There are occasions when a photographer, cinematographer, astronomer, pilot, or architect needs to know a lot more about the Sun's position than simply sunrise and sunset. Sun Seeker by Ajnaware Pty Ltd in Sydney, Australia tells you almost everything you can know about the position of the Sun for any day of the year. Plus, augmented reality allows you to find the Sun even on a cloudy day.
The full name is "Sun Seeker: 3D Augmented Reality Viewer," but there's much more. The best way to kick off is to list the kinds of data you can quickly call up.
- Local sunrise and sunset for any date
- The track of the Sun across the sky, azimuth & elevation
- Hours & minutes of daylight & Solar noon
- The highest elevation the Sun will reach
- Reference data for the summer and winter solstices
- The Air Mass for the light path through the atmosphere
- A graphic representation of the Sun's path over a compass
- A satellite and/or street map of your location with azimuth lines for the Sun as function of time of day
- Augmented Reality (AR) for the virtual Sun
- Export tabular data in CSV files for analysis
Why Would One Use This App?
There are times when photographers (or real estate agents) need to plan ahead for a shoot and preplan for sun angles. There are times when an architect needs to know the sun angles as a function of the time of year to design a building's eaves and glass design. There are times when an amateur astronomer may need to know where the Sun will be at a certain time -- without necessarily calling up a detailed Star Chart program like Sky Safari or settling for just the basic sunrise/sunset time, as in, say, Nav Clock. The augmented reality function allows the navigator to find where the Sun actually is even if it's behind overcast skies or below the horizon.
This is an intensely visual app, so a visual tour is in order.
The main page shows your longitude (lambda), latitude (phi), sunrise and sunset times at the top combined with a compass view of the arc of the Sun through out the day in yellow. (Red and blue lines are for the solstices. An option.) At the bottom is the current azimuth and elevation of the Sun plus buttons for the major functions.
The "Today" button has options to select the date as well as view a really cool animation of how the Sun traces over the sky between the dates of the solstices. I liked that very visual feeling for the seasonal movement of the Sun.
The main page showing arc of sun for the day.
The Details button brings up a portal to tabular listings.
For example, here's the sunrise/sunset data for part of March 2013 in Denver. Note March 10, when, in our neck of the woods, we changed to Daylight Saving Time (DST).
Note jump on March 10 when Denver went to DST.
If you want to chart the tabular path of the Sun in azimuth and elevation, select "Today's solar path."
Time shading changes when the Sun breaks the horizon.
If you have a specific geographic site in mind and want to see how the Sun's rays will track across the site, use the Map functions. This could be useful for home builders who want to layout a floor plan correctly to take avantage of morning sun in, say, the bedroom or sunset views from the living room.
The user can opt for light azimuth lines over time.
Augmented reality allows you to find the location of the Sun even when it's not visible. For example, I went outside and Sun Seeker showed me that the Sun was just behind the eaves of my house.
Find the sun location even when blocked.
For effect, I stepped aside a meter. Lo and behold, the real Sun and the virtual Sun coincided. Nice to see.
Step aside and the virtual Sun and real Sun overlap.
At the top of the main page is a small "i" that introduces the user to the app, nicely explains how to interpret all the displays and links to the developer's website. I liked that. And there's more.
I should note that this app makes use of the iDevice's magnetometer and GPS, and you may need to do a compass calibration, that figure 8 maneuver, to make sure your compass is working right. There is more discussion of this below.
Docs, links & email are easy to find.
I noted that the developer used the term "Path length" of the Sun's rays through the atmosphere. This is a specific technical term in astronomy, called Air Mass, and he told me he's going to change the language to reflect that astronomical usage.
Finally, there is a direct email link the developer which is always great. I don't like it when developers of technical apps try to hide from the customer.
Technical Sanity Check
I did some cursory technical checking of the sunrise and sunset times. I compared the app's predictions to a table I printed from the U.S. Naval Observatory. There, you can obtain lots of specific astronomical data, output to tables for your location. (It was faster than using Sky Safari for multiple dates.) Accounting for the small difference in my actual location and Denver, Colorado, the tables matched for the dozen or so dates I checked in 2013.
Partial USNO screen shot for sanity check. Note, DST is not used in these tables.
I asked the developer about his methodology. He wrote me: "The app does full astronomical calculation of the Sun's position for any given time, latitude and longitude, calculated on the basis of the VSOP87 theory This provides accuracy to better than a second of arc in calculated positions, and spherical geometry formulae are used to convert coordinates from celestial to equatorial and local horizon (azimuth and altitude)."
There is no app Setting for Daylight Saving Time, on/off, so I asked the developer how he accounts for those changes in all the various nations and locations. He wrote: "Fortunately there is a simple solution to this issue -- iOS contains a complete implementation of the Olsen timezone database. This means that, provided the correct timezone tag is known for any given location, updates to iOS itself keep this part of the app working correctly, including for future changes in DST.
Each of the app's 40,000+ built-in locations already contains it's correct timezone tag. The only issue would be if a particular location actually changes from one DST area to another -- rare, but it does sometimes happen. In that case the user can edit the timezone tag themselves, or else they can wait for me to issue an app update with updated location database.
The developer also offered some technical feedback on why some users may not see the virtual Sun in the exact location as the real Sun, as I showed above. He wrote:
The app's solar calculation is very accurate (typically better than 1 second of arc in the Sun's position), but the weak link in the chain is the device's magnetometer which is prone to two types of issues
1) If there is any magnetic interference, then (like a standard needle compass) the device compass will be adversely affected. For example being inside a car will likely cause major deviations to compass readings, but also being near a computer or electrical device may do too.
2) The magnetometer can drift and become mis-calibrated. Usually, if the mis-calibration is quite bad, the device will detect this and issue a prompt telling you to move the device in a figure eight to improve its calibration. However, it may be possible to calibrate much more effectively than this. Here is a video clip explaining how you can calibrate the compass to get optimum performance. Doing this should ensure that you get best possible accuracy from Sun Seeker, as well as from all other apps that use the magnetometer.
All in all, I was impressed with the technical background and professionalism of the developer, and I trust and recommend the output of this app.
Sun Seeker was released on 4 October 2009. It is now at version 2.8, released on 25 March 2013 and requires iOS 5.0 or later. It is a universal app and requires an iPhone back to 3GS or any iPad. The iPod touch is not supported because it has no magnetometer. Sun Seeker has been localized to English, French, German and Japanese.
I'd love to see the developer add daily times of civil, nautical and astronomical twilight to this already great app. Also, it wouldn't hurt to have the local time, digitally, on the main page.
Into the Sunset
This kind of app showcases what a technical developer can do with an iPad or iPhone and the iOS APIs. It's one of the reasons iDevices are so darn useful. And awesome. Plus, when a developer combines a great sense of aesthetics with astronomical calculations, the app can be breathtakingly beautiful, as Sun Seeker is.
More importantly, like scientific calculators, professionals depend on the results of an app like this. It requires some experience, technical expertise and developer professionalism to make sure an app like this can be trusted. From square one. I believe the developer has brought all those things together and created a beautiful, useful, delightful app.