Visualize bathymetry in 2D
The basis of terrain mapping is often a digital elevation model (DEM). This is raster data where each pixel represents an elevation above or below sea level. You'll start with a DEM of Norfolk Canyon and create some derivative products from it to depict the terrain in different ways. You'll also make some measurements of the canyon to include in your report.
Create a hillshade
A common way to depict terrain, both on land and underwater, is with hillshading. You'll begin your exploration of Norfolk Canyon by creating a hillshade. This will provide a more naturalistic depiction of the bathymetry.
- Download the Visualize Bathymetry .zip file and unzip it to a location on your computer, for example, your C drive.
- Open the unzipped VisualizeBathymetry folder and double-click VisualizeBathymetry.aprx to open the project in ArcGIS Pro.
- If prompted, sign in to your ArcGIS account.
If you don't have ArcGIS Pro or an ArcGIS account, you can sign up for an ArcGIS free trial.
A map appears, containing a DEM, covering a part of the continental shelf east of Virginia. Shallow areas are shown in white and deep areas are shown in black.
The data for this map comes from National Centers for Environmental Information (NCEI), a branch of The National Oceanic and Atmospheric Administration (NOAA). You can read about the original dataset at U.S. Coastal Relief Model Vol.2 – Southeast Atlantic and about how it was modified on its item page.
This data is also explored in the lesson Find ocean bathymetry data.
DEM data can be used to create a variety of visualizations that represent different aspects of the seafloor. You'll start by creating a hillshade.
- On the ribbon, click the Analysis tab. In the Raster group, click Raster Functions.
The Raster Functions pane appears. Raster functions are a faster and more lightweight alternative to geoprocessing raster tools.
- Scroll to the bottom of the Raster Functions pane and expand the Surface group. Click Hillshade.
Hillshade is a cartographic technique that mimics how sunlight illuminates some hillsides while casting others in shadow. This gives landscapes a three-dimensional appearance similar to how they might appear from an airplane. While the seafloor does not receive enough sunlight for the same effect to be visible in the real world, it is still a useful visualization technique to help depict bathymetry on maps.
- In the Raster Functions pane, for Raster, choose Atlantic_DEM.tif.
- Accept all of the defaults for the remaining parameters and click Create new layer.
A new layer appears on the map. Now the continental slope and its canyons appear three dimensional.
This layer is a view, not a new dataset. It references the data in the Atlantic_DEM.tif layer. Raster functions create in-memory views instead of duplicating data.
- On the ribbon, click the Map tab. In the Navigate group, click Bookmarks and click the Norfolk Canyon bookmark.
The map zooms to the canyon.
- In the Contents pane, uncheck the box next to Hillshade_Atlantic_DEM.tif to turn the layer off.
- Turn the hillshade layer back on.
The hillshade makes it easier to see the canyon walls and its floor.
Create contour and slope maps
Hillshading is not the only way to visualize terrain on maps. Different visualizations can offer different forms of insight. Next, you'll make contour lines and a slope map for your study area and use them to become better acquainted with Norfolk Canyon.
- Open the Raster Functions pane. In the Surface group, click Contour.
Contour lines are another cartographic method for depicting terrain. They are isolines that represent areas of equal elevation. When contour lines are closer together, the change in elevation is steep. When they are far apart, the change is gradual.
- For Raster, choose Atlantic_DEM.tif. Leave all the other parameters set to their defaults.
- Click Create new layer.
Contour lines appear on the map.
Question 1: How would you describe the pattern shown by the contour lines? What it can tell you about this area of the ocean?
Answers are provided at the end of the lesson.
The contour lines provide an indication of slope, but you can depict the steepness of terrain more directly with the Slope raster function.
- In the Raster Functions pane, in the Surface group, click Slope.
- For DEM, choose Atlantic_DEM.tif. Leave the other parameters set to their defaults.
- Click Create new layer.
The slope layer shows flat areas in black and steep areas in white.
The steep areas are hard to see, so you'll change the color scheme.
- Close the Raster Functions pane.
- In the Contents pane, under Slope_Atlantic_DEM.tif, right-click the color scheme.
- Click the color scheme menu and choose Cyan to Purple. (Point to color schemes to read their names.)
The map changes. The steepest areas have the darkest blue color.
Question 2: What are the steepest areas in your study area?
Measure the canyon
Next, you'll make some measurements of the canyon. You'll measure the width of the canyon from rim to rim and the width of the canyon's floor.
- Zoom to the Measure bookmark.
The map zooms to a stretch of the canyon on the continental slope that is relatively straight.
Light blue areas represent flat terrain. The thick curving light blue line in the middle is the canyon floor, while the thin light blue lines on either side represent the rims of the canyon.
- In the Contents pane, drag the Hillshade_Atlantic_DEM.tif layer above the Slope_Atlantic_DEM.tif layer.
- Turn the hillshade layer on and off to compare it to the slope layer.
- Once you feel confident that you understand where the canyon floor and rims are, turn the hillshade layer off.
- If necessary, zoom back to the Measure bookmark.
- On the ribbon, click the Map tab. In the Inquiry group, click the bottom half of the Measure tool and click Measure Distance.
- In the Measure Distance window, ensure the first menu is set to Geodesic and the second menu is set to Meters.
Geodesic measurements take into account the curvature of the earth.
- Click the north rim of the canyon, along its straight stretch. Double-click the south rim to measure the distance across the canyon.
The width of the canyon is reported in the Measure Distance window, under Sum. The width in this area ranges from 3,000 to 3,700 meters.
- In the Measure Distance window, click the Clear Results button.
- Measure the width of the canyon floor in the same area.
Question 3: How wide is the floor of Norfolk Canyon?
- Close the Measure Distance window.
- On the ribbon, click the Map tab. In the Navigate group, click the bottom half of the Explore tool. Click Selected in Contents.
The explore tool normally displays a pop-up for the topmost visible layer. Now it will show a pop-up for any layer that you choose.
- In the Contents pane, select the Atlantic_DEM.tif layer.
- On the map, click the north rim of the canyon.
Stretch.Pixel Value reports a value between -1,200 and -1,100. Since this layer is a DEM, this value represents elevation. However, you don't know yet what unit the elevation value is reported in. You will find out in the layer properties window.
- In the Contents pane, right-click Atlantic_DEM.tif and click Properties.
- In the Layer Properties window, click the Source tab. If necessary, expand the Data Source section.
The Vertical Units value is listed as meters.
- Close the Layer Properties window.
The pop-up indicates the rim of the canyon in this area is more than 1,100 meters below sea level.
- Find the elevation of the canyon floor.
Question 4: What is the elevation change (vertical relief) between the canyon's rim and floor in this area?
The steep walls and varied depths of ocean canyons create a varied physical landscape, and many habitat types are condensed into a relatively small area. This, and other factors, promote a high diversity of ocean life and make canyons, including Norfolk Canyon, biological hot spots.
- Close the pop-up. On the Quick Access Toolbar, click the Save button.
You have visualized the bathymetry of Norfolk Canyon with several techniques and gathered some measurements.
Visualize bathymetry in 3D
Norfolk Canyon is a biodiversity hotspot, supporting a much greater abundance and diversity of life than the surrounding area. It is home to deep-sea corals, sponges, crabs, anemones, and many kinds of fish. The canyon serves as a natural passageway from the shallow waters of the continental shelf to the deep waters of the abyss, so migrating wildlife, ocean currents, and organic matter are all funneled through this relatively narrow part of the sea. The canyon, with its steep rocky sides, soft bottom, and varied depths, also promotes biodiversity by providing a wide range of habitat types condensed into a relatively small area.
Read more about canyon ecosystems at Mid-Atlantic Deepwater Canyons.
Photos and videos of ocean canyons can only capture small areas at once. There is not enough light underwater to see the entire canyon. Next, you'll create a 3D visualization and animation that can show the entire canyon and demonstrate the terrain responsible for an important ocean ecosystem.
Visualize Norfolk Canyon in 3D
First, you'll convert your 2D map to a 3D scene. You'll adjust the elevation surface and the vertical exaggeration to best show Norfolk Canyon.
- On the ribbon, click the View tab. In the View group, click Convert and choose To Global Scene.
A new view appears, named Map_3D. 3D maps are referred to as scenes.
- In the Contents pane, turn off all layers except Hillshade_Atlantic_DEM.tif, World Ocean Base, and WorldElevation3D/Terrin3D.
- Pan and zoom to explore the scene.
- In the bottom of the scene view, click the Show full control button to expand the scene controller. Drag the circle in the middle of the control to tilt the scene.
Alternatively, use the middle button on your mouse to tilt the scene. Learn more about navigating 3D scenes at Navigation in 3D.
While the scene can be explored in three dimensions, the data does not yet appear 3D.
- In the Contents pane, press the Ctrl key while clicking one of the arrows next to any of the layers.
All the layers collapse, making it easier to read the Contents pane.
Scenes have three layer categories in the Contents pane: 3D layers, 2D Layers, and Elevation Surfaces. All of the layers from the 2D map are listed in the 2D Layers category. These layers draw draped over the ground surface of the map. This is similar to how a film shown through a projector will drape over three-dimensional surfaces.
You'll zoom to another part of the world to better observe this.
- Zoom to the Aleutian Islands bookmark.
- Pan, zoom, and tilt the map to explore the islands.
The land areas are three dimensional, rising above the sea, but the ocean areas are flat. Any appearance of depth comes from the colors and textures of the basemap.
In the Elevation Surfaces layer category, the Ground elevation surface determines the topography shown in the scene. The existing ground layer, WorldElevation3D/Terrain3D, is a global layer provided by Esri, intended for mapping land areas. It depicts the ocean as flat, so it's not suitable for studying bathymetry. However, you have other elevation data in your project that can replace it.
- In the Contents pane, right-click Atlantic_DEM.tif and click Zoom To Layer.
- In the Contents pane, drag the Atlantic_DEM.tif layer into the Elevation Surfaces layer category. Place it under Ground and above WorldElevation3D/Terrain3D.
Now the DEM provides the elevation values necessary to map your study area in 3D. All of the layers in the 2D Layers category are draped over the DEM instead of the default surface. They appear to be cut out of the flat ocean surface.
- Pan, zoom, and tilt to explore the scene.
Sometimes, especially when viewing very large areas, 3D visualizations benefit from some exaggeration.
- In the Contents pane, under Elevation Surfaces, click Ground.
- On the ribbon, click the Appearance tab. In the Drawing group, change Vertical Exaggeration to 3.00.
The canyons of the continental slope appear more dramatic. Similar to the hillshade effect, vertical exaggeration can make terrain easier to interpret.
- Explore Norfolk Canyon with the exaggerated terrain.
Learn more about visualizing terrain in 3D scenes in Work with elevation surfaces.
Explore with elevation profiles
Previously, you measured the width and elevation change of the canyon. Next, you'll visualize and further explore those measurements with an elevation profile chart.
- Zoom to the Measure bookmark.
- On the ribbon, click the Analysis tab. In the Workflows group, click Exploratory 3D Analysis and choose Elevation Profile.
- On the map, draw a line across the canyon, stretching from rim to rim. Double-click to complete the line.
The Elevation Profile window appears, charting the change in elevation between the two points.
- Press the C key to navigate. Pan and tilt the scene to view the elevation line on an angle.
- Point to the graph.
Elevation values for the specific location appear on the graph, and the corresponding location is highlighted on the scene.
- On the map, drag the handles of the line to measure along the floor of the canyon.
- Adjust the handles to view elevation profiles for other parts of the canyon.
Question 5: How does the depth of Norfolk Canyon vary from east to west?
- Close the Elevation Profile window and the Exploratory Analysis pane.
Change the color of the scene
You'll create a 3D animation of Norfolk Canyon to share with others. First, you'll change its color to blue to provide a visual cue that the landscape is underwater.
- In the Contents pane, turn off the World Ocean Base layer. Turn on the Slope_Atlantic_DEM.tif layer.
- Drag the slope layer above the hillshade layer.
You'll use the slope layer to color the scene.
- Ensure that the Slope_Atlantic_DEM.tif layer is selected. On the ribbon, click the Appearance tab. In the Effects group, for Layer Blend, choose Soft Light.
The colors of the slope layer are now blended into the hillshade. You'll change the color scheme to one that is more blue and less green.
- In the Contents pane, expand the Slope_Atlantic_DEM.tif layer and right-click its color scheme. Click the color scheme menu and check Show all.
- Scroll to the bottom of the color scheme list. Scroll up a short distance and click the Yellow-Green-Blue (Continuous) color scheme.
- Right-click the color scheme again and click the Reverse color scheme button. Click outside of the color scheme window to commit the change.
The new color scheme gives the scene a deep underwater appearance.
Create a 3D animation of Norfolk Canyon
It can be difficult to visualize the 3D ocean floor clearly in a single image. Animations allow you to show an area from multiple perspectives and give a fuller picture of its shape. Next, you'll create a fly-through animation of Norfolk Canyon and export it as a video. The video below is an example created with the following steps.
- On the ribbon, click the View tab. In the Animation group, click Add.
The Animation Timeline pane appears below the map.
- Zoom out so you can see the entire Hillshade_Atlantic DEM layer.
This will be the opening shot of your video.
- In the Animation Timeline pane, click Create first keyframe.
A new keyframe appears under Keyframe Gallery, with a thumbnail image of the opening shot.
- Zoom, pan, and tilt the scene until the view is from inside the canyon, close to its eastern end.
- In the Animation Timeline pane, click the Append next keyframe button.
- Travel up the canyon toward the mouth, capturing keyframes as you go. Create no more than ten keyframes.
- Zoom out to show the entire canyon and capture the last keyframe.
Next, you'll set the length of the entire video to 30 seconds.
- On the ribbon, click the Animation tab. In the Playback group, change Duration to 00:30.000.
- Click the Play button to preview the animation.
The terrain may appear to shift as the animation plays, but this effect will not be present in the final exported video.
Next, you'll edit your animation by repositioning one of the keyframes.
- Under Keyframe Gallery, double-click one of the keyframes.
The scene zooms to the keyframe's position. The keyframe should appear highlighted, indicating that it is selected.
- Pan, zoom, and tilt the scene to change its view. In the Animation Timeline pane, click Update.
- On the timeline toolbar, click the Return playback to the beginning of the animation button and then click Play to preview the changes to your animation.
- Update more keyframes as necessary.
When you are happy with the animation, you'll export it as a video.
- On the ribbon, on the Animation tab, in the Export group, click the Export Movie button.
- In the Export Movie pane, for Movie Export Presets, choose Draft.
- For File Name, click the Browse button. In the Animation File Location window, under Project, expand Folders and choose VisualizeBathymetry.
This is the folder that you unzipped at the start of the lesson.
- For Name, type Norfolk_Canyon. Click All files and choose MPEG4 (*.mp4). Click Save.
- In the Export Movie pane, accept all other default settings.
- Click Export. When the export is complete, click the Play the video link.
Optionally, export the video with the HD720 or GIF presets, for a higher quality output. Exporting the video with these presets may take a long time. You can continue to use ArcGIS Pro for other tasks, but do not close the Export Movie pane or ArcGIS Pro.
- On the Quick Access Toolbar, click the Save button.
In this lesson, you learned techniques for visualizing bathymetry in 2D maps and 3D scenes. You learned how to create hillshades, contour lines, slope maps, and animations from a DEMs and how to measure distances and elevations on terrain. You also learned about ocean canyons and Norfolk Canyon in particular. You can learn more about ocean canyons, and view maps similar to the ones you made in this lesson, in this story: Large Submarine Canyons of the United States Outer Continental Shelf.
- How would you describe the pattern shown by the contour lines? What it can tell you about this area of the ocean?
Almost all lines are crowded along the continental slope and to the east of the slope. This indicates that the continental shelf is very flat and that the continental slope is very steep, forming a dramatic transition zone between two areas of ocean.
- What are the steepest areas in your study area?
The steepest areas are along the sides of Norfolk Canyon and other canyons to the north.
- How wide is the floor of Norfolk Canyon?
The canyon floor ranges in width between 200 and 400 meters.
- What is the elevation change (vertical relief) between the canyon's rim and floor in this area?
The elevation change between the canyon's rim and floor is between 350 and 430 meters. Click the flat floor area of the canyon and observe the Stretch.Pixel Value in the pop-up. Subtract the rim depth from the floor depth to find the difference.
- How does the depth of Norfolk Canyon vary from east to west?
The canyon's floor transitions from shallow in the west (350 meters below sea level) to deep in the east (2,550 meters below sea level). This transition is gradual and smooth along the floor.