Measuring intersecting polygons on 2 different layers


#1

I am looking for a way to measure an area that sits with in two polygons on two different layers… i.e.

Polygon of Field A on Layer 1 overlaps with Polygon of Field B on Layer 2 and I would like to know the area of the overlap of the two fields.

Apologies if this is a simple question but I have spent quite a bit of time on it and cant figure it out…

Thanks

Simon
North York moors National Park Authority


#2

Hi Simon,

I don’t think there is a way in Earthlight, though happy to be proved wrong! You could do it in the database - here’s what I’d use in Oracle:

select a.indexno, SDO_GEOM.SDO_AREA(SDO_GEOM.SDO_INTERSECTION(A.GEOLOC, B.GEOLOC, 0.005), 0.005, ‘unit=SQ_KM’) “overlap area” from tableA a,
tableB b where SDO_RELATE(A.GEOLOC, B.GEOLOC, ‘mask = ANYINTERACT’)= ‘TRUE’;

Again, it would be straightforward in MapInfo with an SQL Select:

Select tableA.indexno, cartesianarea(overlap(tableA.obj,tableB.obj), “sq km”) from tableA, tableB where tableA.Obj intersects tableB.Obj into Selection

Greg


#3

Hi Simon,

Thank you for your post. It is possible to measure area from two overlapping polygons in Earthlight.

The best tool to achieve this is the Clone tool. It is used for extracting intersecting part of the polygons.
Below you can find step by step guide on how to do this:


1 Please make sure that Inspect is set to ‘Active’ and then select a layer which stores a first polygon on the key pane. 2 Click on the **Clone** tool in the Edit tab. 3 Select the first polygon and click on the ‘**Clone record’ button**' on the right hand pane. 4 Select a layer which stores a second polygon. 5 Repeat step 3 for the second polygon - select the second polygon and click on the ‘**Clone record**’ button. 6 Click on the **Slice** tool. 7 Select **Mark & Move** tool and select those parts of polygons that you do not want to measure. 8 Click **Delete** button. Now you should see area of intersecting part on the right hand pane. 9 After finishing your measurements click on **Cancel** button to end the operation. Please be careful and do not click Save button, because it will save new record. Adam