Malcolm's comments are super important if you are concerned about sub-10m accuracy. By chance I was just lecturing my Wildlife Students today about this very topic. We have always used Trimble (not "Trumble") units with their software (even though both can be ENORMOUSLY irritating,have compatibility issues from one generation to the next, and are sooo non-intuitive) because a) we need sub-meter accuracy & b) we need the unit to be honest about when it can and cannot get real data. Many cheap GPS units (and your phone) will happily give you a position, but as Malcolm says, you have little idea how accurate it might be...
On Tue, Apr 5, 2016 at 12:21 PM, Malcolm McCallum < [email protected]> wrote: > 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 <[email protected]> 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) < > [email protected]> > > 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- > >> > [email protected]] On Behalf Of Merav Vonshak > >> > Sent: Monday, April 04, 2016 6:25 PM > >> > To: [email protected] > >> > 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. Gilbert > 1990's: Many fish stocks depleted due to overfishing, habitat loss, > and pollution. > 2000: Marine reserves, ecosystem restoration, and pollution reduction > MAY help restore populations. > 2022: Soylent Green is People! > > The Seven Blunders of the World (Mohandas Gandhi) > Wealth w/o work > Pleasure w/o conscience > Knowledge w/o character > Commerce w/o morality > Science w/o humanity > Worship w/o sacrifice > Politics w/o principle > > Confidentiality Notice: This e-mail message, including any > attachments, is for the sole use of the intended recipient(s) and may > contain confidential and privileged information. Any unauthorized > review, use, disclosure or distribution is prohibited. If you are not > the intended recipient, please contact the sender by reply e-mail and > destroy all copies of the original message. > -- John Anderson W.H. Drury Professor of Ecology/Natural History College of the Atlantic 105 Eden St Bar Harbor ME 04609
