Creating a point symbol of a specific real-world size

Question

Hello,

I am wondering if it is possible, in ArcGIS Online, to create symbology for a feature layer of point data that shows/renders the points as a specific real-world size.

The points will represent human locations in the field, and each location must be 300 yards from any other location. Is there any way to create a point symbol that  shows/renders a radius of 300 yards? I know that the geofences can alert someone when they get close to another feature, but I need my users to be able to see this represented as they look at a map with the point data on it.

Is it possible to use Arcade to create a symbol of a specific real diameter/radius?

Or really any way at all?

Thanks in advance.

JustinJohnston · Answer

I think this can be done, but only for a specific scale of map and then you need to adjust some calculations for different scales.  For instance, if you have a map at 1"=100' scale and want real world diameters for points, you can create the points with a calculation to convert pt size to real world diameter at 100' scale.  If you have variable diameters, you can add an attribute field for diameter and reference the field in your calculation.  Start by adding the attribute field for "diameter" to your feature class.  Then in Symbology, "Allow Symbol Property Connections" so you get the little database symbols next to your symbology properties.

Click the database symbol for point size.

Click the little green "X" to enter an expression.

This is where the calculation comes in.  A point is 1/72 of an inch.  So you need to do the math for your map scale.  Assume you have 1"=10' scale (1:120) and are using a USFt horizontal coordinate system like state plane.  So the calculation is:  point = "diameter" field / 10 * 72.  Enter that and click ok, ok.

The result will have the correct real world diameter, but ONLY at the 1"=10' scale.  If you want a different scale map, you need to adjust your calculation.  For instance, for 1"=100' (1:1200) scale, the calculation would be point = "diameter" field / 100 * 72.  For 1"=50' (1:600), it would be point = "diameter" field / 50 * 72.  Etc. etc. so you need to adjust your expression to match you map scale.

ScottDBjelland · Answer

Hello Josh,

That is unfortunate but I appreciate your reply and insight.

Best,

Scott

jcarlson · Answer

Unfortunately, no. With Portal, you can do this using a Hosted Map Image layer, but to get this to work in AGOL would require an additional layer showing buffer polygons, which would need to be updated separately from the points layer. Still doable, but not as simple as you might want.

Arcade does have access to the $view_scale global in the symbology expression builder, but you'll find that even after a lot of fiddling, it still won't give you reliable results if you want real-world units.