This from Lucy Dablin: Garmin 60 CSX is the best. The new models have good reception but annoyingly are not as good!

In GA, some coworkers showed me how to use an Ipad with Avenza software.  As semiretired, I am not affording much.  This has worked well in a couple times I have used it with the ipad 4 that I bought, but it even worked with my ipad 1, but I would not suggest that.  It did well on road stream crossings and tracked a decommissioned road under a canopy and hilly area under a canopy with no issues.  I did this also not connected to a data service, just the ipad locator.  For a large job in one vicinity, you might try a temporary tower with microwave or other locator to correct to, but that technology I have heard about, but don't know the specifics.  With the Avenza, when you upload your exported georeferenced map (such as Lidar DEM hillshade of ground surface) out of Arcmap, bring file up on the Ipad, and the dot will follow your location, pretty close in my experience and may be a way to correct the dot if it is uniformly off.

Where do you plan on using this?  We had a couple different models in Costa Rica and found that reception varied more based on the topography than across the models themselves. 

Thanks for the answers so far... We work in remote East African dry and moist forests both in open valleys and steep terrain. Really needs to be a tough handheld unit rather than an iPad (although I do sometimes use a waterproofed iPad for data entry in the field).

I have both 60CSX and 64ST, they both work well under forest canopy in East African cloud forests (Nyiru, Mathews, Karissia), however 60CSX is faster and its built-in compass is much more responsive than that of 64ST. Avoid Garmin Etrex (all models) they often take very long times to get the signal under forest canopy.

Thanks Luca. How frustrating that a higher model number doesn't correspond to a more improved reception! Dylan, what models have worked under Costa Rican forest canopy?

Unfortunately the quality of more recent Garmin units is lower than the older ones. When I buy a GPS next time I will look for other brands - by the way, does anyone have advice on the best GPS brands to buy, e.g. Trimble? Magellan?

Luca, I have only used Garmin, but with the declining reception in recent models and aforementioned battery terminal problems I would also be keen to experiment.

I have used that one, too. Garmin 60CSX. I have it since many years and still works a treat.

I have used a Garmin 64 in the dense forests of Gabon last year, and it worked very well. It was also fast in getting a reading.

Agree fully with Lucy Dablin and others above: Garmin 60CSx works best under forest canopy. New models do not work as well. 

And this from Debbie Martyr working in Sumatra: We're Garmin 60 folks too.

Andy, we've been using the Garmin GPSMap 62s in mountainous and forested situations in Taiwan and elsewhere without problems.  We found it loads better than all of the other units that we have when used under a canopy.  Hope all's well.  Al

More from Debbie Martyr: [Garmin map64] is ok but not as good as the 60 series.

So the 64 and 62s also look okay (despite my field team's problems with the 64) - thanks Jan and Al... and to everyone praising the 60 series - those were the glory days it seems!

Perhaps you can try the GPS called SOUTH S760. According to our experience, this device could receive the signals well and locating in high precision in complex conditions. 

SOUTH S760 looks promising, thanks Siyuan, although looking around online it seems tough to buy here in the UK.

Yes, I have the 60CSx and it works rather well, +-4 to 8 m.  But sometimes it acts up and drifts about +-10 m or so.  I have read that this can be caused by increases in sunspot activity. on some days. Anyone know about this?

I've used GPS60, 62 and 64 alongside eachother at several Borneo sites and the newer models keep the signal much better - especially in dense forest and rugged areas. I heard GLONASS capabilities (in the 64) , can be a little patchy across the world, and sometimes are closed to public use, but not sure whether it's true. I'll always get a good fix in an open area first and then venture under the canopy. The 64 will hold a signal consistently for km, whereas the others drop to two satellites, and thus lower accuracy, fairly quickly. Maybe some georgaphic variation??

Matthew now that's what this discussion needed, thanks! The rest of us can't truly compare devices without constant conditions. My team has mostly been trialling the 64 in the wet season so maybe just cloud has messed things up (?). Although others above have also struggled in East Africa and South America...

 Why not try GERMIN 76 csx.

My GPSMAP 60CSX works well under the canopy at Khao Yai, with +-4-8 m.  However, on some days the cursor drifts around +-10 m or so. I have read that this may be caused by high sunspot activity.  Anyone experience this?

Mohammed, I haven't heard from any researchers using the 70 series, but a quick check online suggests that they have already been discontinued by Garmin (they don't even appear to sell them on their own website). I may be wrong. And Warren, thanks for some more quantitative confirmation of the 60csx capabilities. The geek in me now certainly wants to repeat Matthew's trial with the three models at our study site. I'll post something here if I actually get round to doing that.

For mapping in forest I use Garmin GLO logger wearing it on my cap. It is small, lightweight, battery life enough for 10 hrs work. Precision is good as it works with GPS and GLONASS, so you have enough of satellites. Data are transmitted to my cellphone via Bluetooth, where I use Bluetooth GPS for management of connection and other apps for mapping.

https://play.google.com/store/apps/details?id=googoo.android.btgps&hl=cs

If you will need something more rugged, see for example Algiz 10X from Handheld. They have U-block GPS chip set inside, which seems to be very good and precise.

http://www.handheldgroup.com/rugged-computer/tablets-notebooks/algiz-10x/

Thanks Ludek - that's a nice development from the standard handhelds!

As far as I know the Map 60 Csx was the best GPS I've used in very dense canopy cover (rain forest). The 62 is good, but to transfer the files to GIS I had to go from many software until GIS reads it. I think it is good to evaluate how dense is the canopy cover because what works in not so dense cover does not work well in the rain forest.

Hello Andrew, We are using Garmin 60 and 64 with Duracell batteries in the dense canopy forest in  Cameroon. For 14 days monitoring recording our track (from 7 am to 3 pm) we average use 3 pairs of duracell batteries. Hope this help

Andrea and Daniel, thanks! While the later Garmin models aren't without their problems it seems they should really be doing the job. This from the Garmin website (regarding 64 series): "... locates your position quickly and precisely and maintains its location even in thick forest and deep valleys."

hahahahha I think Garmin should ask us to test the GPSs before post any information... thick forest can be secondary vegetation that are not tall, and deep valleys with no trees, yes, even the Etrex works well :))))

Good point Andrea (!), and note that the Garmin quote doesn't actually state that the 64 series locates a position quickly and precisely in thick forest, rather that it "maintains" the location in thick forest. So this may mean that we all still need to get a signal under open sky before moving into the forest, which is what my field team has been reporting.

... but then this discussion all just academic if we keep losing forests at the current rate. It's ironic that degraded forests are easier to ground-truth than closed canopy, and yet maps of forest degradation are mostly quite inaccurate.

Hi Andrew,

You are right, there are so many critical points that should be considered when mapping vegetation structures. I like to think that people do the best they can, but sometimes seems that the maps don't  really show what is happening in degraded places.

I prefer to use Trimble on that case,  specially the new version.

OK, I am outnumbered.  I know the Garmin and Trimble are really made for this use, but they cost a lot more.  I have no idea if what I suggested might work for you or others.  I also understand the Ipad is clunky to carry in the field and I had to buy a waterproof protector case, vest with big pocket, etc.  Still my total investment was less than $400 since I bought the Ipad 4 and the protector on sale, and I had access to Arcmap with full array of GIS coverages already for the places I work.  For the casual researcher on a budget where you have access to the GIS already, or if you have an Ipad or Iphone, (likely works also with Android cell phone), access to ArcMap or probably Google Earth may work for some, just download the free Avenza download, store a few georeferenced GIS maps and try it out.  There are a few things to learn, but not many steps.  I think there are several papers on this use out in Western US for firefighting in remote areas.  I have no idea if the Ipad locator works just as well in Africa or other areas of the world.  But with my pdf maps stored on my Ipad, I can pull up any area or any GIS coverage I want that I have stored, and whether it is the LiDAR shaded relief, topographic map with contours, aerial photo, soils layer, administrative map, etc., I can pull it up.  If nothing else, if you carry an Iphone anyway, try Avenza out as a backup.  It would be interesting to find out what you think.  I added one of the links to the USFS use for firefighting in remote areas.  It probably will not do everything you want, but if you are not getting anything due to tree canopies, satellites in wrong position, etc., believe me, I have been there, so I think its worth a try -- it has worked for me in my limited trials.

http://www.marketwired.com/press-release/united-states-forest-service-deploys-the-avenza-pdf-maps-app-for-fire-fighting-2067443.htm

In Malaysia, I love to work with Garmin 60CSX. The best model I proposed. Compare to new/latest model from Garmin, I think 60CSX the best. But now it is not easy to buy this model

You know what William, based on your enthusiasm I will actually give that a go at some point. However, my usage is mostly while walking in thick, mountainous forest with few trails, so a handheld that can be latched onto a belt is much more versatile. And thanks Mohd for another endorsement of the 60csx - someone needs to write to Garmin to ask them to make some more it seems!

You might find something useful on our Whitehall Forest GPS Test Site website...

http://warnell.forestry.uga.edu/Warnell/Bettinger/GPS/index.html

There are some very handy papers on your site Pete, thanks! I see that one of these tests the Garmin 60c and eTrex, but do you know of any papers testing the Garmin 62 or 64 series?

Hi, I can only agree with previous answers: in my experience, the Garmin 60csx works best in mountainous forest (Austrian Alps) compared to other devices I have seen in the field (eTrex, mobile phones, tablets,...). The big rubbery buttons make it easy to use even with gloves and in the rain (as compared to Garmin's newer models with touchscreen), and the protruding antenna seems to give it an edge in terms of reception over other devices. Admittedly, there are good-looking devices from less common manufacturers that I have not seen in the field myself.

The handheld GPS to work, but the coordinates will likely have higher errors than in clean area. Regardless of the type of GPS, we always need to be careful when we use under forest canopy.

The decision to use or not this type of equipment will depend on the purpose of the work. The GPS is a very practical and easy to use equipment, but we need to know and be clear about the purpose and the desired accuracy to make the decision on whether or not the GPS navigation in certain situations.

Andrew, We are testing the Garmin Map64 now. Maybe next year a paper will be available. It is unfunded research, so it takes a lower priority.

Hi Andrew,

what is the task (points, tracks?) and ~accuracy needed? In our recent study we tested several mid-class smartphones and achieved accuracy applicable for tasks with lower accuracy demands (means ~7.5m under leaf-on and ~5.5m under leaf-off conditions, mid-European mixed forest). Battery life (solvable) and poor antenna could be a problem. Therefore, we are currently testing a low-cost (~90$) Bluetooth receiver connected to smartphone http://www.gns-gmbh.com/index.php?id=233&L=1 . Signal strength and stability is much better and so is the battery life (BT is less consuming than the internal GNSS). However, we do not have the accuracy values yet...

Article Horizontal accuracy and applicability of smartphone GNSS pos...

Really useful previous comments. I am planning some research under forest canopy in Sumatra, and after as accurate GPS precision as possible. Has anybody had any experience with Trimble differential GPS devices under forest canopy? Or could suggest any other high precision GPS devices that work under forest canopy (but possibly don't carry as high a price tag as Trimble)? 

Trimble GPS

regards