-through.
Comparing As-Built against Design
Since the original designs were carried out for approval, rather than strict build dimensions, the green staff used their creative licence during the build. But we are still interested to compare the original design against the as-built. This is quite easy to do in n4ce, using the backcloth facility. Query options can be used in the plan view to show distances, levels difference and areas between the two sets of models.
Comparing As-Built against Design
A section was taken through the LiDAR data, As-Built survey and the Design. In the quick viewer, you can interrogate height differences and clearly see the offsets. The blue line in the section represents the as-built profile.
Whilst the finished level of the chipping green is close to the design, the tooltip alongside the cursor is showing the tee box is approx. 0.4m above the design. This will favour sightlines by golfers using the higher surface. (see earlier Long section)
Comparing As-Built Against Design in 3D
Further query tools are available in the 3D viewer.