XTide vs Marine Barometer

XTide provides tide and current predictions. The Apple Watch app and Widget show information for the closest of your favorite tide stations. It is based on the popular open source XTide for Unix from http://www.flaterco.com/xtide/introduction.html XTide includes a harmonics file (tide data) for the United States only due to legal issues with the data from other countries, but supports custom harmonics files. See https://flaterco.com/xtide/faq.html#60 for more information. NOT FOR NAVIGATION This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. The author assumes no liability for damages arising from use of this program OR of any 'harmonics data' that might be distributed with it. For details, see the appended GNU General Public License. (Accurate tide predictions can only be made if the 'harmonics data' for the relevant location are good. Unfortunately, the only way the maintainer of those data has of knowing when they are bad is when someone with access to authoritative tide predictions or observations reports a problem. You should not use this program or any data files that might be distributed with it if anyone or anything could come to harm as a result of an incorrect tide prediction. NOAA and similar agencies in other countries can provide you with certified tide predictions if that is what you need.) XTide's predictions do not incorporate the effects of tropical storms, El Niño, seismic events, subsidence, uplift, or changes in global sea level.

Marine Barometer is a barometer sensor interface that is uniquely designed to meet the needs of mariners who rely on accurate atmospheric pressure for weather routing and the evaluation of weather maps. Pressure readings can be manually saved permanently along with the latitude, longitude, and time of the reading. If a sensor offset has been applied, that value is also stored with each recorded pressure. These recorded pressures can then at the navigator's convenience be transferred to the vessel's printed logbook. The GPS sensor is accessed for latitude and longitude only. The elevation of the sensor (your iOS device that includes a barometer) above sea level must be entered manually. Elevation values from the GPS are not accurate enough for the intended application. The concept of sea level pressure is explained along with how it is determined from the sensor reading. Instructions are provided on how to check the calibration of the sensor, and a sensor offset can be applied as needed. Links to sources of accurate sea level pressure are included. Sources of accurate elevation are included for use on land. The standard units for marine applications are millibars (mb) or hectoPascals (hPa). The main pressure display can also be set to inches of mercury, millimeters of mercury, or kiloPascals. However, because the primary reference pressures that would be used to check the sensor calibration are in mb, the sensor calibration must be set using millibar units. Reference links are provided for learning more about the tactical use of pressure for weather forecasting and weather map evaluation. Discounts are offered for barometer related reference books.