Results tagged “GPS” from I, Curtis

Yesterday (February 29, 2008), I attempted a new trail, Rocktop. It is a 1.5 mile strenuous trail that is mostly upward with many hazards associated with mountain climbing. The trail is quite nice. On Pinnacle you can only see the mountain ahead of you and the trees that you have already passed, but on Rocktop you get many opportunities for some very nice views as you ascend the mountain. At about the middle of the trail you can see the radio and other communication towers that are located at the peak. That is where the hike ended for me. I have for a long time had a fear of heights. This fear occurs only when I can see the ground below me through a straight line descending down, such as while hiking up a trail without many curves (Rocktop). While I turned back this time, next time I intend to take the trail all the way to the top.

And now for some GPS data....

The overall trail. The trail to the west of the road is the first half of Crowders trail. Once crossing the road there is an option, continue on Crowders (a less rocky, but more winding trail to no where... ) or go to the right and head up Rocktop. On this map, everything highlighted to the east of the road is Rocktop.

This is an elevation profile like the one in my previous post. It shows with its curve and with color, the level of height

Here is a new way to look at it, it is overlayed on the same map as the usual Google Earth maps. The altitude is shown in varying colors, indicated by the key on the side.

This is a speed profile that shows how fast (or slow) I was going during the hike. Obviously, as the hills become more steep, I became more sluggish. There are also a few points during which I stopped to take a break.

If you are interested in all of the details of the hike, they are located at http://www.livecurt.net/gps/20080229.html.

Now that I have had a little more time to play with the data obtained during my hike on Monday, I have found a few tools that will allow me to show interesting things from the tracklogs. One of my favorite things so far is the elevation profile, which shows the change in elevation during the hike. This isn't likely to be something that I generate for every tracklog, since most of them are either flat and boring, or they are on such a tiny scale that every mild incline looks like a mountain (they look like an EKG, which doesn't show a balanced or sensible geographic profile). The thumbnail of my first elevation profile is below. As always on my blog, click the image to see it big.

King's Pinnacle

I am a bit fatigued at the moment (woke at around 3am and then went for a hike), so I am just going to let the GPS explain everything: [click me]

This is a sample of a tracklog being overlayed on a map, using Google Earth. This shows the best and worst of the GPS system. First of all, it provides a nice clear shape of where you travel. The trouble begins when the device records a bogus point in its log. When you see sporadic lines and lines that look like they should be the same, but aren't, thats what has happened. In this map, the best example of this is at the top of the map where the device was on its return path to the park office parking lot. Those lines should overlap, or at least parallel, but on the reverse trip something went wrong, data bounced off of a cloud or some other interference "bounced" the signal, placing some of the trackpoints in locations where I didn't travel.

Another use for the GPS tracklock is geotagging. GeoTagging uses a digital or encoding film camera's internal clock stamp on images in the EXIF data format and the tracklog from a GPS (automatically using known time information) to match points in the GPS to images. A lot of modern utilities, including Google's Picasa (with Google Earth), can automatically associate the information in the log with the information the camera writes. The end result is an image that looks no different from before, but includes very detailed information in its attached EXIF data that will allow you to know exactly when and where a picture occurred. It may seem trivial to have that information in a picture, but when you think about it, photographs are very vague. A two dimensional rendering of a space doesn't provide for many clues when it has been many years since a picture was taken. Every blade of grass looks like every other blade of grass, and environments change.

I have yet to take any pictures or store any tracklogs of any significance to try this yet, but I will attempt to do so as soon as the proper situation presents itself.

The most useful feature of my new GPS unit is the ability to record and transfer tracklogs. Tracklogs are a GPS-friendly way of making a note of each piece of data they create when reading their latitude, longitude, altitude and time. There are several ways this information can be recorded. Magellan uses a standard non-friendly tracklog format. In this format a line of the track may look like this: "$PMGNTRK,3517.403,N,08115.616,W,00245,M,064603.68,A,,140208*6C". Not many utilities outside of the Magellan platform will read/use this format. A more "universal" tracklog format is GPX, a format that uses XML to record the information. GPX is a native Garmin format. This format looks a bit like this:

<trkpt lat="35.290050000" lon="-81.260266667">
      <ele>245.00</ele>
      <time>2008-02-14T06:46:04Z</time>
</trkpt>

This format is very easy to read, but not many devices outside of a Garmin will use it by default. Now, once I get the information converted (currently performed by GeoVisu v.4) I can use the format in any number of applications. Most of the applications I have found DO NOT support using a background map, only a plotting of points... well... I have a TI-83Plus or a TI-89 Titanium that will do that... so we move on to the next step... see what Google can do for me. Google Earth is an application I have avoided for years, because I used to hate it. Google Earth now seems to be ok, so im currently using it to interpret my tracklogs (from GPX format). Another utility I have found that is somewhat useful is called TrailGauge. It uses US Geological Survey and TerraServer data to create a map of the points in the tracklog, but it is very slow and produces maps that aren't very useful initially, also it is restricted to using about 30km of data at a time... which sucks for longer trips.

I am currently considering training GITI to perform the Magellan TrackLog to GPX Log conversion and perhaps keep a record of all of my tracklogs, but thats a feature for when I have a stronger understanding of the type of data I am working with. I will likely use Google Maps for now for my vehicular trips and TrailGauge for my hiking trips.

There are also some important questions I would love to have answers to:
1. What the hell is GeoCaching?
2. What do sane people do with tracklog data?
3. Are there any good maps availible of state parks that I can use?