I'm relatively new to QGIS and I'm using it to run viewshed analysis to assess impact of newly constructed transmission lines on private properties. I generate two viewsheds, one at 500m from the transmission line and another from 500m to 1,500m. I then vectorize the the viewsheds and clip to the boundary of the property of interest. I've developed a model to automate the process. I can post up the model if it's relevant.
Each property has a land title cadastre and I want to know the overlap area of each viewshed over each land title. I'm using the overlap analysis tool to do this calculation and most it works ok but sometimes it won't "see" one or more of the overlapping layers. I can't see a reason for this.
I can calculate the area of the 1,500m zone using the field calculator.
Any suggestion on why this is happening?
The first images shows the Overlap Analysis attribute table missing the calculations for the 1,500m viewshed. The 500m calculations have worked and apportioned the impacted area over the two land titles.
The second image shows the Viewshed Analysis clipped to the boundaries of the subject property. The blue layer running diagonally through the property is the transmission line easement, with transmission line and towers within it. The purple is the 500m viewshed, the grey is the 1,500m viewshed and the red is unaffected land.
