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Globalsat DG-100 Data Logger
Posté le 08 février 2007 à 17:17:36 par gpspassion.

Globalsat DG-100 SiRFstarIII Data Logger

SiRFstarIII - 3 modes - 60,000 points - "mouse" GPS - 36 hour * runtime

Side views, comes with its own USB cable and note the three logging modes

Several useful accessories, including two powerful 2500mA batteries

The DG-100 comes with a removable belt-clip

The Globalsat DG-100 (see the product page) is the first SiRFstarIII data logger I've had the opportunity to evaluate and is in fact the first data logger to rely on the most powerful GPS chipset available. Many users have been waiting for such a data logger to appear since the first SiRFstarIII receivers came out in early 2005 as they typically get used in unfavourable environments (in a backpack, glove box, clipped to a belt, etc...) so the higher the sensitivity the better. Previous favorites included the SiRFstarII Royaltek RBT-3000 or Delorme BlueLogger that were really Bluetooth GPS receivers with an added data logger feature. Not so with the DG-100.

Let's get this out of the way early in the review, the DG-100 is not Bluetooth capable, so it will not be able to double up as a Bluetooth GPS receiver for a PDA or a Smartphone, it can however be used as "mouse" GPS for a laptop or UMPC. Clearly it would have been nice to have Bluetooth, but that would have meant a more complex, lower battery life and likely more expensive device and when you think of it it's generally nice to have a specialized device that you can operate easily.

The DG-100 looks like a small box and feels quite light. The USB connector (held into place by a small magnet) doubles up as a data link and a battery recharger. A USB extender is bundled in the box as well. It's convenient to be able to rely on USB for all operations and was pleasantly surprised to see that it could recharge the two 2500mAh batteries that power the DG-100. I haven't done full battery timings yet, but based on using it normally, their 20/24 hour claim appears to be reasonable enough. * UPDATED 12/21 : Having now done some more testing, I was able to log data for 36 hours with data points recorded every 15 minutes, so that's much better than announced and might indicate that some power trickling is being done. I will log data every 10 seconds to see if there is an impact.* UPDATED 12/23 : that second test run is done and it logged for 37 hours using up 21% of the memory, so it's safe to say the logging frequency has no impact on overall battery life.

In the back you can screw on a small clip that will let you wear the DG-100 on your belt or clipped to a backpack. It sports an MMCX external connector too, that would come in handy if you need to place it in a spot with no view of the sky.

The DG-100 is the first data logger I've seen that has three (A/B/C/)programmable logging modes that can be switched on the fly. Programming them is easy too with the software interface seen below. You can log by time or distance and set some triggers as well :

In addition, the large round button be used to record a data point, more about that later.

I used the DG-100 on several types of outings, pedestrian, bicycle, car and it acquired the fix and tracked as well as other SiRFstartIII based devices judging first by the blinking green status LED and then after downloading and analyzing the tracks on a PC. It's light enough that you will easily forget about it if you wear it on your belt or put it in your backpack.

I switched between the three A/B/C modes several times and it went on logging normally. Pushing the large round button did not give any particular feedback so I assumed it worked although we'll see below that it's hard to know for sure.

This is the crucial stage for a data logger as recording data is one thing, but turning it into meaningful data is another. The DG-100 comes with the "Globalsat Data Logger PC Utility" that lets you send settings to the DG-100 (see above), download the data and export it and also view the live GPS NMEA stream if you switch to "GMouse mode". The DG-100 uses the standard "Prolific USB to Serial" drivers and you can access the live NMEA stream with any GPS software but make sure you keep it activated in the "PC Utility" and then exit the "PC Utility" before connecting with another program.

pedestrian use - logging once every second

driving- logging every ten meters

Downloading data from the DG-100 is one click away and you can see the results above. You might wonder why there are all these lines on the left and dots on the Google Map on the right, well it turns out the DG-100 splits the logs in sessions of 95 points. I'm not certain whether this is a hardware limitation or not, but it can quickly get confusing while looking at the map and trying to find some specific sessions you recorded, not to mention a specific point you recorded by pushing on the round button. You can select multiple 95 point sessions for viewing on the map and exporting (check the box of the "95 point" files you want to merge and then do \Map\View Points. This will show the points on the map and you can export the merged points in the format you choose with \File\Export), but still, I've suggested that regardless of any hardware limitation, the software should split data by session (A/B or C) and possibly by day. Ideally the could add some date and time filters on top of the speed filter they currently have.

While some analyzing can be done with the Globalsat Utility, you need to be able to export it for further use and the Utility lets you do that with kml, csv, txt and nmea (GPRMC sentences) formats :

Google Earth had no problem opening the kml file, but I find GE to be a bit too CPU hungry so I like to view the tracks in Google Maps using the excellent GPSVisualizer website. Unfortunately it couldn't read the GPRMC only NMEA file so I first had to convert it to gpx with GPSBabel and then open the gpx file.Updated : now working, see details below.

Geotagging - I then tried some geotagging with the trial version of RoboGeo and got abnormal readings using the NMEA file (see below for the reasons), while the GPX file did a bit better but was still off mark, it's possible RoboGeo's "trial version error generator" was at play, but JetPhoto Studio did not fare any better, creating a "Runtime 5" error I was not able to troubleshoot, possibly user error on my part, still it will require some work and I suggested that Globalsat add a .gpx format option to their program to avoid these cumbersome conversion tasks and potential errors.

I've mentioned a few above so I'll sum them up here and add a few more :
  1. It seems there is a 95 point limit by subgroup. I realize it’s a way to limit the size of a log, but it’s difficult for the user to relate to, especially since each subgroup gets it’s “red marker” on Google Maps. If there is a hardware limitation, I think the bundled software should group the data by session and when the A/B/C switch gets changed

  2. A filter for speed is nice, but filters for time would be useful, that would allow for cutting of long logs too

  3. I would limit the red marker for when the waypoint was manually recorded with the button, can that be highlighted in the list too?

  4. The google map window has the whole http header, it would be nicer if we only saw the actual map.

  5. Fix the missing 00's problem (see details below) and I would add a gpx format export. Many programs have a hard time reading NMEA data with RMC only and having the user perform the conversion is an unnecessary burden

  6. Allow for use a USB "mouse" GPS from any GPS software application

  7. implement the SiRF “push to fix” (PTF) mode as was done on the TR-101 Tracker/Phone, I think that would be a great feature to allow for very long logging sessions as the battery life would likely be increased by 3 or 4x. I would have it trigger automatically if the interval is set to 900+ seconds. The way PTF works is by putting the receiver to sleep until a fix is requested and to make that process go faster it downloads fresh ephemeris data every 30 minutes.
All in all an interesting and innovative product as we've come to expect from Globalsat, with the hardware aspects being taken care of at this point, but I think the software side still requires some tweaking to be made more user-friendly and useful. Adding a "push to fix" mode would be a large plus for extended battery life, but more importantly there should be ways of exporting the data to make it immediately usable with other programs, and specifically Geotagging programs as this is likely going to be a target market for this device. The DG-100 is available for about $100.

If you have questions or comments, you can use this thread of the forums.

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