Xearth for Windows

User Reviews

• An old but still excellent and free desktop program.

  Irritated_UserJanuary 25, 2012

  Pros

  To begin, Xearth is open source freeware! Xearth is capable of displaying many realistic and accurate views of earth on one's desktop. These views dynamically update every few minutes in line with the earth's rotation and the way sunlight falls upon the earth's surface. There are many user-adjustable settings to allow for a user's many interests and circumstances in this wonderful, long-established, classic program.

  Cons

  Xearth is now quite old, it's a port from an even older UNIX version which has its origins back in the late 1980s in an era when PC hardware was much less advanced than it is today, especially so the graphics display. Thus, Xearth needs to be updated with better, more colorful and more varied maps of earth in keeping with modern contemporary graphics cards. Furthermore, these maps should be enhanced with dynamically changing physical information such as the weather, volcanic activity etc.. Also, Xearth's existing dynamically-updating earthquake display needs updating and further enhancement. In the following summary view, I've provided a much more detailed narrative of Xearth together with its limitations and I offer suggestions as to how the program could be further enhanced and developed.

  Summary

  Xearth is a wonderful program. However it's a great pity it's so rarely updated, for with a few tweaks and some additional 'earth parameters' it'd have the potential to be much greater. Shame it languishes without these extras as it's potentially an excellent program to get kids interested in earth sciences. Xearth has been around for a very long time, in fact so long that I first encountered it in a version ported from UNIX to OS/2 sometime around 1990, but as with so many open source and freeware programs, there's little incentive for the developer to keep on developing it. It seems the original developers, Kirk Johnson and others are now out of the picture but it's still being kept alive by Greg Hewgill who originally ported it to MS Windows, and for that we need to congratulate him. Xearth provides the PC user with desktop background images of the earth that dynamically change throughout the day to reflect where the sun is shining on it at any given time. In the map of earth, land features are depicted as bright green and sea as bright blue during daytime, these fade to very dark green and blue respectfully at nighttime. Various user-selectable projections of the earth are available which include the common and well known orthographic (globe/3D), Mercator and cylindrical views. The user can define such parameters as the latitude and longitude of his/her location, which has the effect of focusing that position in the foreground, and this is especially important for the orthographic/3D globe view if say the user wants to guarantee that his/her location is always in view. For example, it's obvious the hometowns of those living in Sydney, Australia or Wellington, New Zealand would always be out of view whilst latitude 51° 28' 38" and longitude 0° 0' 0" (Greenwich, UK) remained selected. Other 'Viewpoint' settings include 'Sun-relative', 'Orbit', 'Moon' and 'Random'. I often use 'Random' as every few minutes--whenever the earth's rotation is updated--I get a different view of the earth from a random viewpoint. The displayed size of the projections on-screen can be made bigger or smaller, the default setting is '1' which means that '0.5' halves its size and '2.0' doubles it. Allowing the earth's image size to be reduced has the advantage of reducing on-screen clutter whereas enlarging it past screen size has the effect of zooming in on and enlarging that section of earth that is in focus. These display settings are very flexible and allow for many variations so it's pretty hard to get bored with Xearth. Other settings include 'Display coordinate grids' which displays a variable number of dotted gridlines per quadrant; 'Shading' which varies the intensity ratio between night and day; 'Time' which includes a time-warp setting factor thus permitting updates faster or slower than real-time; an 'Updating interval' for updating the rotation; 'Labels' which includes major capital city names together with their Lat./Longitude as well as user-definable ones; 'Sun position', 'Display stars' and 'Star frequency' which sets Xearth's desktop background. One particularly interesting setting is 'Quakes' which retrieves on-line information about current earthquakes from the USGS (U.S. Geological Survey) site and then highlights their location on the Xearth map with a yellow circle that's proportionate in size to the earthquake's magnitude. Often I've seen these telltale circles of major earthquakes appear on my desktop many hours before there's any hint of them in the radio or TV news media. Running Xearth's 'Quakes' also gives the user a feel for how many earthquakes happen on earth and which never get widely reported. It's quite common for Xearth to display over a dozen low-magnitude quakes that have occurred over a 24-hour period and or to show large magnitude 6+ ones that have occurred on fault lines in the middle of an ocean, yet they regularly go unreported in the popular press as they've been essentially harmless. If Xearth is so good then what's wrong with it? ------------------------------------------------------------- Despite its many excellent features and the fact they mostly work well, Xearth is an old program and it's now beginning to show its age. I'll illustrate with some examples. 1. This tiny point release--the first in five years from version 1.1.1 to 1.2--is a good point to begin. The release notes (readme.txt) for v1.2 says the only change from the previous version is: "Updated the URL of the USGS data to support the new RSS feed instead of the old text page.... ...This feed reports the last 7 days of magnitude 5 or greater." Herein lies the problem. In the previous version of Xearth (v1.1.1), earthquake records were updated and displayed on a daily basis, the older (previous day's) records being simply flushed away. Moreover, the older daily feed listed ALL quakes starting from a much lower magnitude (magnitude 2.5 if I recall correctly). This new feed in v1.2 has the advantage of keeping records over seven days, which is good if say one is following a major quake in the news over a number of days. However, unfortunately, Xearth v1.2 now omits displaying all earthquakes whose magnitudes are between 2.5 and 5.0, which statistically is usually a very large percentage of them. Essentially, we either have to choose between a version of Xearth that displays all earthquakes with fine resolution over a single day or another one capable of displaying results over a week but only in a coarse format that indicates just major quakes with a magnitude of over 5; unfortunately however, we can't display both views simultaneously. Xearth needs updating so it can display both or even older historical information by accepting multiple simultaneous feeds (some of which would be used-defined--user inputted settings), and it should arbitrate between these input feeds as well as collate information from all of them. Moreover, Xearth's display should be updated to display quake rings in different contrasting colors; for example, red to indicate quakes which have occurred within 'x' hours (where 'x' is definable), yellow for those with 24 hours and orange for those which have occurred over the previous 5 days. Other options might include the ability to export or plot this data with respect to time and or geographical location or by regions of high seismic activity. 2. Xearth's green/blue map is now very dated, it lacks considerable amounts of geographical detail (mountains etc.), is not very scalable without losing much detail, doesn't have a wide color gamut or use colors usually associated with physical features as do many maps (different colors to indicate increasing mountain heights etc.). Many different map types should be available to Xearth as plug-ins, for example: geographical, diagrammatic and line types, historical maps, map overlays, satellite photographs, perhaps even Google earth views. Perhaps Xearth should even work similarly to the way Google Earth does or for it to act as a translator from a Google earth feed to a dynamic desktop image view. 3. In keeping with the need to improve the dynamic range of map features, the 'display coordinate grid' setting should have an intensity attribute for the grid's dots. Ideally, the dots would also incorporate shading to improve the 3D rendering and perhaps the dots themselves might be able to be defined as other shapes (dashes etc.) 4. Xearth needs to much better represent the physical state of the earth in a dynamic and active way. Features such as the weather, cyclones/tornadoes/typhoons, auroras, snow, tsunamis, the earth's magnetic field and magnetosphere, volcanoes and volcanic activity, tides, ocean currents, ocean ridges and depths, satellites encircling the earth, shipping lanes etc. could all be incorporated onto one's desktop as active dynamically-changing background images. All these diverse features could be incorporated into Xearth by using various third-party plug-ins, and, as with the 'Quakes' feature, made 'live' by active on-line connections to updating sites. 5. Incorporating a desktop context-sensitive management console into Xearth would permit orderly, uncluttered and systematic displays of information when many plug-ins are loaded. Above all, Xearth should continue to remain open and free in any future or enhanced form, this will ensure it is used widely, especially teachers and students. My wishful thinking aside, you should still try either Xearth versions 1.1.1 or 1.2. Old Xearth may be, but it still remains a great program in its present form.

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