Greetings Mission Planners,
The past few months have seen a constant stream of vulnerabilities identified in Microsoft's Internet Explorer (IE) web browser. The U.S. Computer Emergency Readiness Team (CERT) has taken the amazing step of recommending "Use a different web browser":
There are a number of significant vulnerabilities in technologies relating to the IE domain/zone security model, the DHTML object model, MIME type determination, and ActiveX. It is possible to reduce exposure to these vulnerabilities by using a different web browser, especially when browsing untrusted sites. Such a decision may, however, reduce the functionality of sites that require IE-specific features such as DHTML, VBScript, and ActiveX. Note that using a different web browser will not remove IE from a Windows system, and other programs may invoke IE, the WebBrowser ActiveX control, or the HTML rendering engine (MSHTML).
As for me, I've had enough "Critical Updates" to last a lifetime and have switched to Mozilla's Firefox Browser. Unfortunately this isn't an option on your Government PC, but there's no reason to leave your home computer vulnerable to the "intrusion of the week." Firefox also includes tabbed browsing (easily switch between multiple web pages) and an integrated download manager to help download multiple files simultaneously. It imports all your Favorites (and your other settings) from Internet Explorer and is being constantly upgraded.
Recently errors have been discovered with the Placenames depicted on Topographic Line Map's (1:100K, 1:50K) over Afghanistan and Pakistan. These errors effect the paper chart and the CADRG equivalents. The chart series effected include U611, U622, U711 and U722. NGA is working to correct these errors and continued use of these charts is approved, but use the Geographic Names with caution!!! New(er) editions with corrected names should be available (in both paper and digital versions) shortly.
I've posted a new version of Excel2FV Mark II on the Download page. You can now export Manual CHUM towers to an Excel Spreadsheet. I've also made a change to how new Drawing and Local Point files are created that may let the Excel2FV run correctly on some machines that earlier had trouble.
Mission Planning Tip of the Week: Geographic Line Styles - Part 1
The last few years have seen a big improvement in ensuring that a point's Lat/Long location also includes the datum. The universality of WGS 84 (thanks to GPS) has also helped eliminate many coordinate errors. People are beginning to learn how important the vertical datum is for precision coordinates and starting to understand the differences between "MSL" (Mean Sea Level) and "HAE" (Height Above Ellipsoid).
After defining one point in space you'll want to connect it to a second point - but should you draw the line? The shortest path between two points is a straight line, but what the heck does that mean?
The two main line types are "Great Circle" and "Rhumb". A Great Circle line is the shortest distance between two points, but the true heading will vary along the line. A Rhumb line has a constant true heading but at the cost of a longer path. The images below show a Rhumb line (red) and a Great Circle line (green) connecting McChord AFB (KTCM) with Hurlburt Field (KHRT):
In the first image shows an Equal Arc projection and the Rhumb line is the "straight line". The second image shows a Lambert Conformal Conic projection and now the Great Circle line is straight. The images below show the lines as they depart McChord and arrive at Hurlburt:
The headings greatest divergence is at the beginning and end of the line segments, but the greatest cross track occurs midline where the lines are parallel. The image below shows the two lines separated by nearly 100NM near the Colorado/Nebraska border:
With two such widely divergent tracks you'd expect to see a significant difference in distance, but you won't. The Rhumb line track is 1,941 NM and the Great Circle line is 1,931 NM. The moral here is if you're on a long flight and suspect you'll have to divert for weather then you're better off diverting early, staying well clear and maintaining a straight path. The total distance won't change too much.
PFPS Routes
PFPS 3.1 added support for route calculation/display of different line types. The PFPS Premission dialog lets you switch between Great Circle and Rhumb. PFPS uses Great Circle lines by default - the standard for IFR RNAV flight.
Line Styles in FalconView
FalconView 3.2 was the first version to add support for different line styles for items other than PFPS Routes. Not surprisingly, FalconView 3.2 was the first version to add support for different display/print projections. FalconView supports DAFIF, Drawing and Range & Bearing line styles. FalconView has a third nonstandard line style called "Simple Line". A Simple line is a straight line on the computer screen or printout no matter what chart projection is used. New Drawing lines are Simple lines unless you adjust that line's properties.
Next time I'll talk about how Line Styles are handled in DAFIF, Airspace Control Orders (ACO's) and Shapefiles.
Paul