Table of Contents

1.   Purpose.                                                                    

2.   Overview.                                                                  

3.   Requirements and device options.                   

4.   Settings screen.                                                        

A.  Setting the Odo factor.                                           

B.   Minimum speed.                                                    

5.   Measuring distance.                                                

A.  Direction buttons.                                                  

B.   Numeric buttons.                                                  

C.   Split button.                                                         

6.   Data storage.                                                           

7.   GPS information.                                                    

A.  GPS accuracy.                                                       

B.   Installation and use of an external GPS receiver     

8.   Tech support                                                          

 1. Purpose 

The Mojo Odo app is designed to measure distance while traveling in a car.  The distance is reported in units of miles to a resolution of thousandths of a mile. 

    2.   Overview 

The app receives location updates from your device’s GPS once a second (or more frequently if you’re using an external GPS).  It uses this information to calculate the distance you’ve traveled and displays this value in miles in the Odometer. 

The app has 3 buttons that allow you to specify whether you are moving: Forward (adding mileage), Reverse (subtracting mileage), or Parked (no mileage is added even if you’re moving).

The app has an Odometer Factor that allows you to adjust the distance measured if you are running a car rally and want to adjust the app’s odometer to match the rallymaster’s odometer.

   3.   Requirements and device options 

This app will run on either an Android phone or an Android tablet. 

You can use either the device’s own internal GPS receiver (most Android devices have one) or you can use an external GPS receiver such as the Dual Skypro DGPS 160.  Using an external GPS receiver with any Android device requires the use of a “helper” app to allow your device to communicate with the external GPS receiver.  See details in Section 8B

All GPS apps consume more power than other apps, so we recommend that you keep your phone or tablet plugged into a power source.

   4.  Settings screen

The settings screen has two settings:  Odo factor and Minimum Speed.

Important note: The Odometer will be paused any time that you are in the Settings screen.  For this reason, you should only use the Settings screen while you are stopped.

A.   Setting the Odo factor

The Odo Factor is a number that is multiplied by every incremental distance calculated from the GPS location data.  An Odo Factor of 1.0000 means that we accept the distance calculated from GPS data without any adjustment.  An Odo Factor of 1.0100 (for example) would multiply every distance calculated from the GPS data by 1.01.  An Odo factor of 0.9990 would multiply every distance calculated from the GPS data by 0.999.

If you are a Rallymaster using Mojo Odo to measure your rally course, set the Odo Factor to 1.0000.  This means that the distance that Mojo Odo reports is exactly what is computed using the GPS information.  This is as close to statute mileage as we can get.  Push the “Go to Settings” button and then push the “RESET ODO FACTOR 1.000” button.  Then press the “RETURN TO MAIN SCREEN” button.

If you are competing in a rally, you’ll want to adjust Mojo Odo to match the Rallymaster’s odometer.  Follow these instructions:

1. Most rallies begin with an odometer calibration section that allows you to adjust your odometer to match the rallymaster’s odometer.  Make sure the ‘Split’ button is yellow.  If it’s not, press it once and it will turn yellow.  When your car is stopped at the starting line, press the red ‘Zero Odometer’ button in the lower left corner of the screen.  A window will pop up asking if you are sure you want to zero Odometer.  Touch “YES”. The Odometer should now read 0.000. 

2. Press the ‘Forward’ button and confirm that it is green.

3. Press the blue ‘GO TO SETTINGS’ button.  This takes you to a different screen.  Press the ‘RESET ODO FACTOR 1.0000’ button. Confirm that the displayed Odo factor is 1.0000.  Press the ‘Return to Main Screen’ button.  You will see the Odo factor of 1.0000 displayed in the Odo factor box.

4. Drive the odometer calibration section.

5. Stop your car precisely at the sign that ends the odometer calibration section.  Write down the app’s odometer reading on your route instructions.  Use a calculator to divide the rallymaster’s odometer value at that point by your app’s Odometer value.  Mulitply this result by the current Odo factor (1.0000 in this example). This number is your new odometer correction factor.

6. New Odo factor = Rallymaster’s odometer ÷ Mojo Odo odometer x current Odo factor

7. Press the blue ‘Go To Settings’ button.  Use the turquoise and yellow numeric buttons to change the Odo factor to the number on your calculator.  Confirm that the Odo factor is correct and press the blue ‘Return to Main Screen’ button.  (Do not press the red ‘Reset Odo Factor 1.0000’ by mistake.)

8. If the route instructions tell you to zero your odometer here, press the ‘Zero Odometer’ button.  Answer ‘YES’ to the ‘Are you sure’ question. Confirm that the Odometer now reads 0.000.  If the route instructions do not tell you to zero your odometer here (rare), use the turquoise and yellow numeric buttons to change your odometer to match the rallymaster’s official mileage.

9. Mojo Odo is now synchronized to the Rallymaster odometer.

              B.     Setting the Minimum speed

An unfortunate aspect of GPS receivers is that they don’t know when they’re stopped.  They continue to compute and update your location and send this data to the app.  If you examined this data, you would see that the GPS is reporting that you are continuing to move a small distance every second.  The amount of this erroneous distance is a function of the quality of your GPS.  (The better your GPS, the smaller is this erroneous distance.) This small distance typically would imply a speed of less than 1 mile per hour. 

If we didn’t detect this and adjust for it, your odometer would (erroneously) add distance while you’re stopped (that’s bad). 

If you touch the ‘Go To Setting’ button, you’ll see “Enter minimum speed”.  When you open this app for the very first time, this value is set to 1 (miles per hour).  With this setting, the app will reject any distance that the GPS reports where the reported speed is 1 mph or less.  If you are using an external GPS receiver like the Dual Skypro 160, this minimum speed setting of 1 mph should be sufficient to prevent adding mileage while you’re stopped.  If you are using your device’s internal GPS (most users will be doing this), the 1 mph setting may not be sufficient.

You should test the app on your device by going outside and waiting for the Accuracy value to stabilize.  Typically, the Accuracy on an Android device will stabilize somewhere between 3.0 and 3.8 (meters).  (The lower value, the better the accuracy.)  Once your device has stabilized Accuracy outside, zero your odometer.  (Don’t perform this test indoors.  GPS is very inaccurate indoors.)  Without moving, observe the Odometer.  If you can stand still for 1 minute and the Odometer still reads zero, you’re good to go.  If the Odometer adds distance while you’re standing still, you should increase the Minimum speed value.  Try 2 mph and repeat the test.  We recommend against setting the Minimum speed higher than 3 mph.  As you set this value higher, you will risk missing some mileage whenever you stop and then restart. 

If you find that at even 3 mph minimum speed your device adds mileage while you’re stopped, the best way to compensate for this is to press the ‘Park’ button when stopped for more than a few seconds.  But don’t forget to press ‘Forward’ before you start moving again!

   5.   Measuring distance

               A.   Direction buttons

                       1. Forward

When the ‘Forward’ button is pressed, it turns green and any distance travelled is added to the   Odometer.  This is the normal (typical) state of the Mojo Odo app.

 2. Reverse

3. When you go off course, you’ll either backup or turn around to go back.  In both of those cases, you’ll want to deduct the distance that you travel from the Odometer as you return to the point where you went off course.  If you touch the ‘Reverse’ button it turns red, and any distance travelled will be deducted from the Odometer.  Once you reach the point where you are back on course, touch the ‘Forward’ button (make sure it turns green) to resume adding distance to the Odometer.

4. Park

When you touch the ‘Park’ button, it turns orange and any distance travelled is ignored, whether you’re still moving or stopped.   You can still add or subtract mileage using the Numeric buttons, but any distance derived from the GPS will be ignored.

If you are going to be stopped for more than a couple of minutes (like for a break or for lunch), we recommend putting the app in ‘Park’ while you’re stopped.  Don’t forget to press ‘Forward’ when you return and before you start to move. (See section on GPS drift for explanation)

         B.    Numeric buttons

The turquoise numeric buttons add mileage to the Odometer.  The yellow Numeric buttons deduct mileage from the Odometer.

         C.   Split button

Pressing the yellow Split button turns it red and freezes the display of the Odometer, the Clock, and the Speed.  This allows you compare your Odometer reading to a mileage in the rally route instructions.  The Odometer continues to work (accumulate mileage) in the background whenever the Split button is red.

   6.  Data storage

Whenever this app is minimized or closed, the following data is automatically saved:  Odometer, Odo factor, and Minimum speed.  Whenever you open the app, these three values will be automatically reloaded.

   7.  GPS information

  A. GPS accuracy

The app displays the estimated GPS accuracy in small numbers just below the yellow ‘Split’ button.  This number is in units of meters and is an estimate of how far off the GPS reported location could be from your true location.  The smaller the number, the more accurate the GPS data. 

Android devices will typically report an accuracy between 3.0 meters and 3.8 meters as long as they have a good view of the sky. 

You should find a method to securely mount your device in the car in a way that provides the best (lowest number) accuracy.  Setting the device in the cup holder in the car’s console is not a good location because it has a poor view of the sky in that location.  For that reason, some users will choose to buy an external GPS receiver (such as the Dual Skypro 160 or Garmin Glo).  Those external receivers will sit comfortably on your car’s dash and will communicate with your phone/tablet via Bluetooth. 

Using a Dual Skypro 160 will typically provide an accuracy of 1.8 meters.  They also send location updates 10 times per second instead of the once per second of your phone/tablet’s internal GPS.

Using an external GPS receiver will provide more accurate information to your Mojo Odo app.  If you are measuring a rally, we strongly recommend using a Dual Skypro 160.

             B.   Installation and use of an external GPS receiver

The operating system of Android devices (both phones and tablets) will not automatically connect to a Dual Skypro 160 or any other external Bluetooth GPS receiver.  You need to install a “helper app” that will connect to the external GPS receiver.

There are several helper apps available on Google’s Play Store. The one that we recommend is “Bluetooth GPS” by GG MobLab.  Go to the Google Play Store and search for “Bluetooth GPS”.  If you see an app by that exact name by GG MobLab, download it and install it on your device. 

If you don’t see it in the Google Play Store, you can find it by Googling “Bluetooth GG MobLab”.  Choose the CNET website option that appears in the Google results.  Download the Bluetooth GPS app.  (There will be several “Download” buttons that are really links to ads.  Be careful to avoid them.)

Go to Settings on your device.  In the search field, search for “Build number”.  Tap on the result that appears to go to the Build Number in your Settings.  Tap on the words “Build number” seven times quickly.  A window should then appear announcing that you are now a Developer. 

Now search for “mock” in the search field.  You should see a result titled “Select mock location app”.  Touch this result to go there.  Now touch “Select mock location”.  You should see a list of possible choices.  The Bluetooth GPS app that you just downloaded should be in this list (it might be the only one in the list).  Touch it to select it.  You’ve now specified that your device can use that helper app to connect to an external GPS receiver.

In order to use your external GPS receiver, do the following:

-        Turn on your external GPS receiver.

-        Open your helper app (Bluetooth GPS)

-        Allow your external GPS receiver a minute to get a fix on the satellites.

-        In your helper app, choose “Connect”.

-        In a few moments, you should see data in the helper app indicating that it has connected with the GPS receiver.

-        On the Dual Skypro, you’ll see a solid blue light indicating that it has established a Bluetooth connection with a device.

-        Open Mojo Odo.

-        You should see an accuracy of less than (better than) 3 meters, typically just under 2 meters.  Make sure the GPS receiver is situated on your car’s dash, as far forward as possible to get the best view of the sky.

-        If you take your device away from your car (like at a break or at lunch), you’re likely to break the Bluetooth connection as Bluetooth has a maximum range of 30 feet.  We recommend leaving your device in the car at breaks to avoid breaking this Bluetooth connection and having to go through the connecting process again.

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     8.  Tech support

Email anydayrallies@gmail.com with any questions, problems, or suggestions.