I got tired of my DeLorme Earthmate PN-30. When I got it a couple of years ago, it was hot stuff. People were excited about its potential and DeLorme’s willingness to listen to its users. Unfortunately, Garmin and Magellan quickly introduced new models that had better user interfaces and more features. I also got upset when DeLorme issued a firmware update that, based on my understanding, would prevent the unit from using the maps it shipped with. It would only be able to use new maps if the firmware update was installed.
The Garmin eTrex 20 sounded quite appealing when it came out. It uses GPS plus the Russian GLONASS satellite system. The eTrex 20 can also accept GPX files straight from the computer. Just copy and paste. No need to use software to convert tracks, waypoints, and geocaches like with the DeLorme. The eTrex also uses a standard mini USB cable. I can easily transfer data at home or at work. I don’t have to carry the proprietary DeLorme cable around. The Garmin can also display custom maps, created by registering a raster graphic in Google Earth and copying the exported KMZ file right to the GPS receiver. Garmin also has a good reputation for firmware updates and making improvements to their devices. Since Garmins are widely used, there is also more development for them. I was able to find free topographic maps and OpenStreetMap datasets for Garmins.
I think I had been geocaching less because it wasn’t fun or easy to geocache with the PN-30, or at least not as fun and easy as it was with my old Magellan eXplorist 400. I decided to use a couple of Cabela’s gift cards I have been sitting on for over two years to buy the Garmin eTrex 20. Cabela’s had a sale where you would get a $20 discount if you spent over a certain amount, and I had $45 on the gift cards. I ended up getting a good deal on the eTrex and was finally able to use up those gift cards.
The eTrex 20 has a microSD card slot, so I picked up an 8GB microSD card from Newegg. It was $10 on sale, and there was a $5 rebate on top of that. I got an 8GB Class 10 microSD card for $5. Pretty darned good. I was fairly sure the maps I wanted would fit in 8GB, but I wasn’t sure how much free space would be left. Well, I downloaded OpenStreetMap data from garmin.openstreetmap.nl for the area between Des Moines and Indianapolis, and north to Madison. I also got topo maps from GPSFileDepot for all of Illinois. Once I installed the maps to the microSD card, they only took up a little more than 200MB. The detail of the free maps was impressive, especially the OSM map. To the left is a sample zoomed in on the grounds of a school and park. I actually digitized the sports fields and trails shown on this screenshot from my GPSr. It was so cool to see map data I created being shown on my GPS receiver’s map. My position cursor followed the trail I digitized. It looks like just about everything in OSM is shown on the map.
The DeLorme came with maps, which was a selling point for me. I was worried that I wouldn’t be able to get good maps for the Garmin, and that I might have to shell out some cash. These free maps are better than the DeLorme maps, and I will be able to update them for free whenever they get updated. I could probably download more maps, but I am afraid a large map may result in poor performance on the GPSr. I can turn individual map sets on and off, so perhaps I could put a bunch of maps on the memory card and only have one turned on. Actually, I only have the OSM map turned on because it is prettier than the topo maps. Since Illinois is pretty flat, I have rarely found a topo map useful while out in the field.
There are different profiles on the eTrex 20, like recreation, geocaching, fitness, and automobile. I customized the recreation profile a bit and created a new geocaching profile based on the recreation profile. I took a look at the stock geocaching profile, and it really didn’t seem to do anything special or geocaching-related. Maybe I didn’t dive in deep enough. No big deal. I have the unit’s interface set up the way I want now.
This is the smallest handheld GPS receiver I have owned. I like that it doesn’t take much room in my fanny pack and it is light. I did find buttons a little hard to use with gloves on. But I also had a heck of a time hitting the wrong buttons on the DeLorme while conducting a test with gloves on.
Now for the field testing. As stated earlier, the eTrex 20 can utilize the GPS and GLONASS systems. One supposed benefit of this setup is a faster time for achieving a position fix. I have to say, the eTrex 20 does achieve a position fix quite quickly. It’s pretty cool to see a lock on 23 satellites on the satellite page. I noticed that the DeLorme PN-30 reported a smaller position error, usually hanging around 6ft. The eTrex 20 would be around 10ft. From what I have read online and seen in-person, the DeLormes always report a small position error. Is it really that low? I don’t know. Each manufacturer has its own way of calculating the estimated position error. You can’t really take it as gospel. If it’s a high number, you should take it as a sign of poor reception or poor satellite geometry at that particular moment.
Looking at the early part of one of my tracklogs, the DeLorme’s accuracy was not as good as the Garmin. It took about three minutes for the DeLorme’s track to settle down and not be so different from the Garmin’s. Overall, it looks like the Garmin did a better job of tracking where I really was, but the DeLorme wasn’t bad either. They both were usually within 15ft of where I really was, and both were able to show when I changed lanes while driving. When I walked toward a building, both tracklogs went crazy when the horizon was blocked to my south and east. The Garmin’s tracklog was slightly closer to reality in that situation, but still off by about 30 feet.
For the record, I made sure to have the two GPS receivers use the same track recording options. I used a variety of distance- and time-based track intervals to see which would give me the best track.
I did notice one big difference between the two tracklogs. The Garmin seems to have static navigation active. What this does is it prevents movement from being registered if the GPS receiver is moved only a short distance or at a slow speed. This is intended to keep the track from showing a bunch of wandering when the GPS receiver is actually being kept still. If you look at the two tracks in this Google Earth screenshot, you will see the DeLorme (green) has some wandering in its tracklog whereas the Garmin (orange) did not. This was at a stoplight. The DeLorme recorded some fluctuations in position while the Garmin knew it was stopped and did not record any changes. This static navigation function being enabled can be a good thing, but it can also be a bad thing.
Having static navigation enabled is bad when you are traveling by foot. Sometimes walking isn’t fast enough for the GPS receiver to know it is moving, so the indicated position can get stuck. The GPSr thinks this movement is just some wandering and the static navigation cancels it out. When geocaching, you are moving at low speed, and sometimes you will stop to check out the different hiding places. You want the GPS receiver calculating your position and updating the distance and direction to the geocache at all times. If the static navigation function is active, it ends up causing the compass screen and its readouts to stick. This has been discussed on the Groundspeak geocaching forum. It would be nice if a user could enable or disable static navigation.
This static navigation issue combined with an obscured horizon and fuzzy cache coordinates to drive me nuts at one cache. Check out the tracklog to the right.
When I was looking for this cache, the compass page kept telling me I was 60-80ft away from the cache, and the arrow would rarely change direction. I’d walk 60ft and the distance and direction to the cache wouldn’t change. Sometimes the arrow would change direction and the distance readout would change, but they wouldn’t constantly update as I walked along. I made two large loops around the cache and one smaller loop. At that point, I had given up on the compass page and just tried to walk toward the geocache symbol on the map. On top of the GPSr not updating correctly, the coordinates turned out to be off by about 30 feet. It was so frustrating to be walking all over the hillside while my GPSr screen showed no change in my position or the distance to the cache. Having the distance readout stuck at 60ft sounds like no big deal, but it is a real problem if you don’t know which way to go. Plus the search area is equal to pi * 360 square feet. Good luck searching 1,131 square feet in the woods while you have no idea if your search is centered on the right spot.
The terrain here was steep. The horizon to the south was blocked by the hillside. You can see this in the Google Earth screenshot to the left. Even though the signal may have been blocked by the hillside and the trees, the GPSr should have been able to guide me to the cache coordinates and zero out. The eTrex’s navigation was being sticky. Once I found the cache on my own, the distance readout did start to come down. The sticky navigation/static navigation problem gave me trouble at another cache. I abandoned that search quickly because it wasn’t fun to be wandering around with a GPSr with a stuck or erratic compass page.
I became discouraged when I failed to find some other geocaches. I found one cache where the coordinates were off by about 30 feet. The cache was at the base of a tree, and the coordinates I recorded for the cache matched the tree exactly in Google Earth. So I am fairly confident of the eTrex’s ability to accurately calculate a position. I wonder if the fact my eTrex uses GPS plus GLONASS to determine its position is resulting in me having more accurate coordinates than the cache hiders, who were only using GPS. I remember in the early days of geocaching how some caches were recorded without WAAS corrections, so coordinates could be off a little for people using WAAS-capable receivers. Will the GPS+GLONASS receivers show coordinates that differ from those recorded by GPS receivers that were only using the GPS system? Will the difference be enough to matter in geocaching?
I did one test that can be viewed as somewhat scientific. I 
visited an adjusted National Geodetic Survey benchmark to see how accurate my DeLorme PN-30 and Garmin eTrex 20 were. I entered the benchmark’s coordinates into both receivers and navigated to the benchmark. 
Both GPS receivers actually zeroed out! They showed zero in the distance field for a while. I then moved away from the benchmark and walked back. The distance would decrease, but not zero out. I moved around some more and was able to get each receiver to zero out, but not at the same time.
I spent a few minutes taking photos and staring at the GPSr screens. I then decided to do my final test. I wanted to use each receiver to record coordinates for the benchmark. Simultaneously, I used each receiver to average 100 measurements as I held them above the benchmark. To the right, you can see the map showing the official location of the benchmark and the location of the benchmark as calculated by the DeLorme and Garmin.
The Garmin’s coordinates were closest to the benchmark’s actual coordinates. It was off by only 0.001 minutes of longitude, reporting a position that was 4.54ft west of the benchmark. The DeLorme’s coordinates were off by 9.24ft to the northwest. Advertised accuracy for a consumer-grade recreational handheld GPSr is usually 3 meters or 10 feet in perfect conditions. Both units were well within this range.
I have yet to test the eTrex while bicycling because the weather has not been warm enough. I did purchase a RAM mount for the eTrex and have installed it on my bike. It uses RAM’s diamond-shaped connector, so I was able to use the existing hardware that went with the DeLorme RAM mount on my bike. I just swapped out the actual cradle. I also purchased a screen protector after putting a tiny little scratch on the screen after I dropped the GPSr while geocaching.
I don’t have a good way to test battery life, but the eTrex has done quite well. I have had it on for about four hours while geocaching, maybe two hours recording tracks in the car, and maybe another hour messing with the menus. The battery meter has not dropped below full yet. The eTrex 20 has an advertised battery life of 25 hours.
A lanyard did not come with the eTrex. That was disappointing. The DeLorme came with one. I ended up purchasing a lanyard for the eTrex separately. I guess Garmin figured it was a way to save a bit of money on each unit.
I think I need to read the Garmin’s instruction manual again. The only way I can find to cycle through the various screens is to hit the back button. I want to find out if I can cycle forward by hitting another button.
So far, the Garmin eTrex 20 seems more capable and nicer to use than my DeLorme Earthmate PN-30. All Garmin needs to do is sort out that static navigation problem to make the unit more usable while geocaching.
