GPS: GPS receiver testing – Garmin Dakota 20

[Bryan]

Here are the results of my initial testing with a Garmin Dakota 20 GPS receiver.

First impressions

Before I began any careful testing, I played with the receiver for a while and gathered many favorable impressions. Having had a GPSMap 60CSx for quite a while, I noticed many differences in the Dakota.

Size and weight

The most noticeable difference is the size. The screen size is the same, but the unit is much smaller. It's about the same width and depth, but much shorter (98mm or 4" vs. 161mm or 6.25"). It is also much lighter weight (102 grams or 3.62 ounces vs. 160 grams or 5.64 ounces with memory card and without batteries).

Screen

Having read much about the screen on the Dakota I was pleased to find that it's totally useable. True, it's not as clear as the 60CSx. But I never have any problem reading it in either bright or obstructed daylight. The loss of clarity is the price paid for having a touch screen, which in my opinion is well worth it.

I never use the backlight during normal use in order to conserve battery power, but when using it at night, it is more than adequate.

It's not easy to get a picture that realistically represents the way the screen looks to the eye. This one is a relatively good representation of what it looks like in the direct sunlight, which can be a difficult situation in which to see clearly. The screen is somewhat dirty in this photo, with sunscreen-stained fingerprints, which is typical of how it looks in my normal usage.

Ease of use

In useability, the Dakota is leaps and bounds ahead of the 60CSx. Not only because of the touch screen vs. several different buttons and a directional rocker switch, but also because of a vastly improved user interface. One example of the advantages of the touch screen is the ability to drag maps around instead of having to use the arrow keys. And text entry with a touch screen compared with arrow keys is far faster. An example of the improved UI is having all the settings in one place instead of context menus under each screen.

Satellite acquisition

The HotFix system works very well indeed. Initial satellite lock is extremely fast. Usually the unit has locked onto enough satellites to navigate as soon as it's powered up.

GPX file support

Support for GPX files is great. You can just copy a GPX file to the internal memory or SD card and the waypoints, tracks, and routes contained in the GPX file are read by the GPS unit.

Multiple map files

On the 60CSx, you can only have one map file, named gmapsupp.img. If you want multiple maps, they must be combined into one img file using Mapsource or other software. The Dakota supports multiple img files with any name you like. So I can have on the SD card, for example, a city map and a topo map, and when downloading maps from Mapsource, these maps won't get overwritten.

Custom maps

The recently introduced custom map capability is excellent. I have made maps for testing purposes using satellite images, street maps, and topo maps. They are formatted as jpeg files and contained in Google Earth overlays in KMZ files for use with the Dakota. I have experimented a lot with the size and compession level of the overlays. I must say it's very nice to look at your GPS and see your tracks making their way through satellite images like those found in Google Earth. However, maps with lighter color backgrounds are easier to view (that is, it's easier to see your tracks when they are drawn on a map with a lighter background). Custom maps can be turned off if you want to see the map beneath them. Each custom map can have a drawing order to control which maps are shown on top of which other other maps. This works for standard and custom maps.

Other

Performance – The Dakota feels significantly faster. Maps redraw very quickly, startup times are fast, and menu commands are nearly instant. The unit powers on and is ready to use in under ten seconds.

SDHC card support – The Dakota works flawlessly with my Sandisk 8GB SDHC card, so I will never have to worry about storage capacity for maps. Plus it has 1GB of internal memory.

Profiles – The ability to create different profiles, each with its individual settings, is very useful as opposed to have to change numerous settings for different conditions.

Waypoint editing – Existing waypoints can be moved, renamed, or deleted. You can change their individual symbols too.

Track settings – Long-awaited support for up to 200 individual tracks. You can set the color and the display options for each individual track. You can even make a reversed copy of a track.

Name lengths – Waypoints names can be up to 32 characters. The whole name displays on the map, but shorter names show in various other places like menus and lists. Tracks can be up to 32 characters.

Compass – The compass works extremely well and is not sensitive to the angle of the GPS receiver. The 60CSx must be held in a horizontal position for the compass to work. The compass does not use any battery power unless it's being displayed, so it can be left on all the time.

Simple PC interface – No need to select "Mass storage mode" from the system menu.

World basemap – I had to purchase this separately for the 60CSx. It's included on the Dakota.

Lithium battery support – The Dakota supports lithium batteries, so the battery meter correctly illustates the proportion of remaining charge of lithium batteries. The battery meter on the 60CSx does not go from four bars down to three bars until the batteries are over 98% discharged when using lithium batteries.

Factory support – It's obvious by the custom maps updates, which only apply to the Colorado, Oregon, and Dakota GPs units, that Garmin isn't going to be releasing any more new features for the older GPS units.

Every time I use this GPS it seems I discover several new and interesting features.

Accuracy and sensitivity testing

I tested by placing both the Dakota and my 60CSx together in my backpack and hiking in the woods while recording tracks. Then I compared the tracks from the two receivers. I also tested by comparing the reported accuracy and satellite signal strengths of the two units on the satellites page in various locations and conditions. To summarize the result, the Dakota was not as accurate as the 60CSx. This is not surprising given the size of the antenna on the 60CSx. However, the accuracy of the Dakota in most conditions was within a few meters except for extreme conditions such as indoor use. There were some circumstances where the Dakota was not able to connect to satellites but the 60CSx could. For normal outdoor use I do not expect this to be an issue.

Track log testing

To test track logging intervals, I logged my track while walking a winding, one-mile route with varying amounts of tree cover. Here are the results. I was happy to find that the intervals have a slightly greater spread than the 60CSx track logging intervals.

Most often setting: 5 seconds average interval
More often setting: 7 seconds average interval
Normal setting: 9 seconds average interval
Less often setting: 10 seconds average interval
Least often setting: 11 seconds average interval

Like the 60CSx, I concluded that the least often setting is adequate for hiking use.

What's disappointing is that the Dakota cannot be set to save track logs to the SD card and also does not automatically save a daily track log at midnight. Hopefully this will be changed in a future firmware release. For now, it's necessary to save track logs manually if you want daily logs. Fortunately, this step no longer performs data reduction like it did on the 60CSx so the complete track log including elevation data is saved. When you save manually, you have the option of clearing the current track log, so the next manually saved track log will start where the previous one leaves off.

Battery life testing

I tested by logging a track with the unit stationary and indoors. The logging method was set to auto and the frequency was set to least often. The compass was off, WAAS was off, backlight was off, altimeter was on, and battery saver was on. I operated the unit occasionally during testing, zooming and panning the map and so forth as well as occasionally powering the receiver off and then back on.

Energizer Alkaline batteries lasted for 20 hours 40 minutes.
Energizer Advanced Lithium batteries lasted for 34 hours 17 minutes.
Energizer Ultimate Lithium batteries lasted for 33 hours 45 minutes. This is about 84% of the time they lasted in the 60CSx.
Conditioned Eneloop rechargeable NiMH batteries lasted for 19 hours 22 minutes.
Conditioned Sanyo 2700 mAh rechargeable NiMH lasted for 25 hours 0 minutes.

Conclusion

I like this GPS receiver! Its smaller size and weight are my favorite features. I like the custom map feature, the easy touch screen interface, the increased track capacities, and lots of other improvements. The downsides are reduced battery life, slightly reduced screen clarity, and less friendly track logging features.

[chinoook]

Thank you very much for the detailed review. Different from many other tests you give exactly the information about usability we need for our work.
I strongly consider to buy a Dakota as well as an Oregon. Based on your test I know they will both do a good job for me.
I was surprised to see that the accuracy fo the Dakota (Sirf III) is lower than on your older 76 device.

I am still discussing with myself to buy one of the two Garmins or to buy the _much_ better designed TwoNav Aventura. I think it could be of great help to carry the whole east Hebei part of our map with us (towers as well as paths) to check all of them and to improve our map right in the field (It is possible to have the whole map of all walls on the device since it does not have the absolute unnatural limitations of the Garmins).
The only drawbacks are the battery consumption (I am having this currently checked) and the price (about three times of the Dakota) and the fiddly AA battery adapter.


-chinoook

[Bryan]

Originally Posted by chinoook

I strongly consider to buy a Dakota as well as an Oregon. Based on your test I know they will both do a good job for me.

I think you'd find the battery life on the Oregon is significantly less than the Dakota. I haven't tested one, but that's what I understand from reading other Websites. I also understand that the lower resolution of the Dakota screen actually improves visibility.

Originally Posted by chinoook

I was surprised to see that the accuracy fo the Dakota (Sirf III) is lower than on your older 76 device.

In general, I would say that the Dakota is more accurate in an open location (e.g. The Great Wall) and less accurate in an obstructed location (e.g. Appalachian Trail). I guess it's due to the antenna design being better (bigger) on the 60CSx.

I hope the Aventura turns out to have much better battery life than I think it has.

[chinoook]

Originally Posted by Bryan

I hope the Aventura turns out to have much better battery life than I think it has.

I read it has 10-20 hours batttery life. Assuming it is 20 hours with lithium batteries I needed 50 for the whole trip, being 0.6 kg which seems ok to me.
The advantage of carrying all our GE knowledge with us seems to be a decisive advantage, since our goal is to document the whole eastern Hebei Great Wall much more precise then ever done.


-chinoook

[Kim]

I suddenly find this test very useful

It seems that the Dakota 20 would be a much better buy than the 60CXs?

[Bryan]

Originally Posted by Kim

I suddenly find this test very useful

It seems that the Dakota 20 would be a much better buy than the 60CXs?

I can answer this question with a question. Would you be interested in my 60CSx before it collects too much dust?

[Kim]

Originally Posted by Bryan

I can answer this question with a question. Would you be interested in my 60CSx before it collects too much dust?

I can only say that I have been more than satisfied with my old 60 CSx. I did the job I needed it to to do - maybe not much more than that, but it did it pretty well. But I must admit that the Dakota 20 is a tempting offer.

[Bryan]

I decided to use Energizer Advanced Lithium batteries to test the compass. I found that the compass can be left on and no extra power is consumed as long as the compass isn't displayed. This is useful because if you want to use the compass, you just select it. There's no need to go into setup and enable it first and then make sure you remember to turn if back off when you're done with it.

But what really surprised me was that the Advanced Lithium batteries lasted for 34 hours and 17 minutes. This is longer than the time I got from the Energizer Ultimate Lithium batteries, which lasted for 33 hours and 45 minutes, but are supposed to have more power. I assume that this is the results of settings I have made while getting to know this receiver better. For this reason, I'm going to test the Ultimate Lithium batteries again starting tomorrow.

[Bryan]

Once again I tested Energizer Ultimate Lithium batteries, and this time they lasted for 33 hours and 39 minutes. Amazing to me that Energizer Advanced Lithium batteries last about 30 minutes longer than Energizer Ultimate Lithium batteries.

The only clue I could find is the difference in max continuous discharge rates: 1.5 amps for the Advanced Lithium batteries and 2 amps for the Ultimate Lithium batteries. This doesn't really make sense because the GPS should use a much lower current than that, but it's the only difference I could find.

[chinoook]

How do you test the battery life of the receiver? How do you know when the device turns off?


-chinoook