topic Re: Help with Intersect / Intersection Attribute Rule in ArcGIS Pro Questions

Help with Intersect / Intersection Attribute Rule

Robswann — Thu, 30 Sep 2021 16:25:35 GMT

Hello, I am trying to determine the correct rule code for determining the amount of acreage within another polygon.

For Example: I have a feature named Tracts that may or may not contain floodplain acreage (Feature name Floodplain).

Could someone help me out? ..... This is what I have now.... but it is not pulling the correct acreage, and I think the correct function would be INTERSECTION, but not sure.

Thanks again

VAR FLOODPLAIN = FeatureSetByName($datastore, "RES_FLOOD_HAZARD")

VAR INTERSECTSFLOOD = INTERSECTS($FEATURE,FLOODPLAIN)

area(intersectsflood, 'acres')

Re: Help with Intersect / Intersection Attribute Rule

jcarlson — Thu, 30 Sep 2021 16:56:03 GMT

You guess correctly, you'll need Intersection to get the geometry of the overlapping area. However, this function requires two geometries as parameters, and you're working with a FeatureSet.

Simple Version: Getting Intersection of Single Feature

var floodplain = FeatureSetByName($datastore, "RES_FLOOD_HAZARD") // Grab the first item for the intersects featureset var flood_feat = First(Intersects($FEATURE, floodplain)) // Get intersection, calculate area var xs = Intersection(flood_feat, $feature) // Calculate acreage return Area(xs) // multiply by some value, depending on the area units in use

However, a single tract may intersect with multiple flood zones, and we may want to capture this information.

Complex: Return a List of Intersected Areas

var floodplain = FeatureSetByName($datastore, "RES_FLOOD_HAZARD") // Get FeatureSet of intersecting flood zones var flood_fs = Intersects($FEATURE, floodplain)) // Instantiate output string var out_str = 'Flood Zone Acreage:' // Iterate over FeatureSet for(var f in flood_fs){ // Get intersection, calculate area var xs = Intersection(f, $feature) // Calculate acreage var a = Area(xs) // multiply by some value, depending on the area units in use // Append to output string out_str += `\n${f.flood_zone_identifier_field} | ${a} ac` } return out_str

This will return something like

Flood Zone Acreage:
Zone AE | 12.1 ac
Zone X | 6.23 ac

Re: Help with Intersect / Intersection Attribute Rule

Robswann — Thu, 30 Sep 2021 17:53:34 GMT

Thanks again for the help. For some reason the expression states it is valid, but will not save? I have tried everything from saving closing out, restarting ?

Re: Help with Intersect / Intersection Attribute Rule

Robswann — Thu, 30 Sep 2021 18:42:40 GMT

Thanks I figured it out, any way I could just sum all the zones within that feature?

Re: Help with Intersect / Intersection Attribute Rule

Robswann — Mon, 04 Oct 2021 18:43:41 GMT

Thanks @jcarlson. Any way I could just sum all the zones within that feature to return a value of the total flood acreage?

Re: Help with Intersect / Intersection Attribute Rule

jcarlson — Mon, 04 Oct 2021 19:02:39 GMT

Oh, sure! Instead of an output string, you could just use a numeric value. Make these changes to the "complex" expression and see how it works.

Line  7 → var out_area = 0
...
Line 18 → out_area += a
...
Line 21 → return out_area

So instead of creating a cumulative string, you're adding up cumulative sum.

Re: Help with Intersect / Intersection Attribute Rule

Robswann — Mon, 04 Oct 2021 19:33:07 GMT

This is very helpful. Thanks again!