Lisa,
The joys of coordinate systems and transformations. For most, persistence has payed off but this can take some time, a lot of time. There is a lot going on with a high accuracy GPS and Collector. First there is your GPS that is working on a given coordinate system and datum, you are then applying a local site correction to this data to zero in the accuracy and/or use a custom coordinate system, this data is then passed to Collector either directly or with an initial transformation within the GPS or its application, Collector then takes this information and applies additional transformation(s) to display the data and/or post it to AGOL or your own enterprise site, then you are accessing this data and again applying more transformations to get the data where it needs to be. Lots of room to loose track of everything that has been applied so understandable that it is confusing.
Here are some thoughts as I think through the issue you described. You do not really need to answer but you are welcome to.
1) I have not had the opportunity of working with a local site system using Collector. We do have a site system setup for our surveyor but for GIS we typically run off the State VRS system. However, the first thing I would confirm is that your local corrections are getting applied to your base coordinate system and this info is getting sent to Collector and not just the raw GPS data. Especially if these corrections are close the error you are observing. The error is rather large and I would guess your corrections are not that large unless you are also including a transformation at that point.
2) Was the correct base coordinate system selected for your GPS and was the local site configured correctly? Also look at units such as meters vs international feet vs US feet.
3) How does collector work with local site corrections? Is it exclusively handled in the Trimble software before passing the data to collector? What data is being passed to to Collector? Is the corrected data getting passed or the uncorrected?
4) What data is stored in the ESRI GNSS metadata (Latitude, Longitude, Altitude) when collecting a point? Is it the base coordinate system data or the local site corrected data? Have you tried restoring the points back from the metadata to see how they place in relation to your surveyors control data.
Other considerations
1) confirm the coordinate system your surveyor is using and that these points are correct once brought into the GIS system you are working with to view the data. Do you have imagery of high enough accuracy to confirm against?
2) confirm what coordinate system the data being stored in the ESRI GNSS metadata for Latitude, Longitude and Altitude. This is the raw coordinate data from the GPS less any transformations and will be height above ellipsoid for the altitude data, not elevation. I do not know if this will contain the corrections for your local site. You may want to check with Trimble on that item. I really need to get a loaner from Trimble this winter to learn more about their units.
3) try and use this raw data and applicable transformations to get your data into your system with minimal transformations being applied. The ProjectZ tool is great for this initial process. This typically eliminates anything that may have been applied by Collector, AGOL or when pulling your data back into a local system.
4) load in your surveyors control data and have your coordinate system set for the data frame first. Bring in your problematic GPS data and experiment with different transformations on your raw data. I prefer to do this using ArcGIS Desktop 10.x as you have more fixed control of the transformation being applied (may just be me and having used Desktop for decades). ArcGIS Pro can automatically apply transformations that are not necessarily the correct one to be using.
5) note how the different transformations shift your data. You may just find one that works. You may note one moves the data up and down, another moves the data left and right. You may need to perform one to move the data up and down then apply one that moves the data left and right. That is how we found we needed to use two transformations to go from NAD83 to NAD83(2011) for our State Plane System.
6) use logic, there are hundreds of transformations out there but most can be eliminated by simply looking at what system am I starting from and where do I need to go.
7) any chance your local site corrections or a transformation is getting applied twice?
If you can provide a sample of your data, surveyor control data and the coordinate system info I would be glad to take a look. That’s what weekends are for, right. Sorry, I do not have a specific solution but you can do this.
Have a great evening.
