Mapping Hacks

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Chapter 6, Mapping on Your Desktop

#71 Turn Your Tracklogs into ESRI Shapefiles

HACK

This map has one problem: tracks are displayed as discrete points. This

gives the resulting maps a faint fairy-tracing appearance. I find the effect

soothing, as it hints of an ambiguity in time and place. The GPS seems to

speak to me, telling me, “Sure, I knew where you were at this moment, and

then at this moment, and on through the day, but between those times, I

don’t know where you were.” It is as though I traveled through a series of

quantum jumps, disregarding intervening space (a trick that those driving

the Nebraska panhandle will find themselves wanting to add to their travel

kits).

See the next hack, “Turn Your Tracklogs into ESRI Shapefiles”

[Hack #71] for a

way to convert the discrete points to lines.

HACK

#71

Turn Your Tracklogs into ESRI Shapefiles Hack #71

Converting your GPS tracklogs into a standard vector format allows you to

import them into any GIS or mapping application automatically.

Once you’ve gotten your GPS tracklogs into GRASS as site data [Hack #70],

something you’ll notice almost right away is that, when you zoom in close,

your tracklog points appear as, well, individual points, and not as the tracks

you might expect. The reason for this hardly needs explanation. Your GPS

receiver’s tracklog is really just a sample of your location over time, rather

than a continuous stream. When you