topic Re: Automatic GPS Averaging in ArcGIS Survey123 Questions

Automatic GPS Averaging

LarryWiebe — Thu, 03 Aug 2017 14:28:53 GMT

Is there a way to start GPS averaging without any user input when the survey is opened? The would ensure that the user always uses the averaging.

Re: Automatic GPS Averaging

JamesTedrick — Thu, 03 Aug 2017 17:02:29 GMT

Hi Larry,

Currently there isn't a way to trigger averaging manually. Can you provide more information on your workflow's averaging requirements?

Re: Automatic GPS Averaging

LarryWiebe — Thu, 03 Aug 2017 18:09:29 GMT

Hi James,

I am setting up gas meter inspections for roughly 250,000 meters over Southern Manitoba. The inspector has a assigned inbox of meters to navigate to. When an inspector gets to the meter, they answer roughly 20 questions about the state of the meter and we would like to take photos (my other question regarding support for photos on inbox based surveys). We are hoping to refine our meter locations and have found that the averaging needs to be used (iPad) to get a position worth using. Currently the inspector will have to press and hold to start the averaging, which is fine, but will get missed knowing the nature of field work and that is where my request came from. Cellular data is ok in the cities, but nonexistent in the rural areas so everything is geared to be disconnected.

Let me know if you want more info…

Thanks,

Larry

Re: Automatic GPS Averaging

JamesTedrick — Thu, 03 Aug 2017 19:48:50 GMT

Thanks Larry,

I was curious on what you were thinking of in terms of the number of location observations needed to get to a point worth using - is it a set number of observations, a requirement that a set accuracy threshold is within range of the average (say, that 5m is within a 95% confidence interval of the mean), or some other metric?

Re: Automatic GPS Averaging

LarryWiebe — Thu, 03 Aug 2017 20:04:08 GMT

Hi James, When it really comes down to it, the inspectors will only be at the location as long as it takes to fill out the survey. Ideally that will take 20-30 seconds which I would like to use to get the best averaged position. There will be inspections where the user is there for only 5-10 seconds. The position being acquired to help refine the meter location within the land parcel, which is currently based on the parcel centroid. So the point is not the focus of the survey, but a very helpful piece of data for the next time an inspection is performed. I deal with the fuzziness of GPS locations all the time and with the iPad 5m is pretty much the best you can expect, but the averaging will help get us to the 5m more of the time in whatever time the inspector occupies the location.

That is a practical metric, but not very mathematical…

Larry

Re: Automatic GPS Averaging

JamesTedrick — Thu, 03 Aug 2017 20:45:53 GMT

Okay, thanks for the info. Aside from using averaging in this way, are you setting the horizontal accuracy requirement for the point (Geopoints—Survey123 for ArcGIS | ArcGIS )? This will automatically continue to collect the location until the accuracy requirement is met.

Re: Automatic GPS Averaging

LarryWiebe — Thu, 03 Aug 2017 20:58:09 GMT

Yes, I have it set to 5, but I prefer an averaged 5 over a spot 5…

Re: Automatic GPS Averaging

Anonymous User — Thu, 10 Aug 2017 11:17:41 GMT

lawiebehydro Do you mind explaining what the difference is here?

Re: Automatic GPS Averaging

LarryWiebe — Thu, 10 Aug 2017 12:48:45 GMT

Hi Tom, most GPS units, especially tablet based units are not as accurate as they may report. A single GPS reading from an iPad that claims to by within 5m by Survey123 has a much higher potential error that an averaged point over 20 or 30 seconds (positions). I do not know the algorithm used in Survey123 to get the horizontal accuracy, if it uses averaging until it get 5 positions within the tolerance I am fine with the option. If it calculates an accuracy on each point and then stops when it hits the first point that falls within tolerance without averaging the points it has been collecting, the position is subject to a poorer absolute accuracy. If someone can comment on the Survey123 horizontal accuracy methodology, that may negate this whole post...

Larry

Re: Automatic GPS Averaging

JamesTedrick — Thu, 10 Aug 2017 18:41:48 GMT

Hi Larry,

Survey123 uses the location information as provided from the operating system's location, including the accuracy information. Depending on the application, you can be receiving a variety of location signals to determine location (Apple's page on Getting the User’s Location shows some of the options)- Survey123 engages the device's actual GPS if present.

Re: Automatic GPS Averaging

RalphBradt1 — Tue, 14 Nov 2017 00:09:18 GMT

I'd also like to be able to always go to waypoint averaging automatically, particularly in mountainous terrain. I've noticed that when using favorite answers, if the phone doesn't have a GPS fix first, the survey will pull in the location from the favorite. If the favorite wouldn't include it's location, it would help, but I'd prefer any increase in accuracy offered by averaging. I've had multiple surveys done that showed up at the favorite's location. Some I've been able to locate by using the EXIF data from the accompanying photo taken at the end of the survey.

Re: Automatic GPS Averaging

AndrewHargreaves2 — Thu, 20 Sep 2018 13:30:09 GMT

Hello James Tedrick‌ / Ismael Chivite‌ / Marika Vertzonis‌

I'm currently testing the beta 3.1.65 release that includes full GNSS metadata capabilities. I have my locational accuracy set to 1ft, and love that Survey123 will ping my GPS receiver until it reaches that threshold then lock in those values. However, what would also be excellent is if GPS Averaging could be initiated without any user input, as Larry Wiebe‌ requests above. Ideally, this may be triggered based on if the survey detects either:

If I detect I'm using an external GPS receiver and I have ${sourceTypy) ='RTK' then I want ${accuracyThreshold} < 1ft.
If i detect I'm using an internal GPS receiver, or my external receiver does not have RTK service, I want averaging to kick-in and my accuracyThreshold = 5ft

Furthermore, is there already some method to capture the number of positions used to capture an averaged location? If so, I can't find any info on how to get it.

I can't emphasize enough how valuable a "fall back" option such as this would be. It would add significant value to the ability of Survey123 to leverage external GPS receivers which commonly require cellular connectivity to get subfoot accuracies. Knowing I could automatically switch to the averaging option (and not have to rely on field crews to do it for me) would be awesome!

I do think I could rig something up through the use of TWO GeoPoints - making one relevant based on the receiver type and/or ${sourceType}. However, that's a major pain as then I need to query two GeoPoints to determine where I get values such as Lat/Long etc.

Re: Automatic GPS Averaging

MarikaVertzonis — Mon, 24 Sep 2018 03:54:01 GMT

yes we agree with you regarding averaging and it is our intention to add the ability for the survey author to specify how many points are to be averaged as a part of the functionalities first full release.

currently averaging only available with the press and hold method and you can not capture the number of positions used.

Re: Automatic GPS Averaging

KendallNorcott — Wed, 16 Nov 2022 23:03:06 GMT

Has anyone found a way to automatically start GPS averaging when using Survey123 yet?

I've been searching the internet for resources and am now following up on this thread. I'm trying to increase accuracy and minimize the number of details our field crews have to remember when using the app to collect data.