Weatherfax | Official OpenCPN Homepage

With an internet connection it is quite easy to select the 'HF Radio Schedules' to select and set alarms for use with a reciever, or to select the Internet Schedules and then retrieve Weatherfaxes via the Internet and overlay on the chart. Audio Capture requires a connection. The plugin data directory contains an WeatherFaxInternetRetrieval.xml file that has database for meterological sites. The 'Internet Retrieval' Option uses this schedule. It is a wonderful planning tool for cruises or passagemaking. There are several options, but first Select 'Internet' to retrieve HF Radio Schedules via the internet. Then Select 'NOAA' Under 'Servers' you will see 'Stations' fill up. Then select 'Boston' and the Internet Retrieval choices are automatically listed in the menu area. Select several faxes and pick 'Retrieve Scheduled' or 'Retrieve Selected'. The weatherfax will be overlayed generally in the proper location provided the weather service has not changed their fax formats. (The user can modify the associated WeatherFaxInternetRetrieval.xml file appropriately to add or modify the actions.) Users should please post changes to this file to the Weatherfax Thread for the next release. The plugin has a builtin database (WeatherFaxSchedules.xml) for HF Radio Weather Service Fax transmissions, which when used properly can automatically alert the user and begin decoding these faxes. A line from the ssb radio to the audio input of the sound card should be attached, and the radio tuned to the appropriate frequency (1.9khz below listed frequency and SSB mode) The SSB BFO must be adjusted correctly. The images decoded can then be calibrated and overlayed on charts. The resulting image can be exported to a chart, so the plugin also works as a general purpose conversion tool to make charts from images. The plugin can read and open numerous common image files, and audio files, and can save Kap files. The next step in development is to have it read Kap for ease of use with respect to coordinates being recorded and reused. Then from the main screen select the Weatherfax Icon, a window pops up. Select Open and browse the FaxWx directory and select a fax file. If the fax is a Mercator projection (orthogonal, not polar), click through the next screen that comes up and at the second screen set the coordinates and lat/long properly. (Screenshots will be added later) and click on through to see the fax overlaid on the charts. Note: It is very difficult to test for poor coordinate and lat/long input, so it is best to have your lat long correct, otherwise strange things may happen with the overlay in Opencpn. I first use a separate image viewer with the selected fax image, to zoom in and to write down the Lat/long and coordinates that I will be using. If you plan to export to a chart file then you should select 'Get Aspect Ratio' There are other techniques used to modify a Polar fax onto a Mercator projection chart which are reviewed on the forum and will be more fully described later. Review the posts following this Then hit Get Map, the Blue circles should follow the latitudes of respective coords. Adjust the left/right location with the PoleX value and adjust the circle radius with the PoleY value. Set the True Width Ratio value to 1.0. - Adjusts the width of the blue circles (a fraction like .8 makes the circles wider, and 1.2 makes them narrower). Adjust the true width ratio such that the blue circles align with the associated latitude lines, otherwise the 'Apply' transformation will not render straight lat/long lines or will fail. - Moves the center of the blue circles left and right. The blue circles should be centered on the vertical meridian which goes through the pole. Moves the center of the blue circles up and down. The blue circles should be centered on the pole. Hit get mapping to see how this is working, because the blue rings change in width, and sometime the ring closest to the pole flips if the value is too far out of whack. If you are starting fresh with a Polar, and the blue rings are too wide after hitting Get Mapping, first check the lat/long entered and reset coords to be sure they are hit, then Hit 'get mapping again' then adjust the 'True width ration' so the blue rings align with the latitude lines. Once that is done don't hit 'Get Mapping' again, hit 'Apply' the lines should be straight and orthogonal. Image files that are downloaded and overlaid onto charts with specific coordinates, can now be saved as Kap files that save long/lat and coordinates with the file. The next step is to have the plugin read Kap files so they can be automatically overlaid on charts without having to use the Fax Translation Wizard. Source.


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Last Modified: September 25, 2014 @ 12:00 am