Unsuccessful at getting Z-Value in Feet

[SheldonBina2]

Hello-

I am using Field Maps connected to a Leica GG04 GNSS Receiver.  I have created an expression using Geometry($feature).Z in my Web Map and also created an Elevation field and calculated geometry using the Point Z-Coordinate Property in ArcGIS Pro.  The value I get is the correct Mean Sea Level elevation, but it is in meters.  I am using the Geoid18 model and have the vertical coordinate system set as NAVD88 (height) (ftUS) in my feature layer, and have settings set to US Feet in the Leica Zeno Connect App.  I'm not sure if my workflow is complete or is this a limitation of collecting Z-Values in Field Maps?  Any guidance/assistance is appreciated.

Thank You!

[KevinBurke · Accepted solution]

Hi @SheldonBina2 

That is correct. In this case because the elevations are coming from Zeno Connect with a vertical coordinate system of NAVD88 in meters, once Field Maps supports vertical datum transformations, the app should be able to transform into NAVD88 in feet. However because Field Maps doesn't currently support vertical datum transformations, the elevations obtained from Zeno Connect remain as-is in units of meters.

This is why I suggested that since the elevation values themselves are accurate from Zeno Connect and all that's needed is a unit conversion, you could use the Project geoprocessing tool in ArcGIS Pro to vertically transform to NAVD88 in feet.

Or, if all that's needed is the actual elevation values themselves, you could use ArcGIS Pro to add the Z values from the features geometry into the attribute table and then simply use the Field Calculator to convert to feet. This of course doesn't update the values that are still part of the geometry still being in meters. 

With regards to horizontal transformations, yes, this happens in Field Maps per the Location Profile configured and the datums/projections chosen between the GNSS correction service and the web map's spatial reference. 

Thank you

-Kevin

[SharonUngerer_DNREC]

This post is super helpful thank you!  I just want to make sure I am on the right track because there is esri documentation out there that the location profile doesn't change the GNSS metadata fields collected from receivers. 

Is this true only of the metadata fields?  Does the location profile perform a datum transformation on the feature geometry and the metadata fields? 

"Latitude—Position received from the GPS receiver prior to applying data transformations in the location profile
Longitude—Position received from the GPS receiver prior to applying data transformations in the location profile
Altitude—Ellipsoidal height received from the GPS receiver (not orthometric height, as used for z-values)"

Collector: https://doc.arcgis.com/en/collector/android-phone/help/high-accuracy-prep.htm#ESRI_SECTION1_C992B4FE... 
Field Maps: https://doc.arcgis.com/en/field-maps/android/help/high-accuracy-data-collection.htm 
Collector (Classic): https://doc.arcgis.com/en/collector-classic/ios/create-maps/gps-map-prep.htm  

[ADS]

Hello,   I will ask the same question for us for year 2023.    When will US ft. be usable in any of these apps. We are trying to not post processs.   

[MikeDahm]

I have been waiting a long time for this feature.  We got several trimble units and use Field Maps (was collector) letting our clients know this feature was coming.  Second half of 2021 was a long time ago.

[RyanJalynski]

I'm also waiting for this feature to be available. Is this no longer being considered for development?

[KevinBurke]

Hi @ADS , @MikeDahm, and @RyanJalynski I apologize for the delayed response. Support for vertical datum transformations is absolutely still on our mid-term road map for Field Maps. More information will be provided as it becomes available for this work. 

If the goal is to just see the converted Z values in units of US Feet for point features in the form while out in the field, then this is possible through the use of the Calculated Expressions through the Field Maps Designer (ArcGIS Online, Enterprise 11+). In that case you would create a double field in the attribute table, and add the following calculated expression to the field in the smart form:

// Get the Z value

var geom = Geometry($feature)

if (IsEmpty(geom)) {

    return null

} else {

    return geom.Z * 3.28084

}

While that will store the Z value as an attribute in the new field in units of feet, it will not convert the actual Z value that is part of the point geometry. That will still be in units of meters. If that's the goal then, as I mentioned in an earlier post, you will need to use the Project geoprocessing tool in Pro to covert the vertical CS to one that supports US Feet. 

Please let me know if you have any questions.

[MikeDahm]

Is this converting elevation in height above MSL?  Or is this still height above ellipsoid?  We need height above mean sea level.

[JonRedd]

Thank you Kevin, this helps tremendously for point layers. Do you happen to have a current option for line features. In ArcPro you can utilize the calculate geometry attributes and I have it set in a model tool to get the minimum z value to populate one field for a pipe feature and the maximum z-coordinate to populate another field. I am switching to hosted feature layers to get rid of all post processing through ArcPro and only utilizing Online and Field maps for collecting the data. 

[KevinBurke]

Hi @JonRedd 

I was able to leverage the following calculated expression for the form in Field Maps to obtain the maximum Z value:

var geom = Geometry($feature);

var z = [];

for (var part in geom.paths) {

    var line_part = geom.paths[part]

    for (var i in line_part) {

      var vertex = line_part[i]

      var zval = vertex.z

      z[i] = zval

      }

    }

    return Max(z)

for the minimum Z, just update the last line from Max to Min.

In my scenario I published a line feature and added two double-type fields, one for max Z and one for min Z and added this as a calculated expression for both using Field Maps Designer. 

Let me know if you run into any issues with those.

Thank you!

[Aymen_Farhat]

Any updates?