Archive for April, 2008

More GPS file tricks

Friday, April 18th, 2008

Here is the process I use for GPS data collection and manipulation.

1. I use GPSMan to transfer data from (and to) my Garmin Geko 201 GPS unit, using a serial connector.

2. I save the data (GPSMan allows me to save all the data together, or to save waypoints and tracks separately – I have very few routes to save, but that is also possible).

3. I export the data in GPX format (exporting waypoints and tracks together is only possible in GPX format, individual types have more export options, but GPX is sufficient for my needs).

4. I use GPSBabel from the command line to convert the GPX to KML file type. KML files can be viewed in Google Earth, Google Maps, and probably other mapping tools as well.

What I just found out is that in the flat text file that GPSMan uses (when the Save option in used) allows to enter comments, simply by using % at the start of the line. So now I can describe the waypoints in details, making it possible to remember what they stand for, which is tough in the Garmin allowed name size (6 alphanumeric uppercase characters).

So for example,

SBRGAS N10 02 07.8 W84 09 41.2 symbol=flag alt=1112.1 GD108:class=|c! GD108:colour=~|Z GD108:attrs=` GD108:depth=QY|c%|_i
GD108:state=|cAA GD108:country=|cAA

Now becomes:
SBRGAS N10 02 07.8 W84 09 41.2 symbol=flag alt=1112.1 GD108:class=|c! GD108:colour=~|Z GD108:attrs=` GD108:depth=QY|c%|_i
GD108:state=|cAA GD108:country=|cAA

% Gasolineria Santa Barbara, on the road to Alajuela

I am going to use this now on all my waypoints files, making them order of magnitude more useflu.

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GPS Data Tricks

Tuesday, April 15th, 2008

GPS data is either points or tracks. A point has a longitude, latitude, altitude and metadata (icon symbol, comment on some units, etc.). A track is a list of individual points taken in a time sequence, so each point has a date/time associated with it, in addition to the lon/lat/alt data.

Here is what my GPS data looks like when saved as a text file: there are waypoints, saved tracks, and the active (track) log. My GPS lets me save intermediate tracks and give each a unique name, so at the end of the day it is possible to have multiple saved tracks as well as the active track log in memory (kind of like HD and RAM).

Each waypoint has a name, which is 6 (uppercase or numeric) characters long. Tracks have a track name, followed by a list of waypoints. If there is a break (loss of contact with the satellite, turned off GPS) it is marked with !TS on an empty line, after which the next point will also have a jump in the time or date. The memory is treated as a special track, with the name ACTIVE LOG and a different display code.

!W:
018 N10 00 34.7 W84 12 31.7 symbol=flag alt=938.8 …
MIGRCN N9 57 23.5 W84 06 50.2 symbol=flag alt=1078.2 …
PRCSMH N9 58 56.7 W84 06 28.2 symbol=flag alt=1118.6 …

!T: SB-MIGRA width=2 colour=#000000 mapbak= GD310:display=|c!
10-Apr-2008 16:39:08 N10 02 09.8 W84 09 33.2 1178.71362305
10-Apr-2008 16:39:27 N10 02 08.2 W84 09 33.0 1177.27172852
10-Apr-2008 16:39:45 N10 02 07.2 W84 09 35.4 1170.06176758
…
…
…

!T: ACTIVE LOG width=2 colour=#8b0000 mapbak= GD310:display=|c”
10-Apr-2008 18:06:19 N9 57 23.4 W84 06 50.1 1078.25585938
10-Apr-2008 18:06:59 N9 57 23.5 W84 06 50.2 1082.58178711

!TS:
12-Apr-2008 20:34:16 N10 02 12.9 W84 09 38.8 1157.08398438
…
…
…

Why is this useful? For two reasons. First, it allows us to consolidate waypoints from multiple sources, simply by combining and editing the files. It also allows us to edit data more easily than on the GPS unit. We can then upload the points to a GPS unit when we need to.

Second, tracks can be manipulated in the same way. It is possible to edit the track name, but what is even more handy, we can make any track become the active log by simply replacing the !T line.

Since the active track is the one displayed on the screen, if you want to take the same exact trip, you simply load the active log into memory, turn it on, and follow the track on the GPS display.

Note: I use a Garmin Geko 201, and use GPSMan on Linux to move data to/from my GPS and save/export it to my hard drive. If you have another GPS, your data may look different, and this may not apply to you. I would love to hear from people using similar tool with different GPS units

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Why I like PmWiki

Tuesday, April 8th, 2008

Those of you who bother to read my GPS wiki site , may know that I use PmWiki as my wiki program. Well, today I get a reminder why I like PmWiki so much – the great community forum and support (plus it works great, too).

I wanted to link to the wiki from my main web site, but was getting error messages when I followed the usual instruction, a php include command. Turns out the usual include only works from within the same directory, and I needed a change directory command first.

The point, though, is not the technical details, but rather that the answer in the forum came within hours from the post, and that the answer came from no other than the author of the program himself. You can’t beat that with a service contract from any source.

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BBQ in the rain

Sunday, April 6th, 2008

So, we and a group of people we know decided to have a BBQ. We thought we could do it at the Guachipelin Pool (Balneario Guachipelin), in Santa Barbara de Heredia, around noon time. Here is a link to the place: – anyway, we did NOT plan on the rainy season to start right at the time we were supposed to be grilling, which it did. Lucky for us, we did not have a grill anyway, so the rain had a minor effect on us.

It is amazing to see how much beer and alcohols the locals can consume when it is raining for an hour. They can compete with your average American any day of the week, and at a much more affordable prices.

Check out the GPS wiki for the location. There is also a walking track to it, but you would have to search for it. I am too lazy to add another link for you.

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Trip to La Garita, Casa de Viñedo

Wednesday, April 2nd, 2008

The time has come to add something different to this blog. Today, I took my GPS with me on a road trip, starting at the Santa Barbara gas station for a fill up, then to Alajuela, in an attempt to go straight to La Garita. Alas, the road was closed for repairs, so we had to take a short detour, then continued on to La Garita.

La Garita is a small town, located between Alajuela and Atenas. It is so stretched out that it is hard to tell where the town center is. Usually, each Costa Rican town has a church, school and park at the center of the city. In La Garita, the school is quite far from the church. La Garita stretches on both side of the road to Atenas, which is heavily traveled by both individuals and large trucks carrying stones, sand, and many other products. On the road is the famous Zoo Ave, and several popular restaurants, including Casa de Viñedo and Fiesta del Maiz (literally House of Vineyards and Corn Festival, respectively). The road connects to the main north-south highway, Highway 1, which goes north from San Jose all the way to Nicaragua.

La Garita has an amazing number of viveros – nurseries – selling plants, trees, shrubs, and every other thing that grows above ground.

Casa de Viñedo is a restaurant and winery, with their own wines, sold on the premises as well as in supermarkets nationally. The wines include red (dry and sweet), white (dry and sweet) and champagne. All taste much better after the 3rd cup. The restaurant menu is pretty varied, and also pretty expensive (relative to Costa Rica). Their flagship is the Filet Mignon, which goes for about $17, but is a tender, juicy, delicious cut of meat that almost melts in your mouth. Wine is about $4 a carafe (2 small glasses). No reservation is required, at least for lunch.

Check out the GPS wiki for coordinates and trail.

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