Ajnaware’s Weblog

Web, Mobile & iPhone software development

HyperAltimeter – Barometer and Altitude Tracker

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HyperAltimeter

Here it is! I’m excited to present my first new app in a long, long time! It’s called HyperAltimeter, and it’s all about pressure and altitude, and pushing the limits of what can be done with the new barometer sensor that is embedded in your iPhone 6 or 6 Plus.

Whilst most smartphones are already equipped with GPS receivers, which do provide altitude readings, these are not typically very accurate. The GPS system is designed to obtain your horizontal position to a good degree of accuracy, but accuracy of altitude was not a key design factor.

However, the new barometer sensors are very sensitive, and can detect pressure changes as small as those experienced just by raising the device from your chest level to above your head. This means that it excels at measuring changes in height as you climb stairs, or walk or run a course.

However, longer term changes in pressure due to moving weather systems means that height changes can only be determined accurately over short periods of time, and similarly it also means that your altitude from sea level cannot be determined accurately from barometric data, alone.

The solution to longer term accuracy in height changes and absolute altitude measurement comes from combining the device’s barometric data with weather data i.e. readings of local pressure and temperature.

Amazingly, from first idea to this app becoming available in the app store was just six days! I’ve typically spent one to three months developing each new app, and then many more months, over time, enhancing and refining them. But in this case, by leverage code and experience from my other apps, I submitted the app to Apple after just five days. And then Apple’s approval came within twelve hours. By comparison, review time for app submissions is currently averaging about twelve days. So it seems Apple is especially keen to help along apps that make use of the iPhone 6’s new capabilities.


 

About the App

This app measures your altitude via three very different means (or via two means if your device doesn’t have a barometer sensor). This allows much greater accuracy than relying only on the device GPS sensor alone to find your altitude.

In fact the standard GPS readings of altitude are far less accurate than the other two methods, so it is provided here mainly just for the sake of comparison.

The three methods are:

  1. GPS sensor
  2. Online mapping survey data
  3. Barometer sensor combined with current local atmospheric conditions

Altimeter Screen

This screen shows all available altitude-related data, as well as showing your current location on a map. The displayed data items are:

  • GPS Altitude – this is the altitude from the standard GPS sensor. Note that the given accuracy is one returned by the sensor, although by observation the stated accuracy range is sometimes too small, and does not overlap the more accurate measurement taken via the two other methods.
  • Map Altitude + Δh – This shows the altitude for your current location as determined via online mapping data. It is generally very accurate in relation to gound level. If you are in a high-rise, use the Height Above Ground field to enter your local height – this will automatically then be included in the altitude value shown in this field.
  • Barometric Altitude – Barometer sensor combined with current local atmospheric conditions (means sea level pressure and temperature), which are then used to calculate your actual altitude. Note – this method is only available on devices which include a barometer sensor.
  • Device Pressure – Shows the actual pressure reading from the device barometer, as used in the altitude calculation.
  • MSL Pressure – Shows the mean sea level pressure from the nearest available weather observation location, as used in the barometric altitude calculation. Tap on this cell to see detailed information about the local weather data it is currently using.
  • Height Above Ground (Δh) – this is a value you must enter yourself, if you are in a high-rise building or otherwise abve local ground level, and is used to refine the the Map Altitude calculation, above.

 

Screen Shot 2014-10-17 at 1.09.06 pm

 

Graph Screen

This view allows you to see how altitude is changing with time, via a constantly updating graph. The three option are:

  • GPS Altitude – Shows the altitude data returned by the device GPS sensor.
  • Barometric Altitude – Barometer sensor combined with current local atmospheric conditions (means sea level pressure and temperature), which are then used to calculate your actual altitude. This value is retrospectively adjusted when each new local mean sea level pressure reading is obtained, to take account of the atmospheric pressure trend. Due to these adjustments, this graph should show reasonable stability over the long term.
  • Δ Altitude – Shows the relative difference in altitude from when you first started the app, or tap the reset button, based on changes in pressure. This is very accurate for measuring short-term altitude changes, such as going up or down stairs, taking short walks or runs across terrain etc. Over longer time periods it will likely suffer from drift due to changes in atmospheric pressure, due to moving weather systems. For this reason you may want to reset this graph just before using it to make a measurement of change in your altitude.
  • Pressure – Shows the raw pressure readings from the barometer in your device. This value changes over time for two reasons – one is when you move up or down, as pressure changes with your altitude, and the other is changes in local atmospheric pressure due to weather systems and wind gusts. If you keep the device stationary, then this graph will reflect only atmospheric pressure changes.

 

Screen Shot 2014-10-20 at 7.31.11 am

Screen Shot 2014-10-17 at 1.11.10 pm

 

So what are you waiting for? Go and get it from Apple’s app store!

Written by ajnaware

Monday, 20 October 2014 at 8:58 am

Sun Seeker – How to use the new azimuth calibration feature

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I’ve just submitted an update to Sun Seeker for iOS – v4.3.

This update contains an experimental feature which addresses one of the most difficult aspects of using the device’s compass to obtain an accurate heading, when using the augmented reality 3D view to see the solar path. This article seeks to explain what this feature is about, and how best to use it.

Note that the Android version of Sun Seeker does not yet have this feature. I will be relying on feedback from iOS users before deciding whether to implement it in the Android version.

In the last major release (v4.2), I introduced the ability to toggle between Compass+Gyroscope mode and Gyroscope-only mode. This was already a big leap forward, because the gyroscope-only mode allows users to manually adjust the 3D View heading simply by dragging it manually.

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The gyroscope-only mode allows you to set the heading manually, and the device then holds your setting relative to the gyroscope. Although there is likely to be a slow drifting of the gyroscope-only data, provided that you were able to set the heading accurately, this will work well for short periods of time – more than likely long enough to get all the information you need from the app.

Of course this all depends on you being able to set the heading accurately yourself. If the sun is out, then this is very easy – just line up the sun icon in the camera view with the actual position of the sun! Easy. :-)

But what if the sun isn’t out? Well this is where the new “Azimuth Finder” feature comes in. Tap on the settings (gear) icon in the 3D View, and you will see two new options at the bottom of the list of settings.

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  • Show Reference Azimuth – If you have already selected a location, use this option to to toggle the display of an azimuth line corresponding to the selected location.
  • Set Reference Location – Tap this to open the “Azimuth Finder” view, and select a location or landmark within your line of sight, to use for your reference azimuth.

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All you have to do in this view is to use the map to browse to a landmark or location that is visible from where you are now. It must be somewhere that you can identify when looking later through the 3D camera overlay view. When you have found a suitable location, just tap and hold to drop a marker. The app will use geocoding to assign a name or address to the location, and calculate it’s azimuth from the current device location.

In this particular example, I am (just) able to see the top of the Sydney Harbour Bridge from here, despite the rain and low cloud, so that makes a good landmark to use.

Then, as soon as you tap “Done“, you are returned to the 3D View, and there is now a new line showing the azimuth of the selected location. Note that you will only see this line if you are already looking in approximately the right direction! Otherwise you may need to pan around until you bring it into view.

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You may be able to make out the Sydney Harbour Bridge in this screenshot – just to the right of the chimney, directly below the centre cursor.

As this 3D View is already in gyroscope-only mode, all I needed to do next was to manually drag the white azimuth line to the actual location of the bridge – in this case four degrees to the right. And, voila, we now have a very well-calibrated heading!

Note that if you leave this for a while it may drift off again little by little, due to gyroscope drift. In that case, simply repeat the same calibration procedure.

Once you’ve selected a particular landmark for calibration, it is remembered (and the heading automatically adjusts itself if you change location yourself), so you can just switch the reference azimuth line on or off via the settings icon. And at any time you can choose a different reference location too, as you will obviously need to do if you move to a new location from which the original landmark is not visible.

Written by ajnaware

Tuesday, 19 August 2014 at 11:09 am

Oz Weather Plus – Why I’m releasing it as a new app

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The Oz Weather iPhone app was first released on 20th Nov 2008 – yes that’s more than 5 years ago!!! By all accounts, it’s been a highly successful app. Notably, in January 2009, it reached #1 ranking for paid apps in the Australian app store and stayed there for about 10 days, during the period of an intense heatwave, and deadly bush-fires. And over the entire 5 year period, the app has been installed onto hundreds of thousands of devices.

There have also been more than 30 free app updates released during that period, and also an attempt to use in-app purchase to provide new, advanced features, which were much appreciated by a number of users. This also attracted a lot of very negative and vocal feedback from users who thought they should be getting it all for free, and as a result I eventually re-integrated those features into the app and removed the in-app purchase. But the damage was done, and with a competitor who crowed loudly that their own app’s updates would be free forever (they’ve since reneged of course), Oz Weather lost its lead in the app store to them.

And here’s how Oz Weather sales have gone, over the last few years…

Sales_2010_2013

So as you see, despite the many app updates (seen as comments bubbles in the above graphic) new sales have trailed off considerably. There are a number of reasons for this. The biggest one is that competition has increased a lot over the years. In fact it seems that my own openness in posting my app’s sales figures during those early years probably encouraged quite a few other developers to try their hand at it. And then there were the bigger players in the Australian weather field, such as “WeatherZone” and “Elders Weather”, who had just been slow to get into the app store, and eventually figured out how to make their apps more appealing. Some of those competitors innovated with new types of features that I didn’t think would be as appealing to users as they actually turned out to be. More recently still, it seems to have become something of a trend amongst app developers to use weather apps as a kind of test playground for new app design paradigms. And there have indeed been some really nicely-designed weather apps coming out, especially with iOS7 style interfaces.

And it is indeed the iOS7 operating system update that finally prompted me to consider starting afresh. And with this impetus, suddenly there was a surge of new enthusiasm to create several innovative new features, some of which had been floating around in the back of my head for years, but not seen the light of day due to lack of motivation stemming from the various issues described above.

The big issue was, of course, whether or not this could or should be offered as a (necessarily free) update to the existing Oz Weather app, as opposed to creating a brand new app. I’m sure readers of this post will be well aware of the many precedents for creating new apps as opposed to providing free updates – the first big one of which was Tweetie – and they got some really bad reactions, although over time there has been greater and greater acceptance that this is pretty much a necessary way to go in order for app developers to survive, in particular given the shortcomings of in-app purchases, and the fact that they simply aren’t workable in many types of non-game category apps.

A key metric to consider in my own case is that I’ve spent around 1000hrs building the new app and its associated server code. Even if I were to value my time with only a modest hourly rate, at the current rate of app sales, it would take much more than a year of ongoing income, in fact maybe several years, to pay for the time I’ve invested in it. Obviously that would not be a sustainable way to work or run a business.

Also, many of the existing Oz Weather users bought the app more than 3 years ago – most of them paid around $2.49 for it, although it’s since gone down to $1.99 due to Apple changed pricing tiers, combined with ongoing downward price pressure from the competitors. Further, many users do continue to use the app on a daily basis – so it would be hard for them to argue that they haven’t got good value for money.

Then, of course there are those users – a much smaller number – who bought the app more recently – and it will probably feel less fair to them not to be getting a free upgrade. However, I am not intending to stop providing data feeds to the existing app, at least for the foreseeable future. (I don’t want to make any rash promises that I might not be able to honour – it might be necessary to drop the feed at some point down the line.) So those users will continue to have a fully-featured, working app – the same features that were advertised to them in the app store, and which they paid for. I do know it will suck a little bit more for those who bought it only really recently. So if you really feel that badly about paying for the upgrade, and are financially stressed by it, what the hell, why not send me an email, via the app’s About / Email us button, and if you really make a good case, I’ll see if I can help out.

There it is – that is why I’m releasing the new version of Oz Weather as a new app. For better or for worse. So may god help me. Amen. ;-)

Written by ajnaware

Wednesday, 20 November 2013 at 4:56 pm

Sun Seeker Sizzles!

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The Sun Seeker app has continued to be enhanced and honed in a series of updates, the most recent being v2.8, which includes a modernised interface – yep, those are indeed flat button faces. ;-)

Sun Seeker v2.8 compass screen

Sun Seeker v2.8 Compass Screen

These updates seem to have attracted a bit of positive attention resulting in several new blog reviews, culminating in the following fabulous review from top-notch reviewer John Martellaro (@jmartellaro) of The Mac Observer. This is a must-read review, not just because it is positively glowing, but also because John saw fit to include my detailed answers to his probing questions, including some inside information on how the app works, and especially importantly on how to ensure optimum compass calibration of your device.

Just to show a little more of the app here, my own favorite feature update is the ability to select date and time on the map view via a scroller.

Sun Seeker Map View

 

Written by ajnaware

Thursday, 4 April 2013 at 4:17 pm

Sun Seeker for Android!

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After a long development period I’m delighted to announce that Sun Seeker is now finally available for Android devices!

Click on this logo to see it in the Android Marketplace.

Available in Android Market


Is is real or is it Memorex? (You have to be of a certain age to remember that advertising slogan!)

Yes – it looks just like the iPhone version in most ways, and includes all the same features as the latest iPhone version.

I’m especially interested to see how sales go, and find out just how different the app sales may be between the two devices. Of course Sun Seeker on iPhone is well established, and it may take a while for the Android version to find its momentum. We’ll see!

Written by ajnaware

Thursday, 1 March 2012 at 4:07 pm

Posted in Uncategorized

Sun Seeker Test Shots

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Here are a couple of images from Sun Seeker put together (unsolicited) by a generous and enthusiastic New York based photographer/cinematographer – Hal Hansen.

He’s currently revamping his website and I’ll provide a link to it here when it’s ready. Thanks Hal!

I love the way he’s featured an iconic yellow cab which is a New York signature. Did anyone notice that it’s not actually the same cab in each shot? That’s clever photography! ;-)

Written by ajnaware

Thursday, 24 March 2011 at 3:20 pm

Posted in iPad, iPhone, Software & Hardware

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Sun Seeker Update v1.5

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As part of a series of planned updates for the Sun Seeker augmented reality iPhone app, the latest update v1.5 has just been approved by Apple.

For a video demo of Sun Seeker see this earlier blog post.

The main changes for v1.5 are:

  • Enhanced performance for smoother compass dial rotation
  • Added new table of annual rise and set times
  • Added new table of sun’s daily azimuth and elevation
  • Added tap action to rise/set label to see local times instead of intervals
  • Better handling of disabled Location Services
  • More efficient use of GPS – now only used briefly on startup
  • Fixed some minor bugs and issues with date changes

[Note - v1.5.1 update has been submitted to fix OS3.0 backward compatibility and missing sunset times for some locations west of GMT.]

Following is a more detailed description of some of these items.

1. Enhanced Compass Dial Rotation

The compass dial in Sun Seeker includes text which retains its orientation relative to the device regardless of the compass rotation, and this means that at least part of the image needs to be re-rendered for each incremental rotation of that dial as the compass rotates. Previously the whole image was being redrawn each time, and that performance hit meant that the dial motion was quite jerky when it needed to make large rotational changes. The new implementation involves much less redrawing, and hence allows the compass to be much more responsive.

2. New Tables

The table of rise and set times spans the entire year, and hence allows you to look up rise and set times for any given date.

The table of the solar path lists the sun’s azimuth and elevation at 15 minutes intervals throughout the currently selected day.

3. Tap action to see rise/set time instead of intervals

This was added simply for clarity. Tapping on the rise/set labels on the compass screen toggles the display between showing the rise and set time in local time versus showing time duration between now and the rise and set times.

4. Better handling of Location Services status

A problem to date has been if the user has switched off the device Location Services or (perhaps accidentally) disabled them for this particular app. In these cases the app can only use its last acquired location data, and in this case the app shows data which is correct for that old location, but incorrect for the user’s current location.

This issue has been the biggest generator of email support requests to date, but I now expect that this will lessen considerably, because I have implemented clear warning messages which pop-up whenever location services are disabled, each time that the app starts up or resumes from background.

5. More efficient use of GPS

Previous versions of the app left GPS on continuously while the app was active (although off when inactive or in background), and this presented the app with ongoing positional updates while it was open. But for the sake of efficient use of GPS, it seemed unnecessary to leave it on once the location had been determined to a reasonable accuracy, so GPS is now only on as long as location has not been found to reasonable accuracy. However an important point here is that the app should re-query its location not only every time it starts up, but also whenever it resumes from background. The reason for this of course is that the device may have changed location while it was in background – for example it may resume from background after the user has traveled somewhere by air!

6. Future Updates

By far the most common request from users has been to allow selection of other cities/locations rather than just the current current, and this is the next major feature planned. But please note that it is not a trivial update! A particular difficulty here is in ensuring that the local times reported for other locations respect the correct timezones and daylight savings rules for those locations throughout the year. However, I do have a solution planned, and hope to be able to do this within a reasonable timeframe.

The next most common request has been for an Android version. Due to the particularly technical nature of the app, and the fact that I personally have no grounding in Android development, this is a much more difficult proposition. However I have been looking to outsource it. I apologise to those who have been waiting impatiently, and I can assure you that these plans are progressing.

In the meantime, I hope you continue to enjoy the app!

Written by ajnaware

Saturday, 19 March 2011 at 12:18 pm

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