March 17, 2011
Most raster charts for marine use are created in a convenient and universally accepted Mercator projection. Mercator projection allows charts to be “quilted” (or connected together on a world-wide view). However, some raster charts still use other projections for reasons of convenience, tradition, data availability etc.
These charts can’t be directly “quilted” with the rest of Mercator-based “world”.
In US, NOAA uses non-Mercator, primarily Polyconic projection raster charts, for coverage of Great Lakes area. Polyconic was a predominant projection for US charts from mid-1800s to early 20th century.
To fit non-Mercator chart into Mercator world, it needs to be re-projected, that is – chart image needs to be transformed to match Mercator projection requirements.
While differences may not be as clearly visible on a large scale (small area) chart, small scale charts are very telling. Here is an example of small scale chart (NOAA 14500, Great Lakes overview) in original Polyconic and reprojected Mercator.
Note how parallels and meridians are not perpendicular on the Polyconic projection chart above and intersect under 90 degree angle on the Mercator chart below. Mercator projection is conformal, i.e. – able to preserve angles and courses, including those between latitude and longitude lines.
Chart reprojection is available in current release of PolarView NS.
December 31, 2010
Dear Polar Navy users, friends and chance visitors to this blog!
I’d like to wish you a happy, peaceful and successful new year! Let your routes be free of trouble, your arrivals timely and let wind be always in your sails wherever you may go!
November 26, 2010
NOAA is getting with the times and now you can find out about NOAA chart updates on Twitter here: http://twitter.com/nauticalcharts
PolarView users can download and update NOAA charts directly from the program. Just follow these step by step instructions:
1. Open “Download” dialog by selecting “File-> Chart Download” menu or using keyboard shortcut Ctrl + ‘D’ (Windows) or Cmd + ‘D’ (Mac).
2. Press “Select” button to select area on screen.
3. Click on the first point on a chart. A yellow selector box should appear. Move the mouse to resize selector. Click on a chart again to stop resizing selector box and finalize selection.
4. In “Download” dialog click “Find Charts”. A new window should open, as shown in the image below, presenting you with a choice of available ENC charts for selected area.
Chart in the list will have different color depending on current status, also shown in status column. Charts that are up to date will be shown in blue. Charts that are out of date and have newer version available, will be shown in red. Charts that have not been previously downloaded will be shown in black.
5. Select charts you would like to download or update. To select a block of charts, click on the first entry, scroll and Shift-click on the last chart entry. To select multiple individual charts use Ctrl + click (Windows) or Cmd + click (Mac).
To update existing charts, sort by “Status” column by clicking on column heading. Once sorted by status, you can select only those charts that are out of date or not installed.
6. Press “Download” button to download and install selected charts.
That’s all there is to it 🙂
Chart Update Window
November 13, 2010
It’s been quiet on this blog for a while, but not for lack of development. I am working on a number of new features for the next release (probably early next year, though specific timeframe may change).
One issue that many users commented on, and which was neglected until now is chart information display. While S57 chart info displayed by PolarView was comprehensive, it was not particularly easy to read.
This is finally changing now. A new chart info display is under development. It will combine most important data in a single screen, while omitting more technical items (such as what scale to show a given object at). An “old style” comprehensive list will continue to be available, selected as a configuration option.
Here is a screen capture of what a new chart information dialog may look like.
New vector chart info
I found that with this display I am constantly surprised by how much information is in S57 vector charts, much of it unnoticed previously.
That said, this is work in progress and I am interested in your feedback. What do you like about it? What would you change or improve? What would be good extensions to this display to consider in the future?
June 2, 2010
Below are a few videos demonstrating some of the basic functionality of PolarView. I did not spend much time on it so quality is not great. I still need to figure out how to annotate mouse clicks and keystrokes.
Some of the features in the video are not yet available in the current release – but will be in the upcoming version.
Demonstrating how to lay a route:
Miscellaneous options including:
– Setting and moving a waypoint
– Changing palette colors
– Showing tide information for a given tide station
– Searching chart list for a specific chart
Using a GRIB viewer:
A better demonstration of a GRIB viewer (using an older version of PolarView), made by a user. Thank you!