Wednesday, October 30, 2019

Seeing the Big Picture | Simplifying Route Navigation with the Garmin InReach Mini

If the YouTube search results are to be believed, David Goggins is a beast. And yet, on one of his recent adventures he made a classic tactical error: he got lost. It took him something like 12 hours and 28 miles to correct his error.

So while nearly all of David Goggins' feats are out of reach, this one I can totally identify with.

Goggins started his challenge with a device that displayed every waypoint he would encounter. He may simply have neglected to check his phone, which would have shown he made an obvious wrong turn. Or perhaps the phone was on the fritz and was giving him bogus GPS readings. Or maybe his phone got damaged, as it did with this luckless fastpacker:

After filming myself saying "I’m about to start my Long Trail FKT attempt. The time is 5:55am, I have until 11:20pm on Thursday 13th to make it to Canada", I put my phone down on the rock so I had a free hand to slap some mosquitoes. Seconds later I watched it slide down the rock and into the mud. My inreach pinged and I left. 100 yards into it, I went to check my phone and the screen was cracked and none responsive. It wasn't even 6am yet and I’d already run in to my first major problem.

Whatever the cause of Goggins' error was, it could almost certainly have been mitigated if he'd used a backup navigation device. In my case, that means loading the waypoints for my trip into both my phone and my Garmin InReach Mini. I primarily carry the InReach for its messaging capabilities, but its ability to direct you to a waypoint means that it can serve double duty. Add to the fact that its can receive in-field weather updates, and it's value as a device goes up even further.

One challenge I have when using my InReach for navigation is that it doesn't provide an overall map view. It will gladly route me to any waypoint it has recorded, including waypoints I may capture on the fly, but its silent as to where I am in terms of the big picture.

I thought about different ways to address this and came up with the following approach. Say I'm planning a West Virginia backpacking trip and I've got a bunch of waypoints:

Point Latitude Longitude
P1 38.713948 -79.633575
P2 38.704731 -79.62324
P3 38.700589 -79.602883
P4 38.697418 -79.582321
P5 38.699603 -79.581602
P6 38.69036 -79.566269
P7 38.705401 -79.55281
P8 38.71179 -79.54994
P9 38.751097 -79.517305
P10 38.732984 -79.600516

If I could plot those points on a simple grid, and printed out this grid, I'd have an overview which may be helpful for navigation purposes. This turned out to be easy to do in Google Sheets. I started off by converting the latitude and longitude values into UTM coordinates. I used the strategy outlined here to do this. Essentially, you grab this JavaScript library and wrap it up in an Sheets AppScript function.

Once I did this, I found my waypoints could be represented as UTM coordinates:

P1 17 618798.5526 4285919.941
P2 17 619712.5004 4284910.563
P3 17 621489.6755 4284477.713
P4 17 623283.2186 4284153.287
P5 17 623341.9928 4284396.73
P6 17 624691.4408 4283391.762
P7 17 625835.6589 4285079.309
P8 17 626073.9983 4285792.264
P9 17 628840.9109 4290199.752
P10 17 621640.5795 4288075.824

While these numbers look crazy, they're actually just meters East and North from an origin point. Using a bit of trivial math, it's possible to normalize these values into kilometers from the most South-East point.

Point East North
P1 0.000 2.528
P2 0.914 1.519
P3 2.691 1.086
P4 4.485 0.762
P5 4.543 1.005
P6 5.893 0.000
P7 7.037 1.688
P8 7.275 2.401
P9 10.042 6.808
P10 2.842 4.684

Using Google Sheets, I can plot these with an X/Y chart:

I could imagine printing out and laminating this chart to create an index-card sized overview of all the waypoints on a route. The plot is setup such that each grid space represents one kilometer, allowing me to easily estimate distances between points.

After going through the effort of creating this plot I realized I could also take the latitude, longitude and point names and import them into a Google 'My Map'. I could then print off a zoomed out view of the map and get something similar to my plot, only with map features visible:

Is the map view more valuable than my waypoint view? If so, then I all my UTM math was for not. Or maybe the two resources are most useful when combined. I could use the map view to help me understand the terrain, and the plot view to understand the distance between points.

Either way, I'm armed with an overview that simplifies navigating with the InReach Mini.

As for what happens if I simply neglect to check my navigational aids; that's a problem for another day. I may never conquer challenges on the scale of a David Goggins, but you best believe I'm going to learn from his missteps.

Here's are examples of the plot view, and map view.

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