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Using Catalyst with a web App on iOS platform

  • 1.  Using Catalyst with a web App on iOS platform

    Posted 02-08-2022 08:42

    I work for Duncan Parnell,  together with a customer, we tested Catalyst DA2 antenna (using TMM to activate Catalyst PRECISION subscription) and their own Web App called WebInspect running on an iPad (iOS).

    They wanted to test Catalyst and see the performance together with their Web App


    See notes here below


    Configuration we tried:

    Catalyst DA2 antenna connected via Bluetooth to iPad Pro (iOS 15.2). Trimble Mobile Manager (TMM) installed, On-Demand subscription with centimeter level accuracy activated. Our web application was opened in Safari. Two third-party native apps (GPSCoordinates and GPS Status) were installed to read coordinates from iOS Location Services and verify if they are the same as in TMM.

     Test Results:

    1. After pairing the antenna with iPad, connecting to it via Trimble Mobile Manager (TMM) and activating Catalyst subscription, we were able to see 0.01 m accuracy in TMM.
    2. We also used another Trimble app TerraFlex and saw 0.01 m in there too. This app though was using the DA2 antenna as a source (a sort of direct connection), not Location Services of iOS.
    3. Then we opened Safari and loaded our web application called WebInspect (their own web app), the application showed accuracy around 4 m. The application uses Geolocation API of the browser and supposed to return location from iOS Location Services.
    4. Then we used both third-party native apps mentioned above and checked accuracy they were receiving from the system - both apps there showing accuracy around 4 m.
    5. Then we thought that maybe it's only the accuracy value that was not displayed properly, but the coordinates themselves were accurate. We tested this theory by keeping iPad on the same spot while one of us was walking away with the antenna - the blue dot representing our current position on the map in WebInspect was not moving with the antenna. Actually, even when the antenna was sitting on the same spot, the blue dot was sometimes jumping from side to side around our real location. It seemed like the application was not receiving corrected coordinates either.
    6. We tried the tests above with another iPad provided by Duncan Parnell - result were the same.
    7. Finally, we tried it with Android based Trimble TDC600 Dev Mode was activated on the Android, Mock Location App setting was set to Trimble Mobile Manager, and in Trimble Mobile Manager itself "Sharing" option was ON. And still, neither our WebInspect app opened in Chrome, nor a native app called GPSCoordinates were able to show precise coordinates - both there showing accuracy around 4 m. We didn't have much time to troubleshoot the issue on Android though.   



    Based on the fact that 1 web app and 2 native apps which normally display location from iOS Location Services were showing accuracy around 4 m instead of 0.01 m that Trimble Mobile Manager were showing, it seems that TMM/antenna were not passing corrected coordinates to iOS Location Services.

    Since, according to Trimble web site ( DA2 is capable of passing precise corrected coordinates iOS Location Services, it almost seems like we are missing some simple setting or a trick that enables this capability.


    Could you please pass all the information above to Trimble developers and ask them to clarify the following questions:

    1. Is DA2 capable of passing corrected coordinates to Location Services of  iOS 15.2 using a Web App?
    2. Is there an instruction for configuring it properly?
    3. What exactly did we do wrong during our testing that prevented us from receiving precise coordinates? Did we miss some hidden setting or a trick?


    The Trimble help portal article ( recommends disabling GNSS output transformation (using the Transformation Off setting) in scenarios like the one we were testing. I don't think we did it. Should this fix the problem?

    Joaquin San Juan

  • 2.  RE: Using Catalyst with a web App on iOS platform

    Posted 02-08-2022 12:33
    Hi Joaquin,

    Thank you for the detailed message. The behaviour you are seeing is not a limitation of DA2, but is a limitation of iOS itself, which will not report accuracies as provided by the connected receiver, and is normally limited to ~5m. There is no way around this, so any app that requires knowledge of the actual position accuracy will need to utilise an API to get the position directly from the receiver or from TMM. We expose a Web socket on TMM and this would be the recommended path forward if your app can support it. Note that the position provided to iOS location services by the DA2 is accurate (see notes below), it's simply that iOS does not report that accuracy.
    Some notes also:
    • On iOS the position in location services comes directly from the receiver. If you have TMM connected it will be a corrected position.
    • Because the position comes direct from the receiver location services will not benefit from transformations or geoids (orthometric height) applied by TMM.
    I hope this is clear. Please do reach out to me directly if you'd like to discuss more.

    Best regards,


    Mark Kellaway

  • 3.  RE: Using Catalyst with a web App on iOS platform

    Posted 02-09-2022 08:37

    Hi Mark, I read through this and I'm a bit confused by the response. .  

    It seems from  Joaquin's testing that the position was not being updated at all on iOS from the DA2.  See #5. From that remark it sounds like location services was not receiving an updated position from the DA2. 

    I'd be curious to hear the results if they shot over some control points.  This would be a true baseline for better understanding what is happening. 

    Jacob Wittenberg

  • 4.  RE: Using Catalyst with a web App on iOS platform

    Posted 02-09-2022 14:30
    Hi Jacob,

    That is an interesting point. One of the challenges with iOS Core location is that it's not possible to specify which location source is used, effectively it's a 'fused' location. Therefore, simply walking the receiver away from the iPad may have an unpredictable result. The DA2 provides a regular position to the device over a dedicated Bluetooth channel, and given that we know Bluetooth is working as the TMM connection is live it seems unlikely this is failing. 

    I agree, shooting over a known control point would help to validate. Another, slightly more crude, method is to look at the location on the map while inside with the iPad not connected to the receiver, then, with the receiver outside (close enough to connect) connect and see the location move on the map. This image shows my location in Google Maps on my iPhone while not connected to my receiver (in this case an R1):

    This image shows the position after connecting to the R1 placed outside (I'm sat in the same spot in my office):


    Mark Kellaway

  • 5.  RE: Using Catalyst with a web App on iOS platform

    Posted 02-11-2022 11:24
    Hi Mark,

    I am the customer that Joaquin did the field test with.

    I've run the test that you proposed, with R1 that I have and the same iPad Pro that Joaquin and I used for DA2 testing this Monday. Unfortunately, I'm not seeing the same results that you do with your phone. The point on the Google Maps does not change its position then I connect to R1 located outside of the house, about 7 meters way from iPad's position inside.
    I recorded iPad's screen while I was doing this test- (about 2 minutes and 200+ MB), here is the link:

    I also ran another field test with the same iPad and R1 yesterday. While they were connected and TMM was showing 0.5 m accuracy, the coordinates that all other apps was showing (including Google Maps) were not from R1. I did the "walk away test".  I also recorded a set of positions (about 100 points), loaded them to ArcGIS Pro and all the point were at the spot were I was standing with the iPad, not around the position of R1.

    So far it looks like at least my iPad's Core Location does not want to consume coordinates from R1 or DA2. The iPad is brand new, purchase specially for GSP tests.

    Do you have any suggestions on how to make it all working together? Should I call Trimble support or create a trouble ticket or something?


    Kirill Galkin

  • 6.  RE: Using Catalyst with a web App on iOS platform

    Posted 02-13-2022 17:41
    Hi Kirill,

    Thanks for taking the time to do these tests, given that both receivers exhibit the same issue it would seem to point to a client device issue. I'll contact you directly to figure out next steps.

    For anyone watching this thread, I'll update with an outcome when we understand what is happening.

    Best regards,

    Mark Kellaway

  • 7.  RE: Using Catalyst with a web App on iOS platform

    Posted 02-16-2022 16:07
    Hi Mark,

    Thank you for your help! Let me share my recent findings with you and community.

    In short, I finally was able to get coordinates from my R1 receiver to my iPad's Core Location.
    After googling for a solution I ran into several articles mentioning different GPS/Location related issues (not exactly mine) after upgrading to iOS 15.2. So I decided to check for updates for my iPad. There was a new version available - iOS 15.3.1 so I went ahead and installed it. After the update, I ran the "walk away" test with my iPad and R1 and it was successful. So I guess it was an iOS version issue.

    Anyway, my iPad is now working with R1 exactly as described by Mark - it consumes and passes to apps coordinates, but not accuracy value.


    Kirill Galkin

  • 8.  RE: Using Catalyst with a web App on iOS platform

    Posted 02-16-2022 16:17
    Thanks Kirill, I'm glad you got everything working!

    Best regards,

    Mark Kellaway

  • 9.  RE: Using Catalyst with a web App on iOS platform

    Posted 10-20-2023 02:10