1Agreement to these terms
These Terms of Use (“Terms”) are a legal agreement between you and Zydeno, the developer of Trigmere (“we”, “us”). They apply to the Trigmere app for Android, its updates and everything it shows or produces (together, “the app”). By installing, opening or using the app you accept these Terms. If you do not accept them, do not use the app and uninstall it.
The Privacy Policy explains how the app handles data and forms part of these Terms. If we offer optional features under additional terms in the future, for example paid features, those terms will be shown to you before you accept them and will apply together with these Terms.
You must be old enough to enter into a binding contract where you live, or use the app with the consent and supervision of a parent or guardian who accepts these Terms for you. If you use the app for an organisation, you confirm that you may accept these Terms on its behalf; the consumer-protection provisions of these Terms apply only to consumers.
2Who provides Trigmere
Trigmere is developed and published by Zydeno (“we”, “us”), an independent developer. Contact: support@zydeno.com, website zydeno.com.
The app is a technical tool intended for adults. If you are under the age of majority where you live, use it only with the involvement of a parent or guardian.
3What Trigmere is and is not
Trigmere is a field book and calculation aid for surveying. It reduces levelling, adjusts traverses, runs COGO and coordinate conversions, and prepares computation reports from the observations and parameters you enter. It works offline, has no ads and needs no account.
Trigmere does not perform, certify or register surveys. It does not determine legal boundaries or property lines, does not contain the accuracy standards or tolerances of any country or state (you enter your own tolerance), does not connect to survey instruments, and does not include a geoid model or official transformation parameters. A computation report is a record of calculations, not a survey plan, certificate or legal document.
4Not a survey; check before you rely on it
Calculation aid only
Trigmere is a calculation aid. Results depend on your observations, settings and parameters. Have them checked by a qualified, licensed surveyor before relying on them for boundaries, set-out, construction or any legal or contractual purpose. Trigmere does not perform, certify or register surveys.
- Phone GPS is typically accurate to several metres and is not survey-grade. Use it only as an approximate location note, never as survey control.
- Coordinate conversions use published formulas and the parameters you choose. A wrong ellipsoid, zone, scale factor, height basis, geoid separation or transformation gives wrong coordinates that may still look plausible.
- Adjustments distribute misclosures by the method you choose. A result within your tolerance is not proof that the observations are free of blunders.
- In many countries boundary and cadastral surveys may only be carried out by licensed professionals. Using the app does not make you one and does not replace one.
5Your responsibility
You are responsible for:
- the observations you book, the condition and calibration of your instruments, and entering values correctly in the units you selected;
- choosing control, coordinate references, transformation and height parameters and tolerances that suit the job, and recording their sources;
- checking results independently before relying on them, and having them checked by a qualified, licensed surveyor where the work requires it;
- complying with the laws, licensing rules and professional standards for surveying where you work, and with site safety rules;
- any reports, files or set-out you provide to clients, employers or authorities, and the consequences of using them.
6Methods and file formats
Coordinate conversions use the authors’ own implementation of published formulas (Krüger series as given by Karney, 2011). Ellipsoid constants come from NGA and IAG publications. The app contains no code, tables or examples copied from surveying software or textbooks.
Trigmere exports DXF drawings and reads and writes CSV point files. DXF is a trademark of Autodesk, Inc. Trigmere is not affiliated with Autodesk. File formats are named only to identify file types; check imported and exported data in your other software before relying on it.
7Not professional advice; no safety-critical use
Check results before you rely on them
The levelling reductions, traverse adjustments, COGO results, coordinate conversions and reports that Trigmere shows are produced from models, published methods and data and the values you enter, and they can be wrong. Before relying on them for boundaries, set-out, construction, engineering design or any legal, cadastral or contractual purpose, have them checked by a qualified, licensed surveyor.
The app is a tool to help you plan and calculate. It does not give professional, engineering, legal or other expert advice, and using it does not create a professional relationship with us. You remain responsible for your inputs, for how you interpret the results and for what you decide to do.
Do not use the app as the only basis for a decision where an error could cause death, personal injury, damage to property or the environment, or legal or financial loss, and do not use it in a safety-critical system, in an emergency or to control equipment. Phone GPS positions are never survey control.
8Licence to use the app
Subject to these Terms, we grant you a limited, personal, revocable, non-exclusive, non-transferable and non-sublicensable licence to download, install and use the app on Android devices you own or control, for your own purposes (including your own projects and work for others). The app is licensed to you, not sold.
Except where these Terms, an open-source licence or mandatory law allow it (for example decompiling for interoperability where the law permits), you may not: copy, modify, translate or create derivative works of the app; decompile, disassemble or reverse-engineer it; rent, lend, sell, sublicense, distribute or publish it, or make it available for use by others over a network; remove or change any copyright, trademark or legal notice; or get around any technical limit of the app, including any future purchase, licence or advertising mechanism.
Open-source components and fonts in the app are licensed under their own licences, listed in the app under About → Open-source licenses. Those licences prevail for those components, and nothing in these Terms limits the rights they give you.
9Your data and backups
Your jobs, field books and settings are stored only on your device. You own them. We do not have a copy and cannot recover them if you lose your phone, uninstall the app, clear its storage or use “Delete all data”. Use “Export data” in Settings to keep your own copy. See the Privacy Policy for details.
The reports and files you create from your own observations are yours to use. We claim no rights in them.
10Fonts and open-source components
Trigmere is built with open-source software and a font, shown in the app under About → Open-source licenses:
| Component | Licence |
|---|---|
| Noto Sans typeface, © The Noto Project Authors, used unmodified | SIL Open Font License 1.1 |
| AndroidX, Jetpack Compose, Kotlin and kotlinx libraries and their dependencies | Apache License 2.0 |
The font and libraries remain the property of their authors. Nothing in these Terms limits the rights those licences give you for those components.
11Acceptable use
You agree not to:
- use the app in breach of any law or of other people’s rights;
- remove or hide legal notices or the calculation disclaimer from reports, or present the app’s output as a certified survey, plan or official document;
- copy, modify, redistribute, sell or reverse-engineer the app, except as allowed by law or by an open-source licence.
You also agree not to:
- use the app, or data obtained through it, in a way that is unlawful, fraudulent or harmful, or that infringes anyone’s intellectual property, privacy or other rights;
- enter, store or pass on other people’s personal data with the app unless you are allowed to do so;
- interfere with or disrupt the app or any service it connects to, introduce malicious code, or try to gain unauthorised access to any system;
- use automated means to extract data from the app or from the services it uses beyond normal personal use;
- present the app or its output as official, certified or endorsed by any authority, manufacturer or data provider.
12Intellectual property
The app, its design, text, icon and the name Trigmere belong to the developer, except for the open-source components and the font above, which belong to their owners. Other names are used only to describe things and belong to their respective owners.
The names Zydeno and Trigmere and their logos are our marks. You may refer to them to describe the app accurately, but not use them in a way that suggests endorsement. Names of third parties appear only to identify data sources, file formats, standards or rules; they belong to their owners and do not imply endorsement. If you send us feedback or ideas, we may use them without any obligation to you. We claim no rights in your own projects, data or exported files.
13Price, payments, ads and future paid features
Current version. The current version of Trigmere is provided free of charge, without ads and without in-app purchases or subscriptions. This describes the current version only. It is not a promise that the app, or any feature of it, will remain free of charge or free of ads.
Possible changes. We may at any time introduce advertising; offer paid features, in-app purchases, subscriptions or a paid edition; change which features are free; and set or change prices. Features that are free today may require payment in a future version. We will describe such changes in the store listing and release notes, and in the Privacy Policy where they affect data.
Purchases. Any purchase will be made through Google Play and processed by Google under the Google Play Terms of Service and its payment policies. Prices are shown in Google Play before you buy, including taxes where applicable. Subscriptions renew automatically until you cancel them in Google Play; cancelling stops future renewals. Refunds follow Google Play’s refund policies and your mandatory consumer rights, such as the right of withdrawal in the EU and the UK. Where you ask for immediate access to digital content during a withdrawal period, you may lose that right to the extent the law allows, and you will be asked to confirm this before you buy. You are charged only if you choose to buy something.
Ads. If the app shows ads, they are supplied by third parties. We are not responsible for the content of ads or for the products and services advertised, and any dealings with advertisers are between you and them.
Price changes. We may change prices for future purchases at any time. For an active subscription, we will announce a price increase as Google Play and the law require, and you can cancel before it applies.
14Disclaimer of warranties
To the maximum extent permitted by law, the app and everything it produces are provided “as is” and “as available”, without warranties of any kind, express or implied, including warranties of accuracy, reliability, fitness for a particular purpose, merchantability and non-infringement. We do not warrant that the app is free of errors, that calculated coordinates, levels or areas are correct for your purpose, that exported files open correctly in your other software, or that the app will work on every device or Android version.
In particular, and to the maximum extent permitted by law, we do not warrant that the app will meet your requirements, run without interruption, be compatible with your device or be free of errors or harmful components; that defects will be corrected; that data from third-party sources is accurate, complete or current; or that any feature, data source or price will remain available or unchanged.
Nothing in these Terms excludes or limits warranties, guarantees or conformity rights that cannot be excluded under the law that applies to you as a consumer (§16).
15Limitation of liability
To the maximum extent permitted by law, the developer is not liable for any indirect, incidental, special, consequential or punitive damages, or for errors in set-out or construction, boundary or contractual disputes, rework, delays, the cost of labour, equipment or materials, regulatory or professional consequences, loss of data, lost profits or business losses, arising from or related to the app, its output or decisions based on it, even if we were told such damage was possible.
Cap. To the maximum extent permitted by law, our total liability for all claims arising out of or relating to the app or these Terms is limited to the greater of (a) the total amount you paid us for the app and in-app purchases in the 12 months before the event giving rise to the claim and (b) 50 euros or the equivalent in your local currency. For the current version, which is free of charge, you have paid nothing.
These limits apply whatever the legal basis of the claim (contract, tort including negligence, strict liability or otherwise), even if a limited remedy fails of its essential purpose. They are part of the basis on which we make the app available.
What we do not limit. Nothing in these Terms excludes or limits liability for death or personal injury caused by our negligence; for fraud or fraudulent misrepresentation; for damage caused intentionally or by gross negligence; under mandatory product-liability law (including, where it applies, Directive (EU) 2024/2853 on liability for defective products and the UK Consumer Protection Act 1987); or any other liability that cannot be excluded or limited by law. Where the law allows only a partial limitation, our liability is limited to the extent it permits.
16Your rights as a consumer
If you use the app as a consumer, you benefit from the mandatory consumer-protection rules of the country where you live, and nothing in these Terms affects them. In particular:
- EU and EEA: your statutory rights, including those on the conformity of digital content and digital services under the national rules implementing Directive (EU) 2019/770 where they apply, and mandatory product-liability rules, remain unaffected.
- United Kingdom: your statutory rights, including under the Consumer Rights Act 2015, remain unaffected.
- Australia: our services come with guarantees that cannot be excluded under the Australian Consumer Law. Where the law allows us to limit our liability for failing to meet a consumer guarantee for services that are not of a kind ordinarily acquired for personal, domestic or household use, our liability is limited to supplying the services again or paying the cost of having them supplied again.
- New Zealand: if you acquire the app for business purposes, you agree that the Consumer Guarantees Act 1993 does not apply, to the extent the law permits.
- United States and Canada: some states and provinces do not allow the exclusion of implied warranties or the limitation of incidental or consequential damages, so some of the exclusions above may not apply to you. In Québec, the mandatory provisions of the Consumer Protection Act apply.
17Indemnity
To the extent permitted by law, you agree to indemnify and hold harmless the developer against claims, liabilities, damages, losses and reasonable costs, including reasonable legal fees, brought by third parties and arising out of (a) your surveys, set-out work and any reports or files you provide to others, (b) your breach of these Terms, (c) your violation of any law or of the rights of others, or (d) output of the app that you provide to another person, such as a client or employer. This does not apply to the extent a claim is caused by our own breach of these Terms or our negligence, or where local consumer law does not allow it.
18Changes, availability and termination
To the extent the law allows, we may change, update, add or remove features, change data sources, and suspend or discontinue the app, in whole or in part or in any country, at any time. We are not obliged to provide updates, maintenance or support, except where mandatory consumer law requires updates to keep the app in conformity.
You may stop using the app at any time by uninstalling it. Your licence ends automatically if you materially breach these Terms, and we may end or suspend it where the law requires. When it ends, you must stop using the app and uninstall it. Your data stays on your device under your control, so export what you need first.
Provisions that by their nature should continue after these Terms end continue to apply, including those on intellectual property, disclaimers, limitation of liability, indemnity, governing law and general provisions.
19Google Play
You obtain the app through Google Play. Your download, and any purchase you make, is also governed by the Google Play Terms of Service and Google’s policies. Where these Terms conflict with Google Play’s terms on the distribution, billing, refunds or licensing of apps obtained from Google Play, Google Play’s terms prevail to the extent of that conflict.
These Terms are between you and the developer only, not Google. Google is not responsible for the app or its content and has no obligation to provide maintenance or support for it. Android and Google Play are trademarks of Google LLC.
20Governing law and disputes
These Terms, and any dispute or claim arising out of or in connection with them or the app, including non-contractual disputes, are governed by the law of the country in which the developer is established, without regard to its conflict-of-laws rules. The United Nations Convention on Contracts for the International Sale of Goods does not apply.
The courts competent for the place where the developer is established have jurisdiction. If you are a consumer, you keep the protection of the mandatory provisions of the law of your country of residence, and you may bring proceedings in the courts of that country where that law allows it.
Before starting formal proceedings, please write to support@zydeno.com and give us at least 30 days to try to resolve the issue informally. This does not affect any time limit that applies to you by law or your right to use an alternative dispute-resolution body available to consumers in your country.
21General provisions
- Entire agreement. These Terms, the Privacy Policy and any additional terms you accept for optional features are the entire agreement between you and us about the app.
- Severability. If a provision is found invalid or unenforceable, it applies to the maximum extent permitted and the rest remains in effect.
- No waiver. Not enforcing a provision is not a waiver of the right to enforce it later.
- Assignment. You may not transfer your rights or obligations under these Terms. We may transfer ours, for example together with the app to another developer; where the law requires, this will not reduce your rights as a consumer.
- Events beyond our control. We are not responsible for failure or delay caused by events beyond our reasonable control, such as outages of networks, devices or third-party services, natural disasters or acts of authorities.
- Export and sanctions. You agree to use the app in compliance with applicable export-control and sanctions laws.
- No third-party rights. No one other than you and us may enforce these Terms.
- Notices. We may give notices in the app, in its store listing or release notes, or on this page. You can send notices to support@zydeno.com.
- Language. These Terms are written in English, which is the binding version. A translation, if offered, is for convenience only, unless the law of your country requires otherwise.
22Changes to these terms
We may update these Terms, for example when we change the app, introduce ads or paid features (§13), or when the law changes. The effective date and version at the top of this page show which version applies, and the version history (§23) summarises the changes.
For material changes we give reasonable notice before they take effect, for example in the release notes or in the app. If you keep using the app after the changes take effect, you accept the updated Terms; if you do not agree, stop using the app and uninstall it. Changes do not apply to disputes that arose before they took effect.
23Version history
| Version | Effective | Changes |
|---|---|---|
| 1.0 | 2026-10-18 | First published. |
24Contact
- Developer: Zydeno, the developer of Trigmere on Google Play
- E-mail: support@zydeno.com
- Website: zydeno.com
See also the Privacy Policy.