How to calculate a power-line easement corridor: from the tower schedule to area per parcel
How much land a line affects is hidden in the coordinates of its towers.
Field takeaways
- The line axis is drawn from the coordinates in the tower schedule; if you doubt the list, do not start the calculation.
- The corridor width is the line project's decision, not the software's.
- For each parcel, the easement area is the intersection of the corridor with the parcel.
- Tower sites and the corridor are separate items; mixing them spoils the area table.
- The calculation prepares the plan; registration and valuation are the authority's job.
It starts with the tower schedule
The route of a power line is written in its tower schedule: the number, type and coordinates of every tower. The line joining consecutive towers is the axis of the line. All of the accuracy of the easement calculation rests on that list. If one tower was entered in the wrong coordinate system, or two towers are out of order, the corridor crosses the wrong parcels, and no amount of care later on will put the result right. The first job is to confirm the list's coordinate system and tower order.
The project sets the corridor width
The width of the strip left on either side of the axis is set in the line project, according to the voltage, conductor swing, tower type and the criteria of the operator the line belongs to. So do not guess the width or take it from a generic table online; use the value approved in the project. If the width changes from span to span, enter a separate value for each span. The corridor is the area offset from the axis by that half-width on both sides.
Intersection with the parcels: the real calculation
The easement area of each parcel is the intersection of the corridor with the parcel boundary. Cadastral parcels and the corridor must be in the same coordinate system; in Türkiye that is usually an ITRF96-based TM zone, and mixing it with old ED50 data shifts the corridor by metres across the parcel. Once the intersection area is found, it goes into the table next to the parcel's registered area. Where the line clips a parcel at one corner, very small areas appear; do not delete them, keep them on their own rows.
Tower sites are a separate item
Along the corridor the land usually stays with its owner, with an easement established over it. The ground a tower stands on is handled separately in most projects and acquired outright. Counting both in the same area inflates the table: compute the tower-site area apart from the corridor area and show them on two separate rows. How each item is acquired is the project's and the authority's decision.
In Türkiye: the plan and the declaration
In Türkiye, Expropriation Law No. 2942 allows an easement to be established instead of taking ownership when that is enough for the purpose. The computed areas are carried into the expropriation plan and the declarations; the plan shows the parcels, the corridor, the towers and the area table together. If you work in another country the geometry is the same, but the width criteria and the document format follow that country's rules.
What this calculation is not
This calculation is the technical basis of an expropriation file. Registration, valuation and official steps belong to the competent authority, and determining official boundaries and areas is licensed survey engineering work. The areas found here should not be used as an official basis until they have been through that check.
Run this calculation along the whole line.
MapLab Kamu builds the easement corridor from a power line's tower schedule (DTL) and prepares expropriation plans, declarations and measurement sketches, with Netcad NCZ and DXF output. Built for Türkiye's procedures and adaptable to other countries on request. Web and Windows, on request.
Frequently asked questions
Where do I find the corridor width?
In the line project and the criteria of the operator the line belongs to. A value taken from a generic table may not match the one approved for the project.
Which coordinate system is the tower schedule in?
It should be stated in the schedule itself. If it is not, check a few towers in the field or against a known base map; if the system is wrong, the whole corridor shifts.
What if the line only clips the corner of a parcel?
A small easement area results. Do not delete it; keep it on its own row in the table and let the authority decide.
Is the area I computed enough for registration?
No. It is a technical basis; registration and valuation go through the competent authority and licensed survey engineering.
Technical references
The field guidance in this article is aligned with the technical and official references below.
Related: Registry area comparison · Why parcel lines shift · ED50 to TUREF · MapLab Survey