Spot Elevations are the foundation of basic topographic surveying. This traditional surveying technique has been around for years and is a tried-and-true method, but it takes a lot of time to accomplish. What if there was a faster and more efficient way of creating Spot Elevations? By combining drone photogrammetry with Virtual Surveyor, you can accomplish in hours what would normally take days. You can revolutionize the way you survey spot elevations by some forward thinking and some adaptation to the emerging technology.
- Starting Your Spot Elevation Project
- Traditional Spot Elevations in a Digital World
- Revolutionize the Spot Elevation Process
- Clean Up Points on the Elevation Terrain
- Annotate the Z Elevation of Points
- Export the CSV with Point Information
Starting Your Spot Elevation Project
A project has come up for a construction site and they need you to survey a large area of the site. Rather than putting your hiking boots on and shouldering the ol' GPS rod, you've been given a Digital Surface Model (DSM) along with a photogrammetric orthomosaic of the job site from a drone that had flown over the entire ~1,100 acre area. In case you're wondering, it probably took the drone less than two hours to fly all 1,100 acres! If you wanted to compete with that in a more traditional sense, you might be able to hire a team of Olympic speed walkers with GPS enhanced shoes to mark points for you, but personally I'd just pick the drone.
The DSM you've received is a 2-dimensional GeoTIFF file that includes X, Y, and Z coordinate data information. It looks like a grayscale blob, except it is packed with necessary spatial information.
Load the DSM
When you load the DSM into Virtual Surveyor, the software converts that data into an interactive 3D Elevation Terrain item that is essential for everything you do in Virtual Surveyor.
Like a detailed sci-fi hologram for surveyors, with just your computer mouse and a monitor you can pan, scale, zoom, and inspect every facet of the 3-dimensional terrain with omniscient proficiency... A geographic god over your own little section of earth.
Load the Orthomosaic
The orthomosaic is hundreds or thousands of orthophotos that were geo-rectified and run through a software that interprets and compiles all the orthophotos into one orthomosaic. It's probably the closest thing we currently have to giving you eagle eye clarity. When you import an orthomosaic into Virtual Surveyor, it is converted to an Image Terrain.
Since each of the orthophotos are geo-rectified and combined into one, you have a seamless aerial color image of your survey site with extensive detail. Depending on the camera you use on your drone, you might be able to see crazy levels of detail for every tree or bush, even down to every twig or blade of grass on your site.
Creating Your 3D Virtual Environment
Once you drag and drop (or upload) both the DSM and the orthomosaic files into Virtual Surveyor, the DSM is quickly and automatically converted to a 3D Elevation Terrain item. The Image Terrain perfectly wraps over the Elevation Terrain, giving you the foundation to start your work and create Spot Elevations on a virtual copy of your job site.
We're pretty eager to show you how cool it is to create your spot elevations in Virtual Surveyor. It allows you to save time and money by getting paid the same for less time spent on the project. Plus, you don't have to go tromping through the weeds for hours on a sweltering day (or a freezing one) unless you really want to! So without further ado, let's shoot some spot elevations!
Traditional Spot Elevations in a Digital World
Let's jump right in. You have Virtual Surveyor open with your recently created Elevation Terrain (from the DSM) and Image Terrain (from the Orthomosaic) loaded into the program, giving you a complete Virtual Environment that you can interact with in the Viewport.
Looking at your site, you need to analyze how you'll survey it in a digital environment. After some thought, you'll likely realize (as we did) that the best way to survey the area digitally is the same as you would in person, with points (spot elevations) representing an XYZ at a specific location. You treat it the same as if you had to walk along and plot points with a GPS or rover. Lets pick a corner of the site as a starting point for our traverses and begin creating points in a grid pattern of about 50 feet apart.
Manually Create Spot Elevations
From the HOME tab, enable the Point tool and simply start left-clicking on your digital environment to create points as if you were walking on the ground yourself and clicking on capture with your rover. Like the pattern of mowing the lawn, once you get to the end you move over 50 feet and start heading back, taking more points at around 50 feet apart. You are probably getting a good feel for how much easier and faster this is; instead of walking that whole distance, you were able to virtually traverse it and place your shots with simple clicks.
You may be asking yourself, "well this is great, but where are my Z elevations?". Select any point you have created (via the Project View or in the Viewport) and look to the Selection box. You'll notice it lists X, Y, and Z coordinates! Your X, Y, Z coordinates are automatically extracted from the Elevation Terrain. The Point tool always places points directly on the terrain with the appropriate X, Y, and Z elevation values.
If you were feeling particularly keen, you may have also noticed that the points are not only created on the terrain, but also in the LAYERS tab under No Layer. This area that lists out created project items is called the Project View.
You might be thinking "Hold up! How do you know we're getting the points every 50 feet apart?", the fact is that right now, we don't; we're just eyeballing it. If this seems a bit unorthodox and unprofessional, you'd be right. We can do way better, and we'll show you how! But hopefully you're getting the gist of how to navigate the terrain at this point.
Now let's tidy up how the points are created, both on the terrain itself and in the Project View, and get some accurate measurements that make it a bit easier for you to create a precise grid and speed up the process. But first, we'll need to remove the points we just created so that we have a clean slate to make some new and more accurate measurements.
You can enable the Erase or Area Select tools to remove the points, or just disable the Point tool, then hold shift + left-click and drag the curser to create a box around the points you want to highlight (you can also use the Project View to select all the points at once and delete them from there). Once all the points are highlighted, simply press the Delete key on your keyboard to remove them.
To create a more organized grid of points, we'll use the Graticule Lens. The Graticule Lens is part of our Analysis tools that provide ways to measure your site, which includes unique tools called Terrain Lenses that let you visualize your site in multiple ways. Simply click on the ANALYSIS tab, look in the Terrain Lenses section, and set the interval spacing for the Graticule terrain lens to 50 ft. Then click the Graticule button to show the lens on the Elevation Terrain.
Almost like magic a grid appears! While the area is huge and will take some time to manually add points, it is still lightyears faster than having to walk the entire site.
You can now place points in 50 ft increments on a perfect grid, by left-clicking each square corner of the Graticule Lens.
You can continue to manually create your spot elevations (our FREE Valley version encourages that for small sites), but if you're wondering whether there is an even better way to create spot elevations, there is! Now that you have a basic understanding of the digital surveying process, let's show you how we revolutionize the creation of spot elevations by combining human intelligence with the efficient capability of a computer.
Revolutionize the Spot Elevation Process
Create a Boundary
Let's start at the part of the project right after you created the Elevation Terrain and Image Terrain. We know, this is nearly starting over from the very beginning, but stick with us, we promise it will pay off!
At this point, you need to define the site's boundary where you want to create your Spot Elevations. Thanks to a nice image from the drone, digitizing the boundary extents is very easy to trace. To define an area, you can use a drawing tool for creating boundaries. To use this drawing tool, click on the HOME tab, go to the Drawing section, and enable the Boundary tool.
Using your mouse, left-click around the area you want to focus and start drawing your boundary line. Continue drawing until you have created a perimeter around the survey area and right-click to finish or "close" the boundary.
Your boundary is now created and you can move on to organizing and creating your layers in the Project View.
Organize Layers and Items in the Project View
With the boundary created, you can organize your project items in the Project View to help with the efficiency of managing your terrain items. You'll quickly see why this is beneficial to organize your items and information. Just like having an organized workstation, if you need to make edits or changes you'll be glad you know where everything is and you don't need to spend extra time looking for what you need. Not that there is anything wrong with ol' uncle Larry's disheveled shed full of museum antiquities, but we're trying to make some money here.
In the Project View under No Layer, you should see your Elevation and Image Terrain files, along with the newly created boundary. Create a new layer by right-clicking in the light grey area anywhere under layers to get the option to create a new layer. We'll go ahead and create a new layer called "Spot Elevations" as an example to organize project items. You can make multiple layers like this and separate them as your points and boundary layers, or combine them and put both the Boundary and Points in the same layer like we are in this example. Whatever helps you organize your content the best. The bigger the project, the easier it is to manage with multiple properly named layers.
With the new layer available, you can right-click on the Boundary item to Move Selection to Layer, then just pick the Spot Elevations layer and your boundary will be moved to that layer so it's easy to find later. If you find it helpful, you can always create a new layer, rename it to Elevation Terrains, and move your Elevation Terrain and Image Terrain items into that layer. By default, the No Layer is always there and cannot be renamed.
As something of note, notice that the Spot Elevations layer is in bold lettering. This just means it is your "active" layer, and that any new project items you place on the terrain (e.g., Points) will appear in that layer. You can set any layer as "Active" by right-clicking on the layer in the Project View and selecting Set as Active Layer.
It may seem tedious and long winded to explain all the layer organization to you, but we promise all this will be second nature to you in a very short amount of time. It will only take you seconds to set up your layers at the beginning of your project, and you'll likely change names and shift content around as you see fit as you get to know the system more. It saves massive amounts of time once you start working with all the project items. Plus, once the data is exported to a CAD format, the layer information carries over. E.g., if you have layers such as Topo and Pavement, they will be created in CAD as well, along with the descriptors. This way, you can use the same Layer/Descriptors you would normally use on your GPS or total station unit, and the data all looks the same as if it was collected in the field.
Create an Entire Spot Elevation with Just a Few Clicks
Now for the best part of all this; creating Spot Elevations with an automated function! It's fast, it's slick, and if you've ever marched over dirt, mud, and brush all day carrying a GPS rod, you'll appreciate it more than most. Even if you haven't done that, this function is simply awesome! And, when the work is done for the day, you still get to enjoy a cold beer... without all the aching joints.
Remember that Boundary you created? Select the boundary so it highlights in both the Project View (highlights as an ochre color) and the Viewport (vibrant green halo).
We're going to place points in the focused area of that boundary. Go to the HOME tab and look in the Point Grid section.
Leave the Type as Rectangular as that will give you the same rectangular pattern we were going for initially. There are a few options for the Type of grid patterns that you can choose from, but for this map it's probably best to use the most common one: Rectangular. A Rectangular pattern type essentially creates transects across a field that you would normally walk.
For the Grid Size, what kind of spacing would you normally do between points? Most surveyors use 50 or 100 ft. between points. In a virtual environment, we'll change the Grid Size to 25 ft. That's right, 25 ft! A good rule of thumb is you can measure by half of what you'd normally collect in the field. This gives you a better model without overwhelming yourself with data. You'll find your own sweet spot for point measurements on each project you do, but for this project just trust us and see how it turns out. Click the Point Grid button and watch the magic happen.
Now all the points are created, and you have your Spot Elevations.
All that is left is to clean up a few points to make sure they have not been placed on machinery, vegetation, or any other obstacles on the terrain that could interfere with a detailed Spot Elevation model.
Clean Up Points on the Elevation Terrain
To Clean Up Points simply means to remove or move them from objects on the Elevation Terrain that interferes with our spot elevations.
After inspecting the terrain, you'll notice that a there is a portion in the southeast area that has a lot of machinery and worksite equipment. A number of points have landed on objects in that area after creating the point grid. We'll need to remove or move points from the objects to make sure we have an accurate ground measurement.
To remove points, ensure you're on the HOME tab and click on the Erase button to enable it. You'll notice your mouse curser changes to the Erase icon when hovering over the Viewport.
You can move around the terrain and change view angles in order to best see where points landed and remove them from objects on the terrain. In the example below, we use a top-down view to remove points from the trucks, machinery, and any other objects on the terrain.
Annotate the Z Elevation of Points
For extra brownie points when you turn in your spot elevation, we have a function in Virtual Surveyor that can bring a lot of value to your spot elevation image. You can show the Z height of each point by showing the annotation of each point on the Viewport. This will only show up in Virtual Surveyor and can be exported as images to include with your final product.
To annotate your point grid, select your Grid Points in the Project View and go to the TOOLS tab. In the Annotate section, tick the Z check box.
You can see the Z elevation data portrayed on every Grid Point in the Viewport.
If you'd like to include these images when you turn in your project, go to the EXPORT tab to save the Viewport screen as a JPEG image. Once in the EXPORT tab, click the Copy Viewport down arrow, and Save Viewport as Image.
Export the CSV with Point Information
Once you are done creating your survey, you can take your Spot Elevations and export them as a .csv file to finish the job and hand off your data to the engineer or construction contractor. Go to the Export tab and In the Survey section, change the Format to a .csv file and click Export Survey.
Save the file with an appropriate name and file location (we'll use Spot Elevations for this file name as an example).
Open your Excel file to verify the information.
If you saved images of the annotated points from the Viewport, don't forget to include them with your .csv file when you submit them to your project overlords. And that's it, you're done!