Polygon Area in Feature Report and in AGOL

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5
03-30-2021 05:30 PM
AnnaSafonova1
New Contributor II

Hi!

I am building a report and everything seems to work fine except for one particular thing: when calculating the area of polygons in the repeat, the results in my report are not even remotely close to what is displayed for the same polygons in the default AGOL report in the panel on the right under the Data tab.

Here is what i have in my report:

${#location_extra_repeat_vertex}Area: ${location_shape_vertex | getValue:"area":"acres":"geodesic"|round:2} acres

${location_shape_vertex | mapSettings:””:10000 |size:700:180}

${location_extra_desc_vertex}${/}

All polygons, measurements, and descriptions show up, but the measurement numbers are off. For example, i have two records/polygons for a survey. The area of the first one is 4.45 acres in AGOL, but 0.9 acres in my report; 2.15 acres in AGOL and .43 in mine for the 2nd one. I tried changing both AGOL's and the report's choice of units to sq km, hectares, sq ml, etc. -- every time the results in AGOL would be different than the results in the custom report (e.g. in hectares, AGOL gives 1.8 and .85 for the 1st and 2nd polygons, and my report - .36 and .18). What am I missing here? I thought that "getValue:"area":"acres"" part should take care of the conversion between the default units and acres...switching between "geodesic" and "planar" also had no effect on the discrepancy in numbers...I'll appreciate ANY insight on what is going on!!

Thank you!

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5 Replies
jcarlson
MVP Frequent Contributor

Usually it's geodesic/planar that's the culprit, so it's odd that changing that wouldn't alter the results. Can you test it at different latitudes and see if the size of the discrepancy changes?

- Josh Carlson
Kendall County GIS
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AnnaSafonova1
New Contributor II
I've just submitted a new survey with two polygons and these are the areas
in acres for each one:
P1: Connect - 12.2, AGOL - 61.25, custom report - 12.26
P2: Connect - 46.9, AGOL - 234.85, c.report - 46.98

looks like it's AGOL's numbers that are inconsistent.
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jcarlson
MVP Frequent Contributor

Those AGOL numbers you're giving, where are those coming from?

- Josh Carlson
Kendall County GIS
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AnnaSafonova1
New Contributor II

Survey123 website, survey's Data tab

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jcarlson
MVP Frequent Contributor

Ah, that would be the layer's attribute table then. If you didn't otherwise specify when you created the layer, the layer's projection will be WGS84, which will not store accurate area figures. Safe to say you can disregard the AGOL numbers.

The area mismatch you're seeing is common enough that Esri has a FAQ page for it.

- Josh Carlson
Kendall County GIS
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