Hi Matthew,
Unfortunately the first option isn't possible as Field Maps doesn't have a transformation between 4277 and the British National Grid coordinates used for OS mapping in the uk (code: 27700). The latter is a projected coordinate system using Eastings and Northings, so can't take in data in lat and long format without an appropriate transformation.
The second option uses the same pair of coordinate systems (GNSS to map) that I've been using previously, namely 4258 - 27700. Field Maps gives me a choice of 15 different transformations to achieve this, with OSTN15 mentioned in two of them. Up to now I've been using
ETRS_1989_To_OSGB_1936_OSTN15. I could experiment with the TMM output set to ETRF1989 and perhaps try some different transformations.
My best way to test the accuracy these settings achieve would be to go to a couple of my local OS 'passive stations'. These are geodetic quality ground marks installed by the Ordnance Survey in accessible locations. They are no longer maintained, but most still exist and I've visited 4 of them in the past. Unfortunately, as I have a Catalyst On Demand subscription, I'd have to spend an hour or two of my subscription to run some tests, which I'm a bit reluctant to do.
I do wonder if the transformation ESRI lists as '
ETRS_1989_To_OSGB_1936_OSTN15' is actually designed to take in the OSNetv2009 realisation of ETRS89 and output British National Grid coordinates, but the fact its name just references ETRS 1989 makes me unsure... I've had a reasonable dive into this document: https://www.ordnancesurvey.co.uk/documents/resources/guide-coordinate-systems-great-britain.pdf but I must admit to strugging to get my head around all of it!
Thanks again
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Richard Pearson
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Original Message:
Sent: 01-31-2023 17:08
From: Matthew Morris
Subject: DA2 Catalyst - Reference frames and interaction with ArcGIS Field Maps using British National Grid coordinates
So here you likely have 2 options for configuration - the difference being where the ETRS89 to OSGB36 transformation is done. I would expect the following two configurations to provide equivalent results:
- Transformation done in Trimble components:
TMM GNSS Output = OSNetv2009 (formerly labeled Ordnance Survey in TMM) either by Auto or selected from list
Field Maps uses a GNSS Profile with GNSS Coordinate system = GCS OSGB 1936 (ESRI:4277) and Map coordinate system = <based on web map>; could be no-transformation if web map is based on GCS OSGB 1936 - Transformation done in Field Maps:
TMM GNSS Output = ETRF1989 as selected from list
Field Maps uses a GNSS Profile with GNSS Coordinate system = GCS ETRS 1989 (ESRI:4258) and Map coordinate system = <based on web map>; will use Esri's implementation of the OSTN15 transformation if web map is based on GCS OSGB 1936
Let's see if @Tom Harrison can validate that for me.
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Matthew Morris
Original Message:
Sent: 01-31-2023 13:21
From: Richard Pearson
Subject: DA2 Catalyst - Reference frames and interaction with ArcGIS Field Maps using British National Grid coordinates
Hi @Matthew Morris
Thanks for your reply. I'm not sure how I would need to set up Field Maps to take advantage of the Trimble sdk?
As I've previously understood it, I needed to set the GNSS output in TMM and then set up an appropriate location profile in Field Maps to transform the TMM output into the map coordinate system?
I'm currently using a Field Maps location profile that uses the ETRS_1989_To_OSGB_1936_OSTN15 transformation, is that correct I wonder?
Many thanks
Richard
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Richard Pearson
Original Message:
Sent: 01-31-2023 12:03
From: Matthew Morris
Subject: DA2 Catalyst - Reference frames and interaction with ArcGIS Field Maps using British National Grid coordinates
Hi @Richard Pearson. In this case, the Trimble components (whether that be TMM or the Trimble SDK used in ArcGIS Field Maps) will be used to perform the transformation (and projection) from ETRS89 to OSGB36 National Grid using the official OSTN15 grid transformation. Let me know if that answers the question. Thanks.
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Matthew Morris
Original Message:
Sent: 01-31-2023 02:54
From: Richard Pearson
Subject: DA2 Catalyst - Reference frames and interaction with ArcGIS Field Maps using British National Grid coordinates
Many thanks Mark,
I've checked and the status view does indeed show that OSNetv2009 is used when the GNSS output is set to auto. I'll experiment with that setting and see how it matches up with what I've used before.
Just wondering if you have any thoughts on whether the EPSG 4258 to 27700 transformation is the most appropriate to use to get to British National Grid coordinates please?
Many thanks
Richard
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Richard Pearson
Original Message:
Sent: 01-30-2023 19:29
From: Mark Kellaway
Subject: DA2 Catalyst - Reference frames and interaction with ArcGIS Field Maps using British National Grid coordinates
Hi Richard,
If you open the 'Status' view in TMM you will be able to see the GNSS output reference frame being used. We would expect the default to be OSNetv2009.
Regards,
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Mark Kellaway
Original Message:
Sent: 01-30-2023 05:23
From: Richard Pearson
Subject: DA2 Catalyst - Reference frames and interaction with ArcGIS Field Maps using British National Grid coordinates
Hi there,
I wonder if anyone can tell me which reference frame TMM uses when GNSS output is set to 'auto' and the device is located in the UK please?
I'm trying to find the best match between the TMM GNSS output setting and the transformation used in Field Maps, so that I end up with accurate Ordnance Survey grid references within Field Maps.
I have been using ETRF2000 (EPOCH:2010.5) as the TMM output reference frame, but have now discovered that is specific to The Netherlands...
The transformation I've been using in Field Maps is ETRS_1989_To_OSGB_1936_OSTN15, which transforms from EPSG 4258 to 27700
Many thanks in advance
Richard
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Richard Pearson
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