Holux vs. Garmin GPS Tracker Comparison

Introduction

Summer 2007 I bought a Garmin-etrex handheld GPS unit. I was happy about its reduced price, I did not know the new, high sensitivity version "etrex-h" would be available soon.

In general I was satisfied with this GPS, but its drawbacks were discovered soon. The most annoying among these was the receiver's low sensitivity. While on the sail course it performed perfectly, the bike trip was recorded less satisfactory. The performance was also very variable in the mountains. The Garmin-etrex practically stops receiving in the forest, its receiver does not find any GPS satellites. This was the reason I started to search for a substitute.

The popular German computer magazine "c't" published a test about simple GPS loggers (in German). The Holux M-241 was a special case among simple loggers as it also contains a display and shows the position and altitude in real time. Thus it is on the halfway between a simple GPS logger and a handheld GPS unit. Both the magazine article and the Internet reports promised better GPS receiving features than the Garmin-etrex. Thus I purchased a Holux M-241, it came with the firmware version V1.11/V02.

Comparisons

I made a comparison between the Garmin-etrex and the Holux M-241 on two mountain hiking trips. The first one was in the French Alps, to the peak of Pointe Droite (2503m altitide, 8212 feet), from there to the pass of "Pas au Taureau" (2555m altitide, 8353 feet) and down to the valley.

The second trip was in the Jura mountains, behind Geneva. This was a short walk from the parking of Tiocan (865m altitude, 2838 feet) to the peaks "Reculet" and "Cret de la Neige" (both 1717m high 5633 feet).

Preparations

The Garmin-etrex performs well in horizontal position. It should never hang down or remain in a vertical pocket. When hiking the optimal place for it is the top cover pocket of the backpack. This remains usually horizontal. For short trips without a backpack or bike tours it is sometimes difficult to find a good place. If you want to watch it during biking you need a special support.

The Holux logger, however, needs to remain in vertical position for the best performance. It can hang down or remain fixed in a side pocket of the backpack. Remember, it is not waterproof, a plasic bag can help.

The first trip

In the first comparison trip we started from a car park in the forest near Samoëns in the French Alps. I already tested the Garmin-etrex in this area and knew it performed poorly in the forest. In addition the first part of the trip started in a narrow valley with high rock walls on both sides where the GPS receivers easily loose connection to the satellites.

As you can see on the recorded map the two loggers performed here differently. The Garmin-etrex often lost the conncetion and recorded nothing. A few times it recorded a total false position, far from the actual track, actually somewhere in the rock wall. The Holux M-241 had better reception, performed better in the forest. On the other hand its logged positions are often totally false, randomly in all possible directions. This way it created a track that is zigzagging in both sides. As a result the full track length recorded by the Holux was some 6.5km (4 miles) longer than the track recorded by the Garmin.

Later on the valley opened up, we arrived an altitude where no more trees were growing and in this environment both units performed similarly. The difference between the tracks remains less than 10-15 meters.

Another picture can be seen on the altitude profile. The shape seems to be similar, except for the first part with poor GPS reception. Here the track seems to be simply longer. But comparing both diagrams the altitude difference is remarkable. The first peak is the peak of Pointe Droite which is 2503m high according the cartographic map. Garmin-etrex measured this 2507m, just 4m higher. The Holux M-241, however, measured 2555m altitude, a major difference. The next peak shows the pass "Pas au Taureau", 2555m according to the map. Garmin measured here 2543m, 12m less. The Holux calculated 2593m, 38m more. This is probably not a result of reception problems, as the elevation plot from Holux data is smoother, while the Garmin plot clearly shows missing points, where the plot is substituted by a straight line.

The second trip

The second trip was a shorter walk to the Reculet and the Cret de la Neige, both highest mountains of the Jura mountains in France, just a few kilometers from Geneva/Switzerland. The walk started from the car park called Tiocan in an altitude of some 865 meters and ascended steeply to the peak of Reculet and to the just few kilometers apart lying Cret de la Neige, both 1717 meters (5633 feet) high.

The beginning of the trip was in a forest. Now even Garmin etrex prerformed well here, probablz because this happened November 15th, and the trees have already lost their leaves. Both tracks lie very close, often in coverage. Holux has measured again a longer trip, 11.23km against Garmin's 10.88km. The altitude plots, however, show again basic differences. Garmin etrex measured Reculet 1721m, just 4m higher than the real height. You can also take in account the loggers were in my backpack, some 1.7 meters above the ground level. Holux has calculated 1775m, 58 meters more. Similar on the next peak, the Cret de la Neige. Here again Garmin measured 1723m while Holux calculated 1772m.

Readout and Evaluation

An important part of the DPS logging is to read out and evaluate the logs. There are many data formats in use and many free and open source programs to evaluate. I personally prefer Linux and open source programs, where possible.

Hardware

Garmin-etrex uses a serial port for communication, something that often called today "legacy interface". There are already laptops sold without serial port, but it seems this old standard will be longer living than many hardware manufacturers like. The problem with Garmin comes with the hardware. Probably due to the waterproof housing it contains a special connector, not the usual standard 9p sub-D as you find on most PCs. The corresponding connection cable is hard to find and expensive. I made a connector myself from a piece of PCB material and springing wires but this is surely not a solution for everybody.

The Holux comes with a miniature USB connector and there is a standard cable in the package. Of course this connector is not waterproof.

Readout

The serial connection with Garmin works easily and well. Many free programs both under Windows and Linux can read out track data correctly and allow accessing other internal GPS functions, like uploading waypoints. The readout speed is a bit slow, to read out a few thousand trackpoints one has to expect several minutes.

The Holux readout is a bit more complicated task. Holux uses a spacial USB profile that is not supported natively neither by Windows or Linux. The Holux CDrom contains a special USB-serial driver for Windows and a readout program, also for Windows. It is important to install the driver first. There is no support for Linux and I did not manage to use the special drivers one can find in the Internet. Even the Windows program does not work perfectly, it is not obvious to find out which virtual serial port is used. If you try with a wrong port, the program stops and one has to restart it from scratch.

Evaluation

I used a Linux program "gpsman" to evaluate GPS data. This program reads out Garmin handhelds directly and allows to visualize and manipulate tracks effectively. It is not straightforward when eliminating incorrect trackpoints. In one window the user has to find the weird data entry (too high speed between two points or too big altitude difference) and in another window one can delete the wrong trackpoint. Unfortunately after deleting the trackpoint the numbering changes in the frist list but not in the second one, thus the best way is to work from the list end back towards the start. The second list can be regenerated every time, but it is time consuming. This program handles the most important track data formats, like GPX.

The Holux program does not allow to manipulate track data just reads out and stores tracks. It has, however, a small conversion program that exports in both GPX and Google's KML format. I used GPX export in order to read in into gpsman.

It turned out the Holux GPX track data was a disaster! When investigating it turned out it contained the track twice (!), once as a list of named waypoints, once as a list of named routepoints. But not as trackpoints. The waypoint names were simple series numbers for every single trackpoint in the list.

Unfortunately most visualization programs show also the names on the created maps. If all points have names, you get a map filled up with names, not even the trackpoints are any more visible. The only solution I found was to open the GPX file with an editor, cut out the second part of the list, the routepoints, erase all names from the waypoints and replace the waypoint tags by trackpoint tags. This is not an obvious task, a tracklist might contain 100'000 points, not every editor can handle 500'000 text lines effectively! After this manipulation the GPX file will be correct and comparable with Garmin GPX files.

Conclusions

These two GPS units set different accents, although their usage has many common points. The Holux M-241 is smaller, more handy. Its logging capacity is much higher. With 5s sampling it can log a two week hiking track, if you can charge the batteries every day. The Garmin-etrex is more versatile, it has more features, including waypoint storage and goal seeking. The GPS receiver of the Garmin-etrex is considerably weaker. It simply stops in the forest. In deep alpine valleys both units performed poorly, you can decide what you like better: missing sections or totally out-of-way trackpoints.

The Garmin-etrex is waterproof, this makes it perfect for sailing tours, where the poor tracking in forest area is not a problem. For biking the Holux M-241 seems to be better. For mountaineering none of them seems to be perfect: the Garmin has tracking problems in the forest, the Holux altitude measurement is rather poor. Perhaps this will be solved with a firmware upgrade.

Or a Garmin-etrex-h would be the perfect solution?


I used the Internet service GPSvisualizer for map creation.

This page was updated last time on January 6th, 2009