APRS IN Your Pocket and Off Line Mapping
If you have assembled a APRS In Your Pocket" station like the one I describe in my article in the 2015 May edition of QST, there are a few things you should be aware of.........
This is a satellite view from aprs.fi of McKinnon Flats bordering the Bow River located at the end of Range Rd 274 south of Langdon AB.
Yes, the photos were all shot at McKinnon Flats, and more or less in the locations as noted.
On this day I was needing to do maintenance to my geocache located there, and while I made the hike in I was using my smartphone/Mobilinkd TNC/UV-3R to lay a track for reference work in regards to another project that I am working on.
Now those of you who are familiar with the Mobilinkd tnc and the fact that it requires an HT and your smartphone loaded with APRSdroid to function, are also aware that if your smartphone is not seeing a cell tower, you do not have access to Google maps.
It's easy enough to fix this by downloading offline maps to your phone, and in my case I have open-street-maps loaded on the SD card of my phone for exactly this reason.
In fact I use off line open-street-maps all the time with my smartphone running APRSdroid, as I find myself in situations like this regularly.
McKinnon Flats fits the description of "service unavailable", as the deep valley that it is located in blocks access to any cell towers off in the distance.
I left my mobile parked where you can see my callsign (VE6AB) printed on the satellite view, and carrying my smarthphone/UV-3R/Mobilinkd tnc, set up for manually beaconing through my Kenwood D710A located in my mobile.
A fill in digi was required as my tiny APRS in my pocket station with its 2 watts output would not be heard by a distant digipeater otherwise.
But what I forgot to do was turn off the Network location option in APRSdroid loaded on my phone that allows the use of GSM/3G and WiFi networks to obtain my position.
The reason that I use the Network location option, is that it does not drain the battery of my smartphone as quickly as leaving the GPS running full time.
The better option under the circumstances that I found myself in on this day, would have been to allow the GPS receiver in my phone to activate for 30 seconds at a time to get a fix, and then shut off again until required again.
So with no solid Network fix for the gps, the data received was not very precise as you can see by my waypoints in the Bow River, when I was actually walking on the shoreline.
Needles to say it goes without saying that the whole track is not located precisely where it should be because of my forgetting to switch to the better GPS option..
So lesson learned, check your equipment before striking out for distant horizons.
In my case I enjoyed my hike out and about, but if I needed a precise track, well I can go back and do it all over again with the GPS in my phone configured properly next time!
Click on the photo for a closer look....