Hi all, Thank so much to everyone who sent their recommendations! I appreciate the time and effort. I’ve decided to try some of the applications on my iPhone, hoping to avoid buying a GPS device. I might buy an external GPS to get greater precision. Thanks! Merav
Here’s a compilation of the replies I’ve got (there’s some really got stuff in there, including a list of useful applications to choose from - http://colibri-ecology.com/wp-content/uploads/2016/04/mobile-apps-for-wildlife-and-botanical-fieldwork.pdf <http://colibri-ecology.com/wp-content/uploads/2016/04/mobile-apps-for-wildlife-and-botanical-fieldwork.pdf>): Choosing a GPS is not always a simple task. It depends a lot on what you intend to do and the conditions under which you are doing it. Generally, the quality of GPS range from hobbiest to survey-quality devices. For most stuff that does not require exact point accuracy and precision, most of your hand-held garmins, and even some phones and such will do fine. However, if you are needing 95% CI data for each point, you will need to use a much more expensive unit (Say the old Tremble XL or XM). If you require surveyor-quality, you are getting way up there. Now, the side of the box will tell you the precision of the instrument, however, that is the precision under the absolute best situtation when there are no clouds/overcast, the satelites are perfectly distributed in the 4 quadrants of the sky, and you are on a flat plane with no birds, bugs, or planes flying over. This is why I mentioned the 95% CI data. In that case, you would need to collect something like 180 data points at each location to get to 95% CI. You can geocorrect your data using several methods, or you can use a waystation to correct your information. However, for most uses, a GPS is intended for landscape studies and not microscale studies. YOu log the site, then you measure within the site using traditional methods. OF course, you can use the GPS for these microscale measurements, but if you under a lot of tree cover or have a lot of clouds, or yoru sats are in weird positions you will find your data to be fuzzy, but still usable (usually). If you are just trying to get within a stone's throw of your site, then I would just get a basic garmin used by geocachers and such. IF you need higher quality, then its time to talk to the sales people at tremble and find out what suits your needs. I used to have a nice garmin GPS that was also a palm pilot, and it worked pretty nice. ALl the trembles are also handheld computers. However, I am not super-famliar with the new phone GPS as far as how accurate/precise they are. My bet would be not very compared to the actual research-grade unites. I hope this is useful for you to make a decision. —————————————— 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. —————————————— I used the Garmin GPSMap 76. I was able to transfer text files with coordinates to the device and download recorded points. The upgraded version may be even easier to use. It's a decent field GPS. If you are going to be near water, I recommend the waterproof sleeve. You can still use the GPS through the sleeve. —————————————— In my work I use a Garmin Magellan. They are a bit expensive (about $550 or so). I have not uploaded aerial photos to it, but I have imported polygon shape files from ArcGis which has been very helpful. Accuracy is around 3m on my field sites, but of course depends on satellite coverage. If you do get one, I recommend getting a Gizzmo vest to go with it. That’s a protective cover that is sold by a different company. I use my gps in Puerto Rico where I am conducting mongoose research and have uploaded grids of camera locations, trap locations , etc. —————————————— I’m finding fewer and fewer uses for a standalone GPS unit. The internal GPS in smartphones works well enough for nearly all purposes. And when coupled with the right mobile app, the smartphone GPS can outperform most standalone units. I recently compiled a list of mobile mapping and other apps I have found useful for wildlife and botanical fieldwork. That list is available here: http://tinyurl.com/heyqnln <http://tinyurl.com/heyqnln> —————————————— 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 <http://www.junipersys.com/Juniper-Systems-Rugged-Handheld-Computers/products/Cedar-Products> —————————————— I've been using ArcCollector and Google Maps installed on an iPad for fieldwork, and I am pretty satisfied with this setup. I have a wireless GPS receiver connected to the iPad via a Bluetooth connection, and I'm sure you could do the same with an iPhone. I like ArcCollector because it's connected to my ArcGIS Online account--I can log data using ArcCollector in the field, and then my data is uploaded to the cloud when I choose to do so. The only drawback is that I have limited functionality when I am out of cell reception because I can't load my maps (but my GPS receiver still works, allowing me to access my location and altitude in real time). When that happens, I have backup data sheets to use and log into ArcCollector when I am able to use mobile data. I've been using this receiver, which comes with a free app that is available for download: http://gps.dualav.com/explore-by-product/xgps150a/ <http://gps.dualav.com/explore-by-product/xgps150a/> —————————————— I just went through this for my grad project. We decided on running Collector on an IPad mini 4. Theoretically you could run that on a IPhone 6 or a Nexus and use it for data collection as well as navigation but I bet that screen would be small. In the past I have used Trimble Juno 5's that have great accuracy especially with the point averaging enabled and do well under canopy. If you just need rough accuracy (2-4 m) and want a free app check out Trimble's Outdoors App Suite. You might have trouble uploading a lot of points with the free version of the app, but with the paid version (I think I pay them $35 annually) you can upload .gpx files and then send them to your phone. I have used this system for habitat work on private land (hunting lease & cost share) where I needed documentation, but didn't have access to ESRI software or the ability to spend money on a better system and wanted a file I could look at with Google Earth. Also if you need greater accuracy you can use a Bluetooth GPS receiver to increase accuracy over your phone. I don't have any experience with the new ones, but I hear Bad Elf makes a sub meter unit. ——————————————— 1) GPS (Global Positioning System) is a specific set of satellites, from the US. But there's also GLONASS, from Russia, and others are planned for the future, such as GALILEO (Europe) and BeiDou-2/COMPASS (China). The general term for "satellite-based positioning method" is GNSS (Global Navigation Satellite System). The device you buy at a store is a GPS receiver (if it only works with the US GPS system), or a GNSS receiver, if it can access more than one system. I'm not being pedantic, there is practical relevance to this (below). 2) A good rule of thumb is average accuracies of ~15-30m for phones, tablets and simple handheld receivers, ~10-15m for better handheld receivers with good antennas. These use the so called coarse-acquisition code, at the L1 frequency. GNSS receivers that can combine data from more than one system (GPS + GLONASS) are very widespread now, and they will improve these estimates simply by having access to more satellites at any given time. If you need sub 10-meter average accuracy, you'll need "survey grade" receivers that use the L2 carrier frequency (precision code). L2 receiver prices can vary by 2 orders of magnitude depending on several factors. And they usually need an external antenna, which costs extra. If you need sub-meter precision, then you need to use differential GPS (DGPS), where the surveying receiver is corrected by a second, stationary receiver (base receiver) that will quantify the expected error during your survey. There are some subscription services that allow you to use data from their own network of base stations, instead of your own second receiver, such as OmniStar (http://www.omnistar.com/ <http://www.omnistar.com/>). But your receiver must support these technologies. Many governments also have public base stations whose data can be accessed, but they might not have bases near you area of interest. The most important though, is to realize that "differential GPS" means having more than one receiver (to compare differences). I've seen several people bummed from not getting the expected accuracies from their "differential GPS", when they actually have only a single receiver. DGPS is a method, that requires specific receivers for using it, but is not a type of device per se. By the way, RTK (Real Time Kinematic) is a type of DGPS positioning where the correction is done in real time (as opposed to after the survey, a.k.a post-processing). 3) A cheap way to improve the accuracy of a mobile device is to use an external GPS, connected to the phone/tablet (or even a PC) via USB or bluetooth. These units tend to have external/better antennas, which are important for better accuracy. 4) There has been an explosion in sub-US$1k DGPS receiver chips in the market now, mostly aimed at the drone market, but they are transitioning into consumer products as well: http://store.swiftnav.com/s.nl/it.A/id.4734/.f <http://store.swiftnav.com/s.nl/it.A/id.4734/.f> . These are bare chips, that could be could be hooked up to a RasperryPi or Arduino if you're into a DYI solution.Might be an interesting project for an engineering undergrad. But these chips are enabling cheaper consumer products as well: http://bad-elf.com/pages/be-gps-3300-detail <http://bad-elf.com/pages/be-gps-3300-detail> (I have no affiliation or previous experience with this specific product). ——————————————— 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! :) ———————————————— > chips are enabling cheaper consumer products as well: > http://bad-elf.com/pages/be-gps-3300-detail > <http://bad-elf.com/pages/be-gps-3300-detail> (I have no affiliation or > previous experience with this specific product). > Your correction of terminology is much welcomed and correct!!! I was not aware of the chips coming out, that will be a huge advantage for a lot of folks, right? Has to be way cheaper. ———————————————— 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…
