mirror of https://github.com/espruino/BangleApps
177 lines
6.5 KiB
Markdown
177 lines
6.5 KiB
Markdown
# Waypointer - navigate to waypoints
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The app is aimed at navigation whilst walking. Please note that it
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would be foolish in the extreme to rely on this as your only
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navigation aid!
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Please refer to the section on calibration of the compass. This
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should be done each time the app is going to be used.
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The main part of the display is a compass arrow that points in the
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direction you need to walk in. Once you have selected a waypoint a
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bearing from your current position (received from a GPS fix) is
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calculated and the compass is set to point in that direction. If the
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arrow is pointing to the left, turning left should straighten the arrow
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up so that it is pointing straight ahead.
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The large digits are the bearing from the current position. On the
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left is the distance to the waypoint in local units. The top of the
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display is a circular compass which displays the direction you will
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need to travel in to reach the selected waypoint. The blue text is
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the name of the current waypoint. NONE means that there is no
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waypoint set and so bearing and distance will remain at 0. To select
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a waypoint, press BTN2 (middle) and wait for the blue text to turn
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white. Then use BTN1 and BTN3 to select a waypoint. The waypoint
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choice is fixed by pressing BTN2 again. In the screen shot below a
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waypoint giving the location of Stone Henge has been selected.
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The screenshot above shows that Stone Henge is 259.9 miles from the
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current location. To travel towards Stone Henge I need to turn
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slightly left until the arrow is pointing straight ahead. As you
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continue to walk in the pointed direction you should see the distance
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to the waypoint reduce. The frequency of updates will depend on
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which settings you have used in the GPS.
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At the top of the screen you can see two widgets. These are the [GPS
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Power
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Widget](https://github.com/espruino/BangleApps/tree/master/apps/widgps)
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and the [Compass Power Indicator Widget]. These can be installed
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seperately and provide you a indication of when the GPS and Compass
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are switched on and drawing power.
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## Marking Waypoints
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The app lets you mark your current location as follows. There are
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vacant slots in the waypoint file which can be allocated a
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location. In the distributed waypoint file these are labelled WP0 to
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WP4. Select one of these - WP2 is shown below.
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Bearing and distance are both zero as WP2 has currently no GPS
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location associated with it. To mark the location, press BTN2.
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The app indicates that WP2 is now marked by adding the prefix @ to
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it's name. The distance should be small as shown in the screen shot
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as you have just marked your current location.
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## Waypoint JSON file
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When the app is loaded from the app loader, a file named
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`waypoints.json` is loaded along with the javascript etc. The file
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has the following contents:
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```
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[
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{
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"name":"NONE"
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},
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{
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"name":"No10",
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"lat":51.5032,
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"lon":-0.1269
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},
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{
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"name":"Stone",
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"lat":51.1788,
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"lon":-1.8260
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},
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{ "name":"WP0" },
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{ "name":"WP1" },
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{ "name":"WP2" },
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{ "name":"WP3" },
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{ "name":"WP4" }
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]
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```
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The file contains the initial NONE waypoint which is useful if you
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just want to display course and speed. The next two entries are
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waypoints to No 10 Downing Street and to Stone Henge - obtained from
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Google Maps. The last five entries are entries which can be *marked*.
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You add and delete entries using the Web IDE to load and then save
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the file from and to watch storage. The app itself does not limit the
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number of entries although it does load the entire file into RAM
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which will obviously limit this.
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## Waypoint Editor
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Clicking on the download icon of gpsnav in the app loader invokes the
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waypoint editor. The editor downloads and displays the current
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`waypoints.json` file. Clicking the `Edit` button beside an entry
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causes the entry to be deleted from the list and displayed in the
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edit boxes. It can be restored - by clicking the `Add waypoint`
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button. A new markable entry is created by using the `Add name`
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button. The edited `waypoints.json` file is uploaded to the Bangle by
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clicking the `Upload` button.
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## Calibration of the Compass
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The Compass should be calibrated before using the App to navigate to
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a waypoint (or a series of waypoints). To do this use either the
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Arrow Compass or the [Navigation
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Compass](https://github.com/espruino/BangleApps/tree/master/apps/magnav).
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Open the compass app and clicking on BTN3. The calibration process
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takes 30 seconds during which you should move the watch slowly
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through figures of 8. It is important that during calibration the
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watch is fully rotated around each of it axes. If the app does give
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the correct direction heading or is not stable with respect to tilt
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and roll - redo the calibration by pressing *BTN3*. Calibration data
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is recorded in a storage file named `magnav.json`.
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## Advantages and Disadvantages
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This approach has some advantages and disadvantages. First following
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the arrow is fairly easy to do and once the bearing has been
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established it does not matter if there is not another GPS fix for a
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while as the compass will continue to point in the general direction.
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Second the GPS will only supply a course to the waypoint (a bearing)
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once you are travelling above 8m/s or 28kph. This is not a practical
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walking speed. 5kmph is considered a marching pace.
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One disadvantage is that the compass is not very accurate. I have
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observed it being 20-30 degrees off when compared to a hiking
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compass. Sometime its is necessary to walk in the opposite direction
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for a bit to establish the correct direction to go in. The accuracy
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of the compass is impacted by the magnetic clamps on the charging
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cable, so it is particularly important that you recalibtrate the
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compass after the watch has been charged. That said I have found I
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am successfully able to follow a chain of waypoints as a route.
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## Possible Future Enhancements
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- Buzz when the GPS establishes its first fix.
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- Add a small LED to show the status of the GPS during the phase of
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establishing a first fix.
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- Add an option to calibrate the Compass without having to use the
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Arrow Compass or the Navigation Compass.
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- Investigate the accuracy of the Compass and how it changes
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throughout the day after the watch battery has been fully charged.
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- Investigate the possibility of setting the GPS in low speed mode so
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that a current course value can be obtained.
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- Buzz when you arrive within 20m of a waypoint to signify arrival
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## Acknowledgements
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The majority of the code in this application is a merge of
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[jeffmer's](https://github.com/jeffmer/JeffsBangleAppsDev) GPS
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Navigation and Compass Navigation Applications.
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