Collect Settings (Required Accuracy/Streaming Interval)

[tonytony]

Can I get a quick overview on what the Required Accuracy means in the Collect Settings? If its at 3m, is it saying that the accuracy will be within 3m? If so then if I increase the accuracy to 24m, then I am saying that I would like the accuracy to be with 24m (less accurate but better chances to actually getting a location) Also is the streaming interval updating the satellite positions ONCE every x amount of seconds defined?

These are entry level questions, I know, just would like a formal explanation.

[RussRoberts]

Required accuracy�??The accuracy that must be obtained by the GPS to add a point. So the accuracy set will be threshold value and you can have value below that threshold.
Streaming interval�??How often a point is added to the feature you are creating. The smaller the time interval, the more detailed the shape.

Cheers
Russ

[GarethMorgan]

Russ,

We've recently started using an external GPS receiver, a Geneq iSXBlue II, which we purchased to enable us to record with sub-metre accuracy when required. I'm wondering how closely the accuracy level shown when collecting features through the app reflects that of external GPS receivers such as the Geneq?

Thanks,
Gareth

[RussRoberts]

There are different limitations between iOS and Android and the location accuracy that is displayed and if the location information is going through the location manager on the OS. Are you using the iOS or Android version of the app? Also here is a helpful blog on some of our tests with different GPS units:http://blogs.esri.com/esri/arcgis/2013/07/15/smartphones-tablets-and-gps-accuracy/

Russ

[MiaogengZhang]

I tested with one external receiver with iOS device. The location manager in iOS device doesn't carry accuracy information from that external receiver to iOS application.

[GarethMorgan]

Russ,

We're using the iOS version of collector on iPad pared with the external GPS receiver. From Miaogang's post it seems that the accuracy level displayed is that of the internal receiver, rather than the external unit, so the features we plot with this setup should be more accurate that the app indicates. Is this a limitation of iOS location manager, rather than the app itself? It would be useful to know a fairly exact figure for location accuracy for some of the work we do using Collector.

Thanks both for your help with this.

Gareth

[PaulFiner]

My suspicion is that the Collector app for iOS (and maybe Android, too; I don't have one) uses a stationary speed filter when it acquires coordinates to prevent measurements from jumping around when the unit is stationary.

I tried this out in the field using a points feature class based map. I put my iPhone 4S on a monumented location and let it settle for a  minute. The location icon changes from a bearing (motion) arrow indicator to a solid blue circle indicating lack of movement. If I collect a series of measurements without moving the phone, the readings all have the exact same coordinates (not very likely based on the inherent repeatibility of GPS). This, I think, is because since the phone hasn't changed location within X meters (whatever is coded in the app), the app considers it stationary and uses the last set of coordinates acquired.

If I collect a measurement on a monumented location, and then move off of it about 10 meters (the location icon shows movement) and then return the phone to the monumented location, let it settle until the stationary icon appears, and collect another measurement, the coordinates are different (like you'd expect).

While I can see the practical aspect of such an arrangement, it makes it difficult to determine the inherent precision and/or accuracy of the system.

Comments?

[MiaogengZhang]

I have tried using the same external GPS. Android will report me around 1-2 meter accuracy while iOS only give me 5m at best. I assume it is the limitation of iOS location manager. But I haven't gotten a chance to confirm with Apple yet.

Russ,

We're using the iOS version of collector on iPad pared with the external GPS receiver. From Miaogang's post it seems that the accuracy level displayed is that of the internal receiver, rather than the external unit, so the features we plot with this setup should be more accurate that the app indicates. Is this a limitation of iOS location manager, rather than the app itself? It would be useful to know a fairly exact figure for location accuracy for some of the work we do using Collector.

Thanks both for your help with this.

Gareth