Category Archives: Android GPS App


Who has used a tablet?

Can you post what your experience has been with BackCountry Navigator?

I am particularly interested in any stories from Dell Tablets because I have been talking to someone from Dell (they've been asking for my advice on their tablet strategy 😉  – no, not really). 

One suggestion from the survey was to make the software 'Galaxy Tab Friendly'. I don't know in what way it is unfriendly for Galaxy Tab yet. It looks okay in the emulator. 

I know there also many nonstandard tablets that don't have GPS.


Using Calibrated Digital Maps for Android Navigation

Occasionally people ask if they can use some of their existing map data in an Android GPS app like BackCountry Navigator.  

I am pleased to announce that there is software that allows you to convert a GeoTiff, or a number of other calibrated formats, to a mobile atlas that can be used by BackCountry Navigator. 

Take a look at MAPC2MAPC. This comes from a talented developer in the UK. 

There is also a nice tutorial here on using it for BackCountry Navigator. As one correction to the tutorial, I would copy the files to the destination *before* choosing the mobile atlas. By the time you read this, that may already be corrected:

Calibrated Maps for BackCountry Navigator for Android

Calibrated map images often are from existing collections that people have bought, or data posted on government websites.

The geotiff format, for example, consists of a .tif image file with a .tfw (world) file for calibration.  

Be patient when converting calibrated images – it may take longer than you think. There is lot of CPU and memory needed to reproject images and break them up into small pieces.

Some will ask why an Android GPS App can't just use geotiffs directly. The limitations of mobile devices will generally preclude this. It is common for geotiffs, for example, to be available at a size of 8192×8192. Try opening this size image on your Android device using the Gallery, or another image editing app of your choice, and it will probably choke. This is why Android mapping apps, including Google Maps and BackCountry Navigator, use maps in small pieces called tiles.

Others may ask if there is a way to convert a specific type of file. In some cases, this is not possible because the data is in a proprietary format that hasn't been well documented. This is usually data that people have purchased on CD-ROM, but occasionally, government data also comes in some of these closed formats. I don't know why the US Government would provide publicly owned data in formats that benefit commercial entities, such as .BSB and GeoPDF, but they do.   

If you have a question about formats or another question about MAPC2MAPC, be sure and ask the developer, who is very responsive and helpful. 


Android GPS Apps and Battery Life

Android GPS apps are often criticized for using battery life, when the mere fact that they use the GPS guarantees that they will. Battery life is especially important for those using Android GPS apps in an outdoor settings, such as hiking or hunting using Topo maps and GPS waypoints. 

Comments in the Android Market will say things "App is battery hog", "I would rate this app higher but it drained the battery a bit".  

You can often get the battery to last longer, and still get good use out of the Android GPS. Without any hardware changes, the solution, in oversimplified terms, is to use the GPS less.  

The following are measures that will work in conserving battery life with an Android GPS:

  • Turn off other radios you won't be using. This includes bluetooth, wifi, and the phone function. You turn off the phone function using Airplane mode. Due to a bug in Motorola devices, you should wait until you have your first fix, then turn on Airplane mode.
  • Turn the GPS function off when not in use, then on when you need a location. BackCountry Navigator has a button for this purpose. 

By turning the GPS on and off, I found that I was able to complete a three day backpacking trip using only 15% of the battery. The Android GPS still kept me from taking the wrong trail on several occasions. The first fix of the day took a minute or so, but I could turn it on later and find the new location in ten seconds or so.

Some have questioned why BackCountry Navigator has a "Start GPS" and "Stop GPS" button, instead of just using the GPS all the time as some other apps do. Be glad it is there. It is your greatest weapon against battery drain.  

The following are things that will not work, at least not completely, in getting more life from a battery when using an Android GPS: 

  • Turning off the screen with app(s) still using the GPS. Even if the screen is off, GPS updates will continue to consume battery life. The phone won't go completely to sleep in these cases. 
  • The app registers for less frequent updates. An app can specify that it wants to receive location updates every 5 seconds or every minute. While this sounds promising, it doesn't work. I've found that many devices will *never* get a satellite fix unless you set the updates to one second.
  • Changing the update frequency (min distance, time) for tracking. While there are other good reasons for having these adjustments, tracking is a scenario that requires the GPS to be constantly active.    

Here are some things that might work:

  • A fancy low power mode in the app that would turn the GPS on for long enough to get a solid fix, then off for a user specified period, then on again. It would require that you can get by with a minute or more between fixes. Again, this isn't really changing how much the GPS uses battery – it just changes how much you are using the GPS.  A lot more research and experimentation would be needed to see just how much battery this would save. 

Keep these things in mind as you spend time with an Android GPS in the outdoors, so you don't have your battery drain before you really need to know your location. And please write to the Android phone manufacturers to encourage them to use less battery in the GPS chip.  


Zooming in Topo Maps in Android

Often, I get questions from people who zoom in on a map and only see a blank grid. I'll show an example that will show how this may not be a bug.

Often the question is something like this: "Sometimes I zoom in on downloaded maps and all I see is a blank grid. What's wrong?" Often nothing. 

There is a key rule to keep in mind when you define a rectangle for download:

The download will download all tiles that *overlap* the defined rectangle, for all zoom levels.

In the following screen, I've just completed a small download. Here it is at zoom level 15, the highest detail I specified when downloading.

Detailed Topo map downloaded for offline use on Android   
This map adequately covers the rectangle I specified, plus more, so I should be extremely satisfied, right?

Now I'll try zooming out three levels to level 12. At this zoom level, the rectangle I specified overlaps exactly one (1) tile which covers a wide region. 

Zooming out on a topo map on Android

Again, this more than adequately covers the region I specified, so I should still be satisfied. Now the interesting stuff happens if I pan around this zoom level and then zoom in. If I zoom in on the green circle above, I should expect to see some more detailed map data.

However, if I zoom in on one of the red circles above, something happens which I may not expect. The map "disappears" and all I see is a blank grid. I could be disappointed, or think this is a bug, but why? After all, I got the region I asked for.

User Actions to help 
So if this isn't a bug, then what can a user do about it? Here are some suggestions:

  • Download a larger region. You could mark a rectangle that completely surrounds the one tile at zoom 12, and then you could expect to zoom in fully at those red circles.   
  • Turn off "Offline Maps Only" in the Map Source menu to go back into preview mode. Then you can at least preview the areas with red circles, and any tiles downloaded during preview will be saved. 

Where the App could help. 
The use of tiling in maps is here to stay. Nonetheless, there are some good suggestions users have made:

  • Show a coverage viewer that will allow you to see what your map currently covers. Presumably this will show a grid where darker squares indicate higher resolution. 
  • Show a grid and allow you to tap and choose tile squares instead of defining a rectangle. This will give you more predictable results, although it won't completely eliminate "zoom-in disappointment."    

Look for some of these ideas in surveys and future updates. 


Ordering a Printed Topo Map

It can be easy and helpful to order a paper topo map. This video explains how:

Order a Printed Topo Map

Although many of you have digital topo maps in your Android phone with BackCountry Navigator, it is helpful to have a paper topo map for the following reasons:

  • It is easier to see a larger area at once
  • It is easy to share amongst a group on a hike or backpacking trip. 
  • It is great for teaching map reading skills to members of the group. 
  • It saves battery life while using it for just browsing the area.  

MyTopo has been a great sponsor of BackCountry Navigator, and has provided, free of charge to you, access to its collection of shaded and enhanced topo maps for download to your phone.

MyTopo also can provide you a customized waterproof printed topo map, with much higher quality than you will ever get on your home inkjet. You can choose where you want it centered, whether to mix in aerial photography, and what kind of grid or tick marks you want to include. 

Today I created a video that shows you the process of ordering a printed, waterproof Topo Map from MyTopo.   

Watch the video on YouTube

Or try it yourself by ordering a topo map today!

I encourage everyone to order at least one map to show support for the maps we are using in BackCountry Navigator. To be compatible with your Android maps, order it in the datum NAD83 (which is the default anyway). 


Using UTM Coordinates in an Android GPS App.

What are UTM coordinates and what are they useful for? How can they be useful for entering waypoints for your Android GPS app? 

UTM stands for the Universal Transverse Mercator coordinate system. It is another way of specifying waypoints, in addition to longitude and latitude. 

Whether you want to use UTM coordinates depends on the source of your data. Many printed topo maps have grids in UTM. If you have a guidebook or other printed material that publishes coordinates in UTM, chances are you want to use UTM coordinates.

Why? Well, most people can't convert longitude and latitude to UTM in their head. In fact, a computer program to convert coordinates will often use several hundred lines of instructions.

Here is an example of entering coordinates in BackCountry Navigator. On the left are the coordinates in longitude and latitude. On the right is the same coordinate entered in UTM.  

Wntering waypoints on an Android PhoneEntering UTM coordinates of a waypoint in Android

This coordinate, 10 T 546542 5056337, has four parts total:

  • 10 refers to the UTM Zone, one of 60 zones on the earth.  
  • T is the latitude band. 
  • 5465422 is the EASTING value, measuring position in the horizontal direction. 
  • 5056337 is the Northing Value, measuring position in the vertical direction. 

The other reason why you would use UTM Coordinates in an Android GPS app is to be able to report your coordinates to someone else who is using UTM. Search and Rescue groups, for example, often like to use UTM Coordinates. 

When you turn on the UTM Coordinate setting in BackCountry Navigator, you will also see UTM Coordinates in the trip computer. 

UTM Coodinate setting in Android appUTM Coordinates as reported by the Android GPS.

Above, you can see that the longitude space, instead of degrees, contains a Zone, latitude band, and easting value, while the latitude space contains a northing value.

This is not all there is to learn about UTM coordinates, but hopefully this is useful to those using UTM coordinates on their Android phone.  


Using an Android GPS in Airplane Mode

Can you use the GPS on your Android phone in Airplane mode? This question frequently comes up, especially for Android users hiking with offline topo maps in the backcountry with spotty coverage.  

Please checkout GPS Airtime if you have one of the phones that have trouble. 

The benefits of using Airplane mode in backcountry trips are mainly for battery life. Turning off unneccessary signals is a great way to conserve battery life. When you are out hiking where your Android phone gets little or no cell coverage anyway, there's no use in your phone eating through battery life just trying to get a signal. And if you aren't going to be talking on the phone, you probably don't need bluetooth for your bluetooth headset. And since you won't run across many hot spots in the woods, you can leave wifi off too.

So by turning on Airplane Mode, you can eliminate battery use by cell signal, bluetooth, and wifi. But will the GPS work?

For me, the answer was yes. I did this with my Nexus One, and had no trouble turning on and off the GPS and got some great battery life. The first fix took less than a minute, and subsequent fixes took less than 10 seconds. The longest time to fix was about 2 minutes under heavy tree cover after 24 hours without using the GPS.

I asked about Airplane Mode and GPS in my last newsletter, and the results were staggering. It only took a handful of responses to establish a definite trend.

HTC vs Motorola
If your device is made by HTC, including the Nexus One, Droid Incredible, Evo, and many others, you probably said this:
My GPS works just fine in Airplane Mode.

If your device is made by Motorolla, including the Droid 2, or Droid X, you probably said this:
My phone had trouble getting a fix, or never got a fix, without the cell signal on, even if the signal was weak.  After the first fix I could generally turn it off and then navigate okay.
Those who reported this condition were often unsure if they would get a fix without cell signal if they waited long enough.   
Do either of these scenarios sound familiar? I don't have enough data to know what Samsung phones do yet. 

Unfortunately, I know what is likely happening with the Motorolla phones. They are using Assisted GPS, also known as A-GPS. By itself, this is a good thing, and allows you to get a faster fix when network coverage is available. Unfortunately, the idiots at the phone manufacturer haven't done a good job of making it work without cell coverage. This is not an unusual task. Standalone GPS devices and even bluetooth devices have been able to get a fix in less than a minute for several years now, and they've never had cell coverage. 

Does anyone live near Motorola Headquarters? I'd like to stage a protest. 

Don't blame BackCountry Navigator, or any other Android App, if you can't get a quick fix in airplane mode. This is appears to be in the hardware, or OEM specific code. 

This isn't the worst thing phone companies have done. Not too long ago, Verizon wanted to lock out the GPS in a Windows Mobile Phone to all but "approved" apps, in order to sell you their VZNavigator at $10/month. 

Hopefully, manufacturers will figure out sometime, we want to use the GPS in our Android phones as a GPS. Just like some antenna makers needed to figure out that some people use their iPhone as a phone


Finding Nearest Waypoints in Android

Today's newsletter talks about new features in BackCountry Navigator for waypoint lists, GPX import and export. Also included is response to feedback for finding maps, and other comments from the Android Market and surveys. 

There are some new features released today. Don't consider these features fully mature – they have been tested in house, but feedback from the field is welcome. If these are the features you have been waiting for, feel free to up your rating for the app.  

Waypoint Lists:
A highly requested and highly useful feature is the list of nearest waypoints. You can now find one on the fourth screen of BackCountry Navigator. 

This list will show the waypoints in the currently loaded trip file, if any.
To see a different set of waypoints, load a different trip file from the File menu.

You can also enter a keyword to filter waypoints and find a specific one by name . If the GPS is active, it will update the list based on the distance to you.   

Important tip: to see a menu for a waypoint, press and hold. You can then choose to edit, goto, center, or delete.  

GPX Import and Export 
Since file explorers are not standard on Android, I've now enabled a basic file explorer to import a GPX file from the file menu. There is also a GPX export menu item which will place GPX files in /sdcard/bcnav/out.  

Not all GPX files are created equal, so do email me any ones that don't work. It can often be something silly like a different date or color format that we can work around. Two have sent me some GPX files in the last week. One was found to be using some undocumented tags from Garmin, while the other ones were found to be a mystery so far since they all worked for me. But work continues. 

Finding a map you've downloaded
We've gotten feedback about some things that are not entirely clear. One is loading a map that you have previously download. While a download isn't a map that you can 'load', what you really need is to be able to get back to the same place where you have data. Related is the experience of loading a trip file and not seeing any visual confirmation. Here are some steps we have taken or will work on.

  • Place find caches coordinates: When you go to the Find a Place Menu, you can pick one of the suggestions with coordinate attached to skip the server lookup and recenter at the coordinates. 
  • AutoCenter when loading trip files: Now, when you load a trip file, the app tries to find bounds and come up with a default center and zoom. This won't help, though

    • The trip doesn't have any waypoints and tracks. (trip files do *not* contain map tiles). 
    • The waypoints aren't distributed in a way that has a meaningful center. 
  • Still tough: Missing storage card: When your storage card is unavailable, BCNav will fail in unpredictable ways without warning. Since registering for storage card events did not work as expected, a fix for this did not make it into this release.
  • Documentation: Note that our help docs have not yet kept pace with the new features. We hope to have some more examples out soon. Here is an example of importing GPX.

Response to Market feedback:
Since we don't have a good way of contacting people who leave comments in the Android Market. We also have some feedback through our survey, which doesn't allow us to contact members either.  Here are some things to think about:

  • Track Recording crashes?: Someone said that the app crashes when trying to start a track recording. Weeks ago, we did fix a bug that would fail in starting a track without a trip file.  
  • Could not find City: Our place find service goes through Google. It is unlikely that Google doesn't know about a city, so it is more likely that network connectivity is to blame if a search is unsuccessful.
  • Is BackCountry Navigator 'laggy'?: As obvious as this one sounds, I need some more help to figure this out. If some of you have found this app to be laggy, please contact me to describe. Some lags are caused by the map servers themselves, but others can be optimized. 
  • Could not import a GPX file: see above notes about GPX files. If you left that comment, could you please email that file to me? 

If you have had a good experience with BackCountry Navigator, consider leaving a positive comment on the DEMO or license app, to balance out those comments of those who probably need help, but that we may never be able to contact.  

Thanks and have a great day!