Hack 55. Use Your Track Memory as a GPS Base Map

Use your own past traces to provide you with context for street navigation and low-rent GPS maps.

Newer GPS devices come with many megabytes of memory to store base maps. Companies like Garmin and MAPSource (http://mapsource.com/) sell CDs compiled from public domain data and some proprietary data to load onto your Garmin device, providing you with context for where you are: roads, names, places, and often small recommendation databases for local services.

These GPS base maps provide context and help you to navigate, but sometimes they interfere with your own story. And other times, for various reasons, there are no maps for where you are going. You can use your GPS to create your own base map out of your tracklogs and waypoints.

5.11.1. Turn Off Your Base Map to Turn On Your Own Story

Maps tell stories, and the stories that maps tell both reflect and create reality. Our experience of a place is created, or altered, through our interactions with maps. We sit surrounded by our wealth of cartographic data, and we forget ourselves and our own stories in favor of the authority of an external mapmaker.

The base map in your GPS reflects (someone's) reality, but it isn't your story. You build your own story over the course of your travels. Storing tracklogs and setting waypoints provides an amazing amount of context for a mapping display. Try turning off your base maps, or setting the level of detail to the lowest setting. You are then able to fill in a huge amount of detail about the places you have been, based on your experiences and the reminders provided by your waypoints and tracklogs, as shown in Figure 5-26.

Figure 5-26. Using tracklogs as a GPS base map

We live in a phenomenal universe. This means we experience reality strictly through our senses. We don't "see" a river; rather, photons of light bounce off of the river and strike our eyes. We experience the energy of those photons, and our brains construct a reality of the river. In the same way, our experience of a place is limited to the physical phenomena that we experience: the atoms that we inhale and interpret as smells, the waves of energy we interpret as sound, the photons bouncing off of everything around us.

Since we live in a phenomenal universe, then what happens when we see a map? If that map is our first experience of a place, then our personal reality of the place is limited to what we experience from that map, plus whatever inferences we are able to make based on other contexts. For example, if you showed me a map of an "as yet unexplored by me" bit of Mexico that was near to a place I had been, I would automatically and unconsciously create an internal model of that place that included the information from the map and what I know about that part of the country from personal experience, as well as the hearsay of other travelers.

You are your own cartographer!

You might not wish to shell out for MapSource for base maps, or you might be in an area without much digital map coverage: most places outside of North America, Western Europe, and Japan. You might just enjoy the experience of trace-based map autoconstruction. This approach can be particularly fun in the places that you visit often but that are outside of your normal routine.

In the 1950s, the French Situationists realized that we tend to live our lives in ruts. In one study, they tracked the movements of a young lady in Paris over the course of a month. Her Paris was a triangle defined by her apartment, her job, and the studio of her piano teacher. In part out of reaction to this intolerable closing of mental frontiers, they created the idea of the derive as a sort of forced wandering.

Over the course of three visits to conferences in Amsterdam, I built up a comprehensive base map of street coverage of the Eastern side of Amsterdam. The experience led to serendipitous spatial exploration, too; I would decide to traverse smaller streets and take small detours so I could extend my tracklog map further in detail. In Oxford, I managed to create such a map for the center of town in a couple of afternoons. This act of forcing ourselves to engage in a task allows us to engage our goal-seeking instincts while not allowing those goal-seeking behaviors to dominate the experience. We are put into the state of forced wandering, of the derive.

On a GPS track map, especially one taken at walking or cycling pace, you find a context that is at the same level of detail as your life. Waypoints, too, provide landmarks and navigation hints, and a reassuring sense of relative distance. However, it's unusual for GPS units to store and emit timestamps with waypoints; if the temporal aspect of your travels is important to you, then you'll need to correlate your waypoints with your tracklogs after the event.

We have a friend who's collecting a "life track" for his small child, a GPS on the buggy reconstructing a narrative of where the child has been. Another friend publishes his daily life track as a geo-annotated RSS feed.

Be careful with track memory, though, if you subsequently want to download your tracks and use them to animate your journey or to geo-annotate pictures you took at the same time. When a Garmin GPS saves your track, it forgets the timestamp for each point. See [Hack #58] for the lowdown on how Garmin GPS devices store tracks, a "gotcha" that catches every GPS carrier once!

5.11.2. See Also

How can you make use of your track map outside of your own GPS? In [Hack #54], we suggest how you could make your own simple base map to load onto other Garmin devices. [Hack #51] uses the flexible GPSBabel to convert between different, custom GPS data output formats into one that different applications can work with.





Mapping Hacks
Mapping Hacks: Tips & Tools for Electronic Cartography
ISBN: 0596007035
EAN: 2147483647
Year: 2004
Pages: 172
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