# Boundary Encroachment in Nice: Cadastral Map vs. Satellite Photo > # Boundary Encroachment in Nice: Cadastral Map vs. Satellite Photo - What Should You Do? **PROPERTY - BOUNDARY SURVEY** You opened Géoportail, overlaid the cadastral map on the s - URL : https://cassini-expertise.fr/en/boundary-encroachment-nice-cadastral-map-vs-satellite-photo/ - Langue : en-US - Mis à jour : 2026-11-02 - Site : Cassini Expertise (https://cassini-expertise.fr/) {“@context”: “https://schema.org”, “@type”: “FAQPage”, “mainEntity”: [{“@type”: “Question”, “name”: “Does the expert come to my property, or do I need to travel?”, “acceptedAnswer”: {“@type”: “Answer”, “text”: “The expert visits your property on site. The visit takes 2 to 3 hours depending on the size of the area. The expert who inspects the property is the one who signs the report.”}}, {“@type”: “Question”, “name”: “Is the expert assessment quote really free?”, “acceptedAnswer”: {“@type”: “Answer”, “text”: “Yes. The quote is free, detailed, and comes with no obligation. You know exactly what you’re paying for before you decide. No work or materials will be sold to you afterwards – the expert is independent.”}}, {“@type”: “Question”, “name”: “What happens if I do nothing?”, “acceptedAnswer”: {“@type”: “Answer”, “text”: “It depends on the issue: a crack that keeps growing can compromise the structure. Water infiltration can rot the roof framing. A waterproofing defect can degrade insulation. The longer you wait, the more expensive the repairs become.”}}, {“@type”: “Question”, “name”: “Does the expert work with my lawyer?”, “acceptedAnswer”: {“@type”: “Answer”, “text”: “Yes. The expert report is drafted to be used in an amicable settlement or in court proceedings. It is enforceable against an insurer, a property management company, a contractor, or before a court.”}}]} PROPERTY – BOUNDARY SURVEY You opened Géoportail, overlaid the cadastral map on the satellite photo, and spotted that small gap. Ever since, you’ve been convinced: your neighbour built their fence 30 cm onto your land. But an on-screen overlay is no substitute for a proper topographic survey. On the Côte d’Azur, actual boundaries often shift by 50 cm to 1 m compared to the cadastral record, due to land remodelling and historical inaccuracies. It’s not uncommon to see a case in [Nice](https://cassini-expertise.fr/nice-secheresse-argile-fissures-donnees-officielles/) where the owner was certain of a 40 cm encroachment… the boundary survey showed they were in fact on their own land, 20 cm short of the line. **See a real case.** [Retaining wall encroaching on the neighbour’s plot – Grasse](https://cassini-expertise.fr/en/natural-terrace-retained-wall-encroachment-neighbor-grasse/) : what the survey showed. ## What you see – and what it’s actually hiding ![boundary encroachment cadastral map satellite photo nice - Cassini Expertise](https://cassini-expertise.fr/wp-content/uploads/2026/09/avant-achat-maison.webp) *Cassini Expertise – independent building expert* You line up the cadastral map with the satellite photo, measure it on screen with a ruler, and it looks obvious. But the cadastral map isn’t a surveying document: its accuracy is on the order of a metre in rural areas, sometimes 50 cm in town. The satellite photo has a resolution of 30 cm to 1 m, and the overlay accuracy depends on orthorectification. In short, you’re stacking two sources of imprecision. What no one tells you: the cadastre is a tax document, not a legal one. The only evidence that holds up is a contradictory boundary survey (bornage). In Nice, with sloped land and retaining walls, the error can reach 1 metre. On complex terrain, as is common on the Côte d’Azur with its hillsides and retaining walls, discrepancies can reach 1 metre. Without a professional topographic survey using a total station or GNSS, you remain uncertain about the actual boundaries. ## The numbers that change everything: overlay uncertainty To know whether the gap is significant, you need to estimate the total error. The root mean square error (RMSE) combines the uncertainties: RMSE = √(σ_cad² + σ_photo²). In an urban area of Nice, the cadastral uncertainty σ_cad ≈ 0.5 m. A standard orthorectified satellite photo has σ_photo ≈ 0.3 m. That gives RMSE = √(0.5² + 0.3²) = √(0.25 + 0.09) = √0.34 ≈ 0.58 m. In practical terms, a 58 cm gap falls within the margin of error! Your 30 cm gap is therefore not statistically significant. What this means in practice: as long as the gap is below 2× RMSE (i.e. 1.16 m), you cannot conclude there is an encroachment. A contradictory boundary survey with a licensed surveyor (géomètre-expert) brings the uncertainty down to ±2 cm. That’s the only way to settle the matter. Article 646 of the French Civil Code requires a boundary survey in the event of a dispute, and only a licensed surveyor (géomètre-expert) may carry it out (art. L. 812-1 of the Commercial Code). ## What happens if you do nothing You leave things as they are. In 6 months, nothing will have changed. But in 2 years, if you sell, the buyer will require a boundary survey and will uncover the gap. You’ll then have to negotiate an easement or move the fence at your own expense. In Nice, an amicable boundary survey costs €1,500 to €2,500. In a contested case, expect €5,000 to €10,000 including lawyer and court-appointed expert fees. Worse: if the encroachment is real and the neighbour builds a wall or a pool, thirty-year acquisitive prescription may come into play. In 30 years, you could permanently lose that strip of land. It’s not uncommon to see a case in western Nice where the owner waited 15 years: the fence had become the legal boundary through prescription. ## Remedies and guarantees: what you can demand You can demand a boundary survey under Article 646 of the Civil Code: « Any property owner may compel their neighbour to have their adjoining properties surveyed and marked. » The procedure: send a registered letter with acknowledgment of [receipt](https://cassini-expertise.fr/expertise-vefa-06-83/) to your neighbor, proposing an amicable boundary survey carried out by a licensed surveyor. If they refuse, take the matter to the Nice judicial court. The licensed surveyor draws up a boundary report (procès-verbal de bornage), which stands as valid proof unless disproved. Act quickly: the longer you wait, the more complicated the situation becomes. ## Go further - [Cadastral marker moved on your property in Grasse? Proof by GNSS survey and remedies](https://cassini-expertise.fr/borne-cadastrale-deplacee-preuve-leve-gnss-recours-grasse/) 📅 **Updated on 18/08/2026** – By **Cassini Expertise**, independent building expert serving Alpes-Maritimes (06) & Var (83). Free quote: [04 22 46 06 04](tel:+33422460604). **Go further:** - [Boundary survey before buying property – Why it’s essential](https://cassini-expertise.fr/delimitation-propriete-avant-achat-immobilier/) - [Amicable boundary survey impossible in Nice: what to do when the neighbour refuses](https://cassini-expertise.fr/bornage-amiable-impossible-nice-procedure-judiciaire/) ## Frequently Asked Questions ### How do I know if my neighbour is encroaching on my property? Compare the cadastral map with your property’s actual boundaries. If structures or fences extend beyond the indicated limits, there is likely an encroachment. You can also call in a licensed surveyor for a precise boundary survey. ### What should I do once an encroachment is confirmed? Start by talking with your neighbour to reach an amicable agreement. If that fails, send a formal notice. As a last resort, take legal action to have the encroachment stopped and to claim damages. ### What’s the difference between the cadastral map and a satellite photo? The cadastral map is an official document showing the legal boundaries of parcels, but it can be imprecise. A satellite photo shows the actual state of the land, but has no legal value. For legal proof, only a boundary survey carried out by a licensed surveyor stands as valid. **See also:** [Cadastral Map vs Satellite Photo Overlay: Real Encroachment or Error in Nice?](https://cassini-expertise.fr/en/cadastral-map-satellite-overlay-encroachment-nice/) · [Boundary Encroachment on Neighbouring Land – Legal Remedies and Procedure](https://cassini-expertise.fr/en/boundary-encroachment-legal-recourse/) · [Boundary Encroachment: How to Identify It and Make It Stop](https://cassini-expertise.fr/en/boundary-encroachment-construction/) --- Source : https://cassini-expertise.fr/en/boundary-encroachment-nice-cadastral-map-vs-satellite-photo/