when using apps, if you are doing research-quality spatial analysis, it will be important for you to know whether the app is reporting an average or the first reading it gets. I know that several of the hobby-grade GPS units report an average but do not provide an estimate of dispersion (e.g. SE, SD). The Tremble units give you the individual points, then you can dump out the influential outliers and take the average yourself. The advantage here is that if you need 95% CI data, this will allow you to hone in on the point much more accurately. Usually, the outliers are LITERALLY a bird or plan flew over you while recording that individual point, or a key sat went behind a cloud while the other sats are in an less-than-ideal conformation in the sky.
I suspect mos of what I am telling you is much more technical than you really need, but since I don't know for sure your needs, I figure I ought to try to help you out the best I can. These details are ignored frequently in the literature, but a plan flying over while the other sats are in a bad conformation can cause you with a supposedly 1 ft resolution GPS to record the point 10 m or more from its actual location. When you are using a GPS and you notice the unit tells you your waypoint is say 5 m to the north, then you go 5 m to the north and it tells you its now 10 m to the east, then you follow thorugh, and it starts telling you its 5 m to the east, its because of the resolution ability + sat conformation + interference in the atmosphere. IT was always interesting to me when I would average the points that there would be individual points that were plotted way outside the cluster. Those instantaneous readings can be WAY off! :) On Tue, Apr 5, 2016 at 9:17 AM, Trevor Middel <tmid...@gmail.com> wrote: > Merav, > > Another app to try, depending on whether you have access to ArCGIS Online, > is Collector. It's available for Windows 10, Android, and iOS I believe. > It's from ESRI and is full featured, though maybe a little buggy still. It > allows use of custom basemaps, offline editing and synchronization of data > from multiple field crews. Also, I was looking into the accuracy of tablet > and phone based GPS vs consumer grade handheld GPS units and ran across a > few sources which suggested the comparison was quite favourable. I don't > have the references handy but found them relatively quickly using Google. > > We've used Garmin handhelds for years now in the field and have been quite > happy with their durability. I don't like how quickly they seem to retire > and change models, and change interfaces but we've managed to live with > that. We also just acquired a couple of rugged Android tablets from Cedar > Tree (CT7) to use as GPS/data logging devices. So far they seem quite good, > this field season will tell for sure though. They are not far off the price > of a consumer handheld GPS. > http://www.junipersys.com/Juniper-Systems-Rugged-Handheld-Computers/products/Cedar-Products > > Good luck, > > Trevor > > On Tue, Apr 5, 2016 at 7:17 AM, Howard, Tim G (DEC) <tim.how...@dec.ny.gov> > wrote: >> >> Merav, >> The open source app Geopaparazzi can do all those things for you. It is >> Android only so would work on the Nexus, not the iPhone. You can find it in >> the Play Store. >> >> Cheers, >> Tim >> >> > -----Original Message----- >> > From: Ecological Society of America: grants, jobs, news [mailto:ECOLOG- >> > l...@listserv.umd.edu] On Behalf Of Merav Vonshak >> > Sent: Monday, April 04, 2016 6:25 PM >> > To: ECOLOG-L@LISTSERV.UMD.EDU >> > Subject: [ECOLOG-L] GPS recommendations >> > >> > ATTENTION: This email came from an external source. Do not open >> > attachments or click on links from unknown senders or unexpected emails. >> > >> > >> > Hi all, >> > I would greatly appreciate your input on a handheld GPS device. I’m >> > looking >> > for a GPS device that would allow me to navigate to my field sites, >> > including >> > uploading plot locations from Google Earth or ArcGIS and viewing them in >> > the >> > field, over an aerial photo of the site. I will also need to record data >> > points. >> > I’m considering using an iPhone 6 or a Google Nexus 9 device, wondering >> > about the pros and cons of each options and the app I should use in case >> > I >> > choose the iPhone or the Nexus. >> > Thank you! >> > Merav > > -- Malcolm L. McCallum, PHD, REP Link to online CV and portfolio : https://www.visualcv.com/malcolm-mc-callum?access=18A9RYkDGxO “Nothing is more priceless and worthy of preservation than the rich array of animal life with which our country has been blessed. It is a many-faceted treasure, of value to scholars, scientists, and nature lovers alike, and it forms a vital part of the heritage we all share as Americans.” -President Richard Nixon upon signing the Endangered Species Act of 1973 into law. "Peer pressure is designed to contain anyone with a sense of drive" - Allan Nation 1880's: "There's lots of good fish in the sea" W.S. 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