Cordinate systems and transformations with collector and high accuracy GNSS GPS - best practice

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05-22-2018 07:47 PM
LanceCole
MVP Regular Contributor

We have been testing a high accuracy GNSS GPS with Collector (Aurora and 18.0.1) in a development environment and utilizing ArcGIS online as our Portal.  As we plan to move to the production environment questions have arose pertaining to minimizing data translations to maintain accuracy.  The GPS utilizes and outputs in  the GCS NAD 1983 2011 coordinate system from our State VRS network.  We have been translating this to WGS 1984 Web Mercator Auxiliary Sphere for use with ArcGIS Online and its related basemaps.  Our production system also utilizes the GCS NAD 1983 2011 coordinate system, specifically the NAD 1983(2011) State Plane and no translations are needed between the GPS and production servers; however, we plan on continuing to utilize ArcGIS online as our Portal for collector.  What is the best or recommend approach to maintain the collected coordinate data accuracy?

We are considering:

1) generating our own basemaps on our local servers using the GCS NAD 1983 2011 coordinate system and pushing these up to ArcGIS online and sideloading them directly onto our Collector systems (when/if they will fit).  This would save on credits used for building the tiles but we will still be utilizing credits for storage.  Subsequently, we would publish our features utilizing the same coordinate system. This is currently our preferred approach as there would not be any translations required.

2) continue with the current approach of collecting GPS data using GCS NAD 1983 2011, translating to WGS 1984 Web Mercator Auxiliary Sphere on ArcGIS Online and then translating back to the NAD 1983(2011) State Plane we utilize internally.  We have noted a definite shift in the data collected utilizing this method when compared to data collected by our surveyor utilizing a total station or survey grade GPS on our own local network.  I have experimented with different translations but the WGS_1984_(ITRF08) to NAD_1983_2011 we are utilizing provides the best match.  

3) a question for the ESRI team is it possible to utilize the ArcGIS online basemaps without Collector automatically using the WGS 1984 Web Mercator.  We did try and publish a feature using the GCS NAD 1983 2011 coordinate system but the Maps/Collector automatically adopts the basemap coordinate system.  We were also not positive on how the point data was being handled with a mixed coordinate system and most likely introducing further translations and potential errors.  

It is ironic that a few years ago GIS data that was accurate to a couple of meters we considered fantastic and now we are looking at a target accuracy of 10cm and achieving an actual accuracy of less then 2cm

1 Solution

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LanceCole
MVP Regular Contributor

Follow-up

1) we did end up creating our own base maps and side loaded them onto our collector devices.  Not only did this save on credit usage for our ArcGIS online storage but the side loaded maps are substantially faster especially in areas with poor cellular connectivity.

2 & 3) collecor still does not fullly support x,y,z transformations so we have remained with the native coordinate system for collector.  This is being worked on by ESRI and hopefully will be available in the near future.  We also were apple to confirm the latitude, longitude and altitude attribute values stored when using a GNSS GPS are in the raw data coordinate system for the GPS utilized.  Do note the altitude values are currently height above ellipseoid and need to be transform to actual elevation.

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30 Replies
LanceCole
MVP Regular Contributor

Follow-up

1) we did end up creating our own base maps and side loaded them onto our collector devices.  Not only did this save on credit usage for our ArcGIS online storage but the side loaded maps are substantially faster especially in areas with poor cellular connectivity.

2 & 3) collecor still does not fullly support x,y,z transformations so we have remained with the native coordinate system for collector.  This is being worked on by ESRI and hopefully will be available in the near future.  We also were apple to confirm the latitude, longitude and altitude attribute values stored when using a GNSS GPS are in the raw data coordinate system for the GPS utilized.  Do note the altitude values are currently height above ellipseoid and need to be transform to actual elevation.

DonRodgers
New Contributor III

Lance, we are looking for a way to collect z coordinate data with our Trimble R2 and the ArcGIS Collector app. Can you tell me how you make the HAE to actual elevation transformation?

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LanceCole
MVP Regular Contributor

I would be glad to help.  A few quick questions.  

1) do you have access to ArcGIS Pro?  It is not needed but the approach is different between ArcGIS and ArcGIS Pro.

2) what corrodinate system is your Trimble R2 configured?

3) what corrodinate systems do you want your final data to be in?

DonRodgers
New Contributor III

Lance: I have been using ArcGIS Pro to make and share the web maps on AGO.

I don't completely understand your question #2. In my profile on my Collector app my GNSS Coordinate System is set to GCS NAD 1983 2011. Is that what you are asking?

I want to end up with horizontal data in NAD 83 and vertical data in NAVD 88.

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LanceCole
MVP Regular Contributor

Excellent, I will write up a quick "How-To" this evening using your information. I do have a few more questions

When you say NAD 83, I assume GCS_North_America_1983, WKID: 4269?

On the vertical data do you want the NAVD 88 to be in Feet, US FT or Meters?

I am also assuming you have configured your database and are receiving the GPS metadata with each point when collected to AGOL, correct?

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BillFox
MVP Frequent Contributor
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DonRodgers
New Contributor III

Lance, thank you for your quick and thorough response. I can clearly see that your knowledge base and experience far exceeds mine, but I will try to keep up.

In response to your follow-up questions:

When I say NAD 83 I mean that the Seiler Rep who walked me through the Trimble R2/ArcGIS Collector setup had me enter NAD 83 2011 as the GNSS Coordinate system and as the "to" system in my Datum Transformation box in my Profile. All the data that our organization stores on our in-house databases is NAD_1983_StatePlane_Indiana_East_FIPS_1301_Feet.

On the vertical data I ultimately want my data to be in US Feet.

With respect to metadata fields what I have done is to add metadata fields to a published Feature Service Layer and then added that new Feature Service layer to my Web Map. I have attempted to Configure a feature service to store GPS metadata. The obstacle that I encountered is that the instructions indicate that I should add field names to my feature attribute table and these field names are longer than that field will accept.

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LanceCole
MVP Regular Contributor

I will reply to your new question posted at Is it Possible to Collect Accurate Z Coordinate Values with Collector and Trimble R2.  I will also be deleting my response below and moving it to your question.

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