Show HN: Augmented Reality App to Predict the Sun and Moon Location | Hacker News Reader

Show HN: Augmented Reality App to Predict the Sun and Moon Location

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Haven't tried anything like this recently so I was curious how accurate it was.

Here are two screenshots: http://imgur.com/a/8IM9s

I am impressed but there is some delay and lagging behind when moving the phone.

Thanks for giving it a try!

I'm using a low pass filter on the raw sensor data to minimize any jittery input.

The code I'm using is as follows:

  alpha = 0.1;
  output = previous_output + alpha * (new_input-previous_output);

If anyone knows a better way to get a stable and also current read-out, I would be more than interested!

I haven't implemented one myself, but Kalman filters are frequently used for this. Search HN's history to find several (presumably) good introductions.

Awesome! I'll check it out

Kalman filters can get really complicated (EKF, UKF, adaptive, etc etc) and needs to be tuned with the correct covariances.

Complementary filters works well enough and is very simple to implement even if you're a noob (e.g., high pass on accelerometer and low pass on gyro).

There's a lot of libraries that do the hard work for you though... Anyway, if an EKF is too much effort, you could also try the "Madgwick" filter:

Madgwick, S. O., Harrison, A. J., & Vaidyanathan, R. (2011). Estimation of imu and marg orientation using a gradient descent algorithm. In Proceedings of the IEEE International Conference on Rehabilitation Robotics

The Madgwick filter seems to be popular for gyroscope applications, this might be very helpful. Thanks!

I'm no expert, but when I had to make a cursor on the screen from Kinect hand location data I used what's called an exponential weighted average using output from an exponential moving average function on the raw data.

http://stackoverflow.com/questions/7947352/exponential-movin...

http://blogs.interknowlogy.com/2011/10/27/kinect-joint-smoot...

Worked pretty well!

That sounds very helpful! I'll give it a close read and see what I can come up with.

i think i small windowed median filter would do a good job in this case

I tried a small windowed mean filter, which gave really bad results. I'll try implementing the median filter.

Also be aware, that the accuracy is solely dependent on the accuracy of your device. If your compass is not correctly calibrated or there is any magnetic interference, the software can't do much.

I've wanted to make a progressive web app like this for a while for gardening. Way better execution than I could have accomplished in my spare time though!

My use case is, in the winter I want to be able to predict how many hours of sun various spots in my yard will have during the summer so I can plan where to plant things or dig new beds.

I actually started off with quite a similar use case in mind: when I moved into a new apartment a couple of month ago, I wanted to know how many hours of sun the plants on the balcony will be getting and when I could expect direct sunshine onto the balcony in the morning. And because I wanted to try my hands at Android programming for a long time, this was a good opportunity for such a project.

Here's a write up with all the features and more screenshots: http://genewarrior.blogspot.com/2016/10/sun-locator-predict-...

Looks great! Any particularly useful frameworks you used? Guessing the graphics are just OpenGL? I've started on something similar but for plane identification (mapping user location, phone orientation, and guessing what plane it is based on Flightradar data etc)

Thanks! Yes, the graphics are OpenGL, however I haven't used any frameworks. It's essentially a static scene showing the horizon, the elevation and azimuth lines, and the Sun/Moon sphere, while the camera sits in the origin and points to the location given by the compass/gyroscope.

Your project sounds cool, will you also be using OpenGL, or have you come up with another approach? I still don't feel very comfortable using OpenGL, it's a bit too complicated for my taste.

OpenGL. Yeah I didn't find it too great of an experience. Especially after finding out the myriad devices that are needed to support and their different OpenGL frameworks. Ended up just doing a PoC but gave up around the time I had to do the actual maths. With holidays coming up maybe I'll give it another shot. There's a company I think would find the app useful so it has a commercial reality too! Will check back in with you to see how you're going if I remember

Everyone in the industry tends to use Sunseeker, which is an AR sun mapping app that's been going strong since 2009. It's great you've made this, but I'm just not sure why I would use this over Sunseeker or Dark Sky.

When I started off, I didn't intent to compete against any existing apps; however I got quite some good feedback from friends so I decided to publish the app anyway.

Regarding Sunseeker: give Sun Locator a chance anyways! Although I'm obviously biased, I would say the Map view is streets ahead of sunseeker. Plus the free (lite) version is already much more useful and the pro version is still cheaper.

First, as the developer of one of the existing apps (Sun Surveyor) in the space, congratulations! Long time HN lurker; never expected to see this space come up here. My experience with it has been incredibly fulfilling, and I never knew about Sun Seeker et all (or the difficulty involved in some aspects) when I started or I may not have. I'd love to compare notes sometime.

Second, I see you have a lite and pro app. I'm curious what made you choose that model; when I released my app there were no IAPs, and now it's almost too troublesome to try to switch to that model for me. It's rare to see a non-IAP model these days so just curious how it's working out for you and your rationale! I certainly wish I could just have IAP.

Thanks for the encouraging words! I think Sun Surveyor is undisputed the top app in the space. It's really quite an instructive and interesting process to publish an app, try your hands at marketing, answer requests, work around at intricacies of different Android versions and device models. Coming from a background in academia and research, it's very fulfilling to see your app (even though it's comparatively simple) used by hundreds of people.

Regarding IAP: I'm not using in-app purchases. At the beginning I thought it to be too much of an effort to implement and now it's too late. So there are two separate apps available, the free version (shows data only for the current day) and the paid version (shows data for any day). I think this is similar to your app(?). I thought it would be easier to get users to try a free app and than upgrade instead of having to buy a paid app without getting to test the app beforehand. However the rate of people buying the pro version is rather low (around 3-4% of Lite users purchase the Pro version; I don't know what your experience is?)

Send me an email (contact@genewarrior.com) to compare notes, I'm definitely interested!

How does this compare with photopills?

I never tried photopills, I think it's iOS only. Besides the Augmented Reality feature, Sun Locator also has a map view that shows a 3D sun dial projecting the shadow on the chosen date/time that helps you to assess the shadow length and direction.

One thing that I think is the main advantage over other popular sun position apps is the ease of use, while still showing all the relevant information.

spoiler: this has nothing to do with Pokémon

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