The GRIB files in GPSNavX and MacENC

Menu Weather in these two applications can make a request from a GRIB file weather forecasts and then see it on the open map. Function Request GRIB sends a request to the server Saildocs.com returning to the mailbox file requested. You can then get the file in attachment and store it to the location of your choice (²).

Function Show GRIB will then see the file on the card and scroll forecasts. You may also want to refer to Video tutorial MacENC No. 3 on the website.

Here is a short technical summary of the weather module integrated in these two apps.

Types of data

You can choose from several types of data :

  • Surface wind and Pressure
  • Surface 500 mb
  • Waves (Height & Direction)
  • Water temperature
  • Air temperature
  • Precipitation rate

In GPSNavX : Forecasts are provided by intervals of 12 hours out to 3 days. The files cover a 50 ° x 50 ° area, corresponding to the chart displayed at the request (Minimum Scale 1/750.000).

In MacENC : Three sub-menus allow you to define the characteristics of files :

  • Out to : 3, 5 or 7 days
  • Intervals : 3, 6, 12 or 24 hours
  • Resolution (grid) : 0,5°, 1,0° or 2.0 °
These choices depend on the size of downloaded files and thus the cost of transmission (i.e.. Satellite phone).
The files cover a 50 ° x 50 ° area, but the function Reduced area, if checked, reduces the area 20 ° x 20 °, to limit the size of the file.

What forecasting models ?

All prediction come from GFS 0,5° NOAA unless the waves from the model WW3 1,0° (¹).

However, since version 8.10, MacENC adds a Surface wind / pressure request with high-resolution model COAMPS from the U.S.. Navy (¹), with a resolution of 0.2 ° (12 NM) by 6 hours step up to 48 hours, and exclusively for the three areas below :

 

zones US COAMPS

U.S. Areas. COAMPS

Notes :

MacENC uses the mail protocol as many yachtmen use the email wireless service XGate with a satellite phone at sea to download GRIB files. This is also valid for other providers (Vizada, Geolink, MailaSail) Otherwise, The advantage of using an email connection is the support for mid file restart, in the event the sat phone connection is lost during transmission.


(¹) See " Forecast Models " in the Glossary for technical explanations.


Related Articles :
(²) Receiving GRIB files with GPSNavX MacENC
On website : Weather files 1/2

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