Using Photo Ephemeris Web, Part 9: Maps and Terrain in the 3D Celestial Sphere

WEB

This tutorial applies to Photo Ephemeris Web. If you haven't already read Part 7, please do that first - it covers the basics of how the 3D Celestial Sphere works.

Video Walkthrough

This 10-minute video gives you a walkthrough of the new functionality. For detailed coverage, please read on below!

Tutorial

As of v2.5 (April 2021), you can now display a map in the Celestial Sphere:

This feature is available for all users. And even better, for PRO subscribers, you can enable 3D terrain:

Note: 3D Terrain requires a PRO subscription

Compatibility: your browser and computer must support both WebGL and ResizeObserver to use this functionality. Both are widely supported today, but older browsers may not work.

See 3D Sphere Compatibility, Performance and Data Usage for further information.

Controls

Maps are displayed by default, but you can turn them off if you prefer, or in order to reduce data and power consumption. 3D terrain is off by default, but you can turn it on whenever you like. Your settings will be saved with your account profile.

The Visual Search controls are now off by default, to create extra screen real estate for the maps and terrain, but you can enable them using the new control to the right, as shown.

Map Style and Zoom

You can change the map style using the drop down control at the top left, and vary the map zoom level using the buttons at the bottom right:

Lighting and Shadow Effects

The light of the sun and moon is varied as you adjust the date or time. Intensity, color temperature, and ambient lighting levels are used to simulate real world lighting. You'll see in the various example screenshots in this article that terrain casts shadows allowing you to visualize the fall of the light on the land.

In addition, a "ghost light" is switched on when the scene would otherwise by completely dark (i.e. after the end of astronomical twilight when the moon is either down or less than 10% illuminated):

This serves two purposes: 1) it provides just enough light to see where you are (but see below if you need more) and 2) it serves as a visual clue as to when the sky is completely dark and conditions are suitable for astrophotography.

Worklight

Drawing further inspiration from the theatre, there is a "worklight" button at the top right of the 3D Sphere. On dark moonless nights, you can switch this on to be able to see the full map even when no source of "natural light" is available:

The light is a night vision-style fluorescent green, so there's no mistaking it for simulated sun or moonlight. The "workers" (as we used to call the working light fixtures in my theatre days) turn off as you adjust the time-slider, so all you see is simulated natural light. When you stop adjusting the time, and release the slider button, the workers will switch on once again, if enabled.

Choosing a suitable Map Style

When it comes to choosing the right map style, you should ask yourself what your goal is. Is it to visually identify a landmark you know to ensure you have the right place? If so, a detailed street map or satellite map is probably best. It's also probably best to do these "get your bearings" activities on the Map page rather than with the Sphere.

If your goal is to understand how the light falls on the land (and let's face it, that's really the point of all this), then we'd suggest using a simple clean map style, such as a street map, black and white map or transport style.

Why? It comes down to color theory, visual clarity, and the realities of satellite imagery capture. Satellite maps can look great in certain locations, e.g. Moorea in French Polynesia:

But - and this is particularly true for areas with lots of forest cover or green vegetation - things become very murky indeed at either end of the day:

Contrast this with the same time and place viewed using the black and white TopPlusOpen (de) layer:

It's much easier to see the fall of the shadows: the contrast remains higher and the green vegetation doesn't suck in the orange light.

Note: The max zoom level for TopPlusOpen varies by area. Higher zoom levels are available in Germany than in the USA, for example (because the map provider is the Bundesamt für Kartographie und Geodäsie). So you may need an alternative map style - we suggest something like Outdoors or Landscape.

One further advantage of plain old street map styles is that they typically don't include the pre-baked hill-shading seen in most topographic maps, and they don't have the unavoidable shadows of satellite imagery. Even though satellite imagery is generally captured at times that attempt to minimize shadows, they cannot be entirely avoided.

Any map style that includes shadows or hill-shading is generally going to give you visual clues that conflict with the dynamic shadows shown in Photo Ephemeris - be aware!

Alignments

If you want to align the sun or moon with a mountain summit (e.g. the classic "Diamond Mt. Fuji" shot), then you can use the 3D terrain feature in conjunction with the azimuth/altitude projection line to find out an approximate shooting location.

Here's an example from Boulder, Colorado. Mount Sanitas is the closest high point to the north of town, in the foothills of the Rockies. Where would we need to be to have the setting sun align behind its summit this weekend?

As you drag the time slider, projection lines show where the tip of the shadow will fall in direct opposition to the sun (or moon). On Apr 25, we should be able to catch the sun dropping directly behind the summit of Mount Sanitas just before 7pm:

Of course, if you're looking for more shot options, you should use Visual Search, which works perfectly in conjunction with the sphere and 3D terrain.

A Note on Map Zoom vs Camera Position

One important distinction to understand: there's a fundamental difference between map zoom and the camera position (by which we mean the "virtual" 3D camera in the software, not your actual camera or planned shooting location) in the 3D Sphere page.

The Map Zoom level is analogous to the scale of the map. The camera position is the point from which you are viewing the map (are you looking up close or standing back?). Moving your eye (the camera) closer to the map does not add detail to it, but it may make the existing detail easier to see.

How much map is shown?

The Sphere displays only a finite area at any one time. How much physical terrain is represented depends on the chosen map zoom level. If you zoom in (increase map zoom level), you'll see a smaller area in more detail. If you zoom out, you'll see a larger area in less detail.

You can adjust the Zoom level in the sphere by using the +/- controls in the bottom right-hand corner of the map.

What if it's not enough terrain?

When using the 3D terrain feature, it's important to be aware that shadows are cast only by the area displayed in the sphere. If you're in the Himalayas and Everest falls just outside the bounds of the sphere, then no shadows from Everest will appear anywhere - it's up to you to set an appropriate zoom level so that the terrain that affects the fall of the light is included.

But how do you know? Some tips to help you determine if you need to zoom out:

1. Before using the Sphere, view the area using a topographic map style on the Map page to get a sense of how mountainous/hilly the surrounding area is.
2. If you're planning to shoot a particular landmark (or from a particular spot), use Geodetics to drop the secondary map pin on your subject (or shooting location). When you view the Sphere check that the pin lies within the displayed bounds.
3. Viewing the 3D Sphere, adjust the time of day to around sunrise or sunset (or check both). Look at the shadows and see where they fall relative to the red pin. Now decrease the map zoom level to bring more terrain into view. Did the shadows change around the red pin? If not, then your original zoom level is fine.

For example, imagine you want to shoot Mount Baker in Washington from Bellingham:

When you view this in the Sphere, it's clear that you may want to zoom out - the secondary pin lies outside the bounds:

Click to zoom out one level - that's better:

Move the camera

We encourage you to be bold in moving the camera - this isn't the time to sit in orbit looking at the entire sphere from afar. Try zooming in, and spinning and panning around to get the most advantageous view of the terrain. You can never get too far lost - the camera will always remain pointed towards the center of the model. Moving the camera around will ensure you have a good mental model of what is being displayed - if you stick in one place, it can be easy to misread what is shown.

As a reminder, here are the ways to control the camera:

• Rotate: Left click + drag
• Fly in/out: trackpad pinch gesture / mouse scroll wheel
• Pan: trackpad Shift-left click + drag / mouse right click + drag

In the Hall of the Mountain King

Occasionally, the primary (red) map may appear embedded in the Earth, as if reaching down to puncture the ceiling of some subterranean cavern. Here's an example in Mount Meru (you haven't seen the film? watch it!):

This example is slightly contrived, but it shows the point: the elevation of the red pin, and therefore its position in the 3D scene is based on the chose elevation service (in this case, the relatively low accuracy GTopo30, shown in the selection just above the map). As GTopo30 is a low resolution model, it typically misses the extremes of mountain peaks. In other cases, data artifacts may result in other DEM models have an incorrect or missing elevation for certain points.

The default model, SRTM3, is itself slightly off in this case:

Better, but still too low. In this example, switching to SRTM1 (requires PRO subscription) gives the best  result:

In the future, we may be able to sample the 3D Sphere Terrain model to place the pin, but for now, this situation may arise from time-to-time, so please be aware.

(Arguably, showing the disagreement between the sources isn't entirely a bad thing: it lays bare the accuracy limitations of the source data used which may help to manage expectations!)

Terrain Artifacts

You'll see from the elevation data attribution below that the terrain model combines multiple different data sources. As a result of the processing, and sometimes due to limitations in the technology used to capture the data experimentally, in some places you may see weird looking topography. Here are some examples so you know what to look out for.

On the southern shores of Moorea once again, the ocean surface shows bulges:

On the north side of Snæfellsnes in Iceland, you can see non-existent sea stacks towering out of the ocean and geometric artifacts along the shoreline:

And who knew that parts of the Shetland Isles apparently lie below sea level (see the shadows in the lower right quadrant of the screenshot)?

Bottomless pits (actually not bottomless, just clipped) near Manaslu in Nepal:

Typically, these artifacts are observed in the following types of locations: higher latitudes, coastlines, some very steep mountainous areas.

We're dependent on the available elevation data sources to address these artifacts. Hopefully, over time, some of these will be cleaned up and we can incorporate updated models into the app. For now, please remain aware that will you encounter this from time to time.

Elevation Data Attribution

Thanks to the following organizations for the digital elevation model data used in the app:

• ArcticDEM terrain data DEM(s) were created from DigitalGlobe, Inc., imagery and
  funded under National Science Foundation awards 1043681, 1559691, and 1542736;
• Australia terrain data © Commonwealth of Australia (Geoscience Australia) 2017;
• Austria terrain data © offene Daten Österreichs – Digitales Geländemodell (DGM)
  Österreich;
• Canada terrain data contains information licensed under the Open Government
  Licence – Canada;
• Europe terrain data produced using Copernicus data and information funded by the
  European Union - EU-DEM layers;
• Global ETOPO1 terrain data U.S. National Oceanic and Atmospheric Administration
• Mexico terrain data source: INEGI, Continental relief, 2016;
• New Zealand terrain data Copyright 2011 Crown copyright (c) Land Information New
  Zealand and the New Zealand Government (All rights reserved);
• Norway terrain data © Kartverket;
• United Kingdom terrain data © Environment Agency copyright and/or database right
  2015. All rights reserved;
• United States 3DEP (formerly NED) and global GMTED2010 and SRTM terrain data
  courtesy of the U.S. Geological Survey.

Thank you also to Glenn Randall and Moritz Gyssler for taking the time to try out and share feedback on these new features.

Next up: Using Photo Ephemeris Web, Part 10: Shooting Buildings and Other Objects