I’ve seen enough demos and presentations of ArcGIS Collector over the past year that I think it’s time to take a more in-depth look into what it has to offer. This may have something to do with our old GeoExplorer finally retiring after 8 years of great service. Do I replace the Geo with a new one running ArcPad or TerraSync? Or do I switch to an ArcGIS Collector based option? Either way, it was time to review some of the more recent GPS options available in the market.
For us, it’s a pretty easy decision based on the user requirements: ArcGIS Collector. However, this isn’t the solution for everyone, and our requirements aren’t exactly typical. We have the infrastructure, Esri licenses, basic field data collection needs, with accuracy requirements ranging from 30cm to 5m. This accuracy range will be discussed in more detail - since it’s the one variable that has lots of options and configurations. So let’s get started with some of our ArcGIS Collector External GPS Options…
When reviewing our ArcGIS Collector External GPS Options, I quickly realized there is an abundance of… options! Too many really. So first things first - back to the requirements and possible use cases. Since we still have other hardware and software that is field worthy (ArcPad, ArcMap, Laptops, Toughbooks), selecting an external GPS that can be leveraged by multiple devices also seems like a good idea. In summary, here are the GPS requirements we ended up with:
- Must have Bluetooth connectivity
- Note: Some GPS device compatibility differs by connection method, the compatibility requirements below are based on Bluetooth only. USB connectivity is a bonus but not required.
- Mobile OS connectivity: iOS and Android
- Desktop OS connectivity: Windows 7/8 for laptop/toughbook use
- Compatible Software: ArcGIS Collector, ArcPad, ArcMap
- Satellite Systems: GPS and GLONASS. We require both systems due to better response under canopy cover (better chance of seeing more satellites).
- Location Protocols: NMEA and Apple protocols (to support software requirements).
- Accuracy (CEP): 30cm to 5m - varies depending on activity.
- Must be attainable in the field without using post-processing afterwards.
- No subscription service. It would definitely help (on-the-fly correction), but due to the vary in seasonal use, and budget constraints, we had to forgo at this point. Not many options either - although I hear Trimble will be releasing something in the near future.
The Apple/Android tablet debate isn’t something I want to get into. Talk to your resident [OS] fanboy for more information. If you have a mobile OS preference - go for it. If you have a company standard - stick with it. Since Apple controls its hardware and a similar Android tablet was more expensive, we ended up selecting Apple’s iPad Air (Cellular + Wi-Fi model). There are many similar Android tablets, but if you want to use the internal GPS, different Android devices have different specs so select with caution. With Apple, you get the GPS chip they provide.
iPad Air Location Services Comparison. Source: Apple (Location Services section). 5m accuracy assumed to be CEP based.
Even the iPad Air has some variation: The cellular version includes a GPS chip, while the Wi-Fi only doesn’t. The cellular version doesn’t require a cell plan for the GPS to work - although the benefit of a cellular plan is that Collector can perform real-time edit updates to your database! The Wi-Fi only model still has “location services”, but this is Wi-Fi/compass based only, and really isn’t a great option for field collection unless you always have an external GPS connected or plan to manually select locations - so it’s not bad; just not as good. With an embedded GPS, the cellular iPad does give us some flexibility to collect data without any additional/external GPS device when location and accuracy permit.
You may have noticed I listed other hardware devices in the requirements section, mainly Windows 7/8. Since we have some field laptops and toughbooks, we require the same external GPS be compatible with these units and software (ArcPad/ArcMap). If someone requires to use their toughbook in the field, we want to be able to provide the same external GPS device (via Bluetooth) - providing consistent accuracy, training, and GPS support regardless of hardware.
ArcGIS Collector External GPS Options
Finally, the part you probably skipped down to read - the ArcGIS Collector External GPS Options. Below are the devices I could get my hands on to review which related to the requirements. No sponsorship, freebies, or web ads determined the device list. Just a helping hand from friends who have the GPS, or if I already had one at work/home. That said, the device list contains most of the popular options available at this point (most are also discussed in GPS/esri forums as well).
*Notes on Accuracy: Most of the GPS devices didn’t specify the measurement accuracy they’re reporting even though they supply an accuracy value. This should be one of the most important statements, but it’s omitted way too often by manufactures and resellers (IMHO).
“Since accuracy is a statistical measure of performance, a statement of navigation system accuracy is meaningless unless it includes a statement of the uncertainty in position that applies.” ~ Navipedia.net
So where the accuracy measurement isn’t stated with the value, I think it’s best to assume Circular Error Probability (CEP) is being reported (50% of the locations have an error lower or equal to the accuracy value). Garmin has a history of reporting with CEP, even though it isn’t mentioned on their website anymore. Similar with Bad Elf products - no mention can be found, so assuming CEP. The DUAL XGPSS160 does communicate their device accuracy as 2.5m CEP. On the high end, Geneq states the accuracy in many variations, including RMS, R95, 2DRMS, and CEP. Thank you DUAL and Geneq for helping and understanding not all accuracy statements are the same!
** Although all 3 Bad Elf products appear nearly identical (except $$), there are some major differences and justifications for the variation in price that just aren’t as apparent from the chart. The BE-GPS-3300 does have the ability to get 10-50cm post processed (“Coming soon via SDK and external apps” ~ Bad Elf website), something that many other devices don’t offer. The accuracy listed in this table is based on how we would use the device based on requirements (real-time with Collector, etc). The BE-GPS3300 1.0m to 2.5m range is based on the website description: ”< 1 meter stationary accuracy with SBAS+PPP” and “2.5 meter accuracy while in motion”. I’m not sure if Collector can take advantage of the 1m listing or not, but 2.5m should be a breeze.
The BE-GPS-2200 (GPS only) modal didn’t meet our GPS+GLONASS requirements but was included in the table since it may help others. My previous tests of GPS vs GPS+GLONASS make me feel confident that the addition of GLONASS is worth the cost.
Although the Garmin Glo has the lowest accuracy of the bunch at 3m, it’s meets all other requirements. We’ve paired this unit with a laptop and toughbook but running ArcPad, and with Collector on an Apple device. Works with all units without issue. There seems to be two different bundles available for the Glo: Includes car charger; or includes belt/hat clip. The clip is also very light and clips to a baseball cap or shoulder strap for maximum visibility.
The Geneq iSXBlue II is the stand-out winner for both price ($3300) and accuracy. It is highly configurable and includes the ability to select which NMEA strings (GPGGA, GPGLL, GPGSA, etc) to enable/disable and at what update rate (1-10Hz). It comes with an external antenna that can clip to an extension rod, baseball hat, etc. The main receiver can be placed in a backpack, or strapped to your belt. The best setup I’ve seen is to have a small backpack with the receiver inside, with a telescopic mounting pole attached with the antenna. Also allows the iPad to be stored in the backpack when not needed. The price is relatively expensive to the other devices listed, but overall this is still a much more cost effective solution compared to the old GeoExplorer at the same specs. However, today’s Geo’s can get down to 1-10cm with real-time correction services. If you need this level of accuracy in your handheld device, check out the latest Trimble (AKA: Cansel in Canada) devices.
This article touches on External GPS options based on a specific set of requirements. If 5m accuracy (CEP) is all you require, you might not need to purchase an external device. If you want 2.5 - 3.0m accuracy (CEP) the Garmin Glo, Bad Elf GPS Pro+, and DUAL XGPS160 are all great choices. For 30cm, the best device will set you back a little more - but it can still be leveraged by all your Bluetooth devices and software. If you need better than 30cm, you shouldn’t be clipping an external GPS to a baseball cap or backpack anyway. Many high-end devices do have Bluetooth capabilities, but not all use the Apple protocol (yet). Overall, there is no perfect device for all situations.
The Bad Elf series has a LCD screen, Datalogger with Barometric Sensor, storage and config options, while the Garmin and DUAL devices are both super light and can clip to a baseball hat with ease (no config also means, it just works).
When working with other laptops/toughbooks, the Bad Elf still requires an iOS device for configuration. If you don’t have access to an iOS device… seriously, who doesn’t know at least one person with an iOS device?! As for Bad Elf and the NMEA protocol: The Bad Elf 2300 does have NMEA GPS Output, but it does state ”USB connectivity to PC or Mac provides streaming NMEA GPS data”. Again, not a show stopper, but I’m assuming this means NMEA isn’t available via Bluetooth to PC/Mac directly. Also means it wouldn’t pass our specific requirements. If you don’t need Bluetooth connectivity to a toughbook/laptop with NMEA, this shouldn’t be a concern.
Higher accuracy will cost you - but a real benefit is that external GPS devices can be paired with many different OS/software depending on the need. If 30-100cm is your goal, the Geneq iSXBlue is a great all-around option. But remember, the Bad Elf might also meet your needs at the 1m level (again, unconfirmed if Collector can leverage this spec).
On the lower end, I still recommend an external GPS to pair with your iPad. It seems like you are only getting a little additional accuracy, but remember the location of the GPS. If you are holding the iPad close to your body, you are blocking more satellites. Having a tiny GPS on a hat or backpack increases your chances to see more satellites - and if canopy cover is an issue for you as it is me, we need all the help we can get.