Calculate area of polygon I draw

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06-20-2021 08:19 AM
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BetsyMacWhinney
New Contributor

Hi,

I'm a newish/beginning user, and I'm trying to calculate the area of a polygon I draw using map notes.  I understand that I can use the measurement tools to measure after I've drawn, but this is extra work and clunky, in that I have to somehow record the area  manually after I've measured.

I am trying to analyze landuse types within several 1K circles, and each may contain several different land uses that I outline with map notes.    I would love to be able to click on each of the polygons I draw and have it show the area and also be able to add that to the legend.  

Thanks for any tips!

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JayantaPoddar
MVP Esteemed Contributor

I would recommend creating an empty shapefile with desired schema (ArcGIS Desktop or QGIS), and uploading it to ArcGIS Online (if not publishing it from ArcGIS Desktop), thus creating a hosted feature layer. 

You can edit the hosted feature layer, creating polygons and adding desired attributes along with the calculation of area and length of polygons.

 



Think Location

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DavidPike
MVP Frequent Contributor

Depending on your privileges on ArcGIS Online, Go to you 'Content'  --> 'Create' (near the top left) --> 'Feature Layer' --> 'Build a Layer' --> 'Polygons' then use that as the hosted feature layer for editing.

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JayantaPoddar
MVP Esteemed Contributor

I would recommend creating an empty shapefile with desired schema (ArcGIS Desktop or QGIS), and uploading it to ArcGIS Online (if not publishing it from ArcGIS Desktop), thus creating a hosted feature layer. 

You can edit the hosted feature layer, creating polygons and adding desired attributes along with the calculation of area and length of polygons.

 



Think Location
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BetsyMacWhinney
New Contributor

Thank you! I don't have ArcGIS Desktop or QGIS but maybe I should look into QGIS.  Appreciate your help!

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DavidPike
MVP Frequent Contributor

Depending on your privileges on ArcGIS Online, Go to you 'Content'  --> 'Create' (near the top left) --> 'Feature Layer' --> 'Build a Layer' --> 'Polygons' then use that as the hosted feature layer for editing.

BetsyMacWhinney
New Contributor

Thanks! This gets me a lot closer.  I do have the necessary permissions to create a feature layer.  I'm a little unclear on how to calculate the area of the polygon I created in this fashion.  Thanks so much for your time.

 

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JayantaPoddar
MVP Esteemed Contributor

That's a really good method mentioned by David. In case you have chosen "Build a Layer" > Polygons from the templates, Shape_Area and Shape_Length fields are already available (These fields are automatically calculated). You just need to show those fields in attribute table.

JayantaPoddar_0-1624219465650.png

 

JayantaPoddar_1-1624219517137.png

 

You could also Show the Field from Item Details page of the Hosted Feature Layer (Data tab > Table).

JayantaPoddar_2-1624219691829.png

In case you see blank pop-up of Shape_Area while creating the shape, keep it blank and close. It will be calculated automatically.

JayantaPoddar_0-1624220620185.png

 



Think Location
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DavidPike
MVP Frequent Contributor

I should also say that these areas are almost useless as the shapefile is created in web mercator.  I'd recommend creating a new attribute expression where:

AreaGeodetic(geometry($feature), 'kilometers')