Tools
Governing: Decreto 25/2018 art. 3 and Annex 3; RD 191/2026 art. 3.5; CAIB "Cuidamos la Posidonia" cartography page. Builds on: L2.2.
The official sources
The Govern's Posidonia site lists the tools it recognises. Keep this list on the chart table:
| Tool | What it is |
|---|---|
| ideib.caib.es/posidonia/ | The official web app "Ajuda per fondejar a les Illes Balears": meadow cartography and buoy-field boundaries |
| Projecte Posidonia | App (Android and iOS) listed by CAIB |
| Posidonia Maps | App listed by CAIB |
| Donia | App listed by CAIB |
| IDEIB viewer (ideib.caib.es/visor) | Add the layer by searching "posidonia" in the layer list |
| Ecocartográfico de Baleares | KML files published by the ministry for Ibiza, Formentera and Menorca |
| LIFE Posidonia cartography | PDF and KMZ files from the 2001–2005 LIFE project |
| IEO Atlas de las praderas marinas de España | National atlas |
The CAIB buoy-field page adds that the latest meadow mapping and the field boundaries are in the web app.
Which map wins?
Decreto 25/2018 art. 3.1 requires the Govern to approve official cartography by order published in the BOIB. Until then, transitional provision 3 says the reference is Annex 3 (the ministry ecocartography, the LIFE Posidonia maps and the old CAIB anchoring viewer), and that where the sources disagree, the one showing the larger meadow area applies. That is worth remembering: "my app showed sand" is not a defence if another official source shows meadow.
RD 191/2026 art. 3.3 gives the ministry five years from April 2026 to revise the national cartography, including dead meadow, and to update it at least every six years after that. Art. 3.5 obliges authorities to publish where the buoy fields are and how they are managed.
Using the maps properly
- Plan before you arrive. Pick two or three sand patches and a buoy field as a fall-back while still at sea.
- Check the scale. Mapping polygons are not survey-grade. Small sand pockets inside a meadow may not show, and meadow edges move.
- Allow for your own position error. Your GPS antenna is rarely at the bow roller. On a 30 m yacht it may be 20 m aft of where the anchor goes down.
- Look. Clear water, polarised glasses, a drop camera or a crew member in the water with a mask. The eye confirms; the map suggests.
- Record. Note the position, depth and chain out in the log. If challenged, you want evidence of a planned, careful anchoring.
CAUTION — Private apps and chart plotters Commercial charts and plotter overlays may show seagrass, but they are not listed as official tools. Use them if they help, but check against an official source before you rely on them.
The paper chart
Art. 3.4 of Decreto 25/2018 says the cartography will be put into systems accessible to navigators and, where possible, onto nautical charts. Do not assume your chart already shows meadow limits; most do not show them at the detail you need for a cala.
TIP — The larger-area rule works for you too If two official sources disagree, plan for the one showing more meadow. You will lose a few metres of anchorage and gain a clean inspection.