SnowSlider – Blogging From the mountains by ise

Towards the end of the ski season I got the Garmin eTrex Vista Cx GPS unit which I’ve mentioned before and been using to produce some track files for viewing in Google Earth. The real reason I bought this was for navigation, I’d had an older GPS a few years back prior to the removal of selective availability when it really just didn’t work accurately enough. Yet again I was dubious, this time about GPS for navigation, my problem is that I believe nothing can be a substitute for being able to read a map and navigate in the mountains with map and compass regardless of the weather conditions. However, map and compass aren’t always quick to use and a couple of off-piste trips skiing alone when the visibility was appalling made me think a GPS might be useful particularly if I saved some common local waypoints onto it.

I opted for the Garmin eTrex Vista Cx as it was a mid-range mapping unit with a barometric altimeter and electronic compass included. Most GPS can tell you altitude but they’re not renowned for their accuracy so you really need a barometric altimeter if you want some accuracy. I’ve also got the SwissTopo maps for the device for the whole of Switzerland which are in the proprietary Garmin format for use with the MapSource product.

The software has been a nightmare, when I first tried to initialise the maps the Garmin server wasn’t working and I couldn’t unlock them. You need two different keys as well, one to get the maps installed onto your PC and another to unlock them to get them onto the device. Later when I moved computer the registration failed, as I’d already installed on my old desktop and laptop, so I had to call a premium rate line to get it re-enabled, this is common practice in the software industry now, for example Microsoft do it, but Microsoft are pretty slick so while the principle is irritating at least the practice isn’t. The Garmin principle and practice was irritating though.

A Field Trial on a Ski Tour

This is from a short ski-tour I took back in April (Grimentz – col de Torrent) round the local area. The blue line is my planned route and the red is the actual track recorded by the GPS. The numbers along the blue route are the waypoints I’ve entered, I number these in gaps of ten to allow me to insert more points later.

To plan the route I used the Garmin MapSource software, this works pretty well once you’ve actually got all the maps together and unlocked. I worked from the SwissTopo paper map and took coordinates from it. SwissTopo have specialist Ski Tour maps, the blue ones if you see them in the shops. These have much more information than the maps on the GPS. The Ski Tour maps mark established ski routes and reference them to the CAS (Swiss Alpine Club) area guides which contain route descriptions. The maps also mark huts and have a notation to show risk areas for steeper slopes, in short they’re absolutely essential for the ski tourer. There’s an electronic CAS product in association with SwissTopo but I’m not really clear what it is and if it covers ski tours or summer routes.. Besides, it’s fun to sit planning routes with the books and maps !

Tip #1 : When transferring the coordinates from the map we’re only looking for way points, the easiest location for waypoints are where your route crosses a grid line on the map, this way you only need to measure on one axis.

Tip #2 : I store each route in a different MapSource file but I start with the same template each time, this template has a series of waypoints stored in it that I’ve entered, for example huts, ski lifts or landmarks like lakes of cliffs etc., along with some I’ve recorded from other trips. This makes planning a route quite quick.

Now I have a MapSource route I can use the MapSource feature to look at it in Google Earth. The first thing I’m looking for is if the straight lines between my waypoints are a problem, i.e. they don’t take me over a vertical drop rather than through a couloir. This really helps with my route visualisation as well, in practice I tend to know the area I’m heading into reasonably well but Google Earth can help me identify some potential risk areas.

So, why did my actual route vary from my planned one? In summer paths are pretty fixed things but in winter it’s not so much the case, snow cover varies each year, obstacles appear like avalanche debris for example and, all things being equal, you’d tend to follow an established track for ascents at least. That means it’s probably not too worthwhile trying to plot an exact route on the GPS, heading the right direction and avoiding the obvious obstacles is good enough. I’d also intended to go to the cabane at Becs de Bosson for a drink and for some reason I can’t recall now decided not to.

What I did need to do was hit my waypoints numbered 90 and 120, I needed to hit number 90 as it was the only realistic point to cross that ridge and there were some significant local risks just at the end of the climb, from there I contoured out instead of dropping straight into waypoint 100 to avoid some potential risk on a 30′ + slope facing into the sun. Likewise, I wanted to hit waypoint 120 to take a decision on a direct line to the barrage on some steeper slopes opposed to the the low risk line I’d plotted into the GPS. I also plotted a line into the GPS to avoid a couple of small cliffs that would have been a risk in poor visibility. The actual track shows me zigzagging a little to avoid those cliffs which was simple enough in the good visibility that day.

The red line showing my actual route then seems to head straight down the valley, in fact the GPS lost the fix leaving the barrage.

This highlights one of the things that annoys me about the unit, there’s an alarm to tell you you’ve lost the fix which is totally inaudible so you don’t realise what’s happened. That’s not to say it’s actually hard to get a fix, my experience tells me that had I stopped at any point on that section of the descent and pointed the GPS at the sky I’d have quickly got a fix. In this case as the avalanche risk in that section was high I didn’t stop until much later when I noticed I’d lost the fix.

Garmin have announced a “high-sensitivity” version of this unit now which might hold onto the fix better, that’s certainly going to help but I’m not so sure it’s necessary. I’ve not found any problem getting a fix in normal use when I stop and consult the GPS or map. The loss of fix doesn’t hamper navigation just the production of the track data, a louder beep would be just fine.

I’m having mixed results with batteries currently and their life. It’s certainly worth carrying a spare set in my experience and even better to be sure you’ve actually got a map and compass, know how to use them and where you are.

Actually moving with the GPS I’ve not encountered any really bad weather so far to test it, I still prefer to glance at the paper version of the map along the route, this is part ritual or habit but the map has some advantages as it lets me see a wider context for location as it’s not limited to the tiny screen on the eTrex Vista. Between the map, my planning and visualisation of the route and my local knowledge of the nearby peaks and mountains I’ve not really had call to to rely on the GPS at all. I’ve used the barometric altimeter as well but again, I generally have a good idea what height I am at and my climb rates, this needs calibrating from a known height each day but seems pretty accurate, it will be interesting to try this more in some more variable weather though.

What is impressive though is that when the navigation is activated features such as “time to next waypoint” are available, this has proved surprisingly accurate and predicted my arrival at the barrage to within a couple of minutes.

Software

I’ve recently made an Apple MacBook Pro my main computer so I’m disappointed that the MapSource application is only available for Windows. As a result I’ve ended up using VMware Fusion to run this and a couple other things under a version of Windows XP. Apple Boot Camp or Parallels would equally support this. Garmin do seem to have plans to get MapSource running on the mac’ according to this blog entry : Mac Betas, obviously this is vaporware at the moment and there’s no indication how existing users would get upgrades etc.

There’s actually several ways to get your track onto a Mac’, Google Earth or LoadMyTracks for example, however they lack some of the features that MapSource has. In MapSource I can edit the track to remove the odd rogue point where the GPS lost accuracy and placed me in a lake or something, I can also filter the track to remove unnecessary points although this is a bit cosmetic, it’s just that if you go in a straight line you get point after point where two would be good enough.

So, I end up using MapSource under Windows XP. I back up the raw file then make any edits I want before saving it as a GPX (GPS eXchange Format) file which is a pretty common format. From here I can go back to the mac and work from there.

I then produce a KML (Keyhole Markup Language) file, this is the format used by Google Earth and lets me post the file on my blog like this :

which obviously need the reader to have Google Earth installed. Another option is to use the web based Google Maps like this :

And of course you can just produce JPEG files in the application as I’ve done above.

I make the KML file using the tool GPSBabel which runs on a variety of platforms including a GUI version for the mac.

Since I never leave home without my camera the next thing I do is “geotag” the photographs, this involves using the track data to place metadata in the photographs about the location they were taken by matching the times. Obviously this sounds like a chore but there’s software to do it. Originally on Windows I’d used the World-Wide Media eXchange client which is simple and easy to use, it’s part of the Microsoft Research so presumably it might find it’s way into their products at some time. On the mac I’ve got the excellent HoudahGeo application, this is a classic mac application; simple and easy to use and looks great.

This does highlight the need to remove those rogue points from the track though, the gecoding applications have to work out where you picture was taken from the time in it and the time on the track, this may or may not correspond to when the GPS actually recorded a waypoint. From here you can put your photographs into Picasa which can show the locations in Google Earth or submit them to a service like Panoramio who submit them to Google Earth. In fact, Panoramio have just been bought by Google so that service may develop. Of course, these photographs will be accurately tagged, if you look in Google Earth there’s some howlingly bad locations entered!

Links

I’ve come across a couple of sites that act a repositories for GPS routes, so far I’ve not posted any track files nor have I used any but these sites look interesting :

GPS-Tour.info

gps-tracks.com

Summary

The eTrex Vista Cx really has four different functions :

• provides location using latitude/longitude or local coordinate system
• shows position on colour map screen
• tracks and stores location for later download
• acts a barometric altimeter.

If you can start to sacrifice features then there’s some cheaper units available from Garmin and others. For instance simple units that really only produce tracks or ones that don’t have maps.

I’m very happy with this unit myself, the single item that annoys me is the inaudible warning when a fix is lost or low battery. In general I’m a bit suspicious of GPS if it’s used as a substitute for reading a map and using a compass, those are vital, in fact essential, skills in the mountains. It’s light and rugged and easy to use in all sorts of light conditions with the aid of the backligh, Garmin suggest these models are focussed on the mountaineer and that’s a reasonable claim for them to make.

This work, unless otherwise expressly stated, is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 Unported License.

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