The images that are included with the stock Xplanet installation are fine, but I think the beauty of Xplanet is that it can leverage more up to date, and higher resolution, images and apply various layers to make the map rendering “pop” off your screen. There are a number of websites where you can grab various images, and a small selection is on the Links page.
Xplanet does a great job of normalizing the layers of map images to your screen ratio regardless of whether the -geometry option is defined. I try to use high quality map images that do not take up more than 10 MB without a care to the image dimensions. Xplanet will spend a bit more time – we’re talking about a few seconds – normalizing the dimensions, but the output is a high quality image when it renders the map.
This way will only draw the image to the primary monitor and does not save it. The next update will render a new drawn image. If you want to save the output, you will have to use the -geometry option.
For this reason, I also do not convert the layers using ImageMagick to a uniform screen ratio. I feel like the image loses too much in translation during this process. Less is more. Xplanet is the only program that touches the images.
NASAs Blue Marble Next Generation site, bar-none, has the most complete, up to date, and highest quality images on the Internet. We’re going to get our physical Earth maps, night time map, and bump map from here. For all the maps, download your preferred resolution to ~/.xplanet/personal/images.
Earth (Land) Maps
The Earth, obviously, forever changes and has its own cycles, yearly and otherwise. Instead of using a static image of the Earth representing its geography, I prefer to show Earth going through its yearly cycle. Blue Marble Next Generation has three pages dedicated to Earth’s monthly imagery. You can sense the Earth inhaling and exhaling as you cycle through the monthly images. The seasonal changes to the land through the greening and browning periods and the incoming and outgoing snow line shows us that Earth is very much alive.
Each month has three types of images: the monthly composite, the monthly composite with topographical information, and the monthly composite with topographical and bathymetric information. Choose a specific type and download the monthly images or download all 36 images to experiment.
Night Time Maps (City Lights)
The night time map represents, more than any other map, the story of us. The other maps tell the story of the Earth through its geology and its relationship with the Sun and the Moon. The night time map tells our story – encapsulating our intended and unintended development – in an image that shows how we have adapted to control our place.
There are two maps from Blue Marble that I am partial to:
- Night Lights 2012 – Image using data gathered from 2012 using more advanced imaging techniques.
- Earth’s City Lights – Image using data from Oct 1994 through Mar 1995. The brightest areas are the most urbanized, and not necessarily the most populated. I prefer this map because I think it shows better, e.g., the outline of the Trans-Siberian railway and the Nile River are more apparent. Even China from 20 years ago is better highlighted in this image.
Xplanet uses a bump map to use for relief shading. A bump map is nothing more than a topographical map representing the elevation of the Earth’s land surface relative to sea-level. Positive values indicate a height above sea-level; negative values indicate a height below sea-level. This map adds an additional layer that to the final rendered image that provides a pop, literally because it represents the Earth’s topography. This is the last map we need from the Next Generation catalog.
Xplanet uses specular maps to display the reflection of the sun off the oceans. Adding this layer to the final image provides an additional realistic aspect as the Sun lights the Earth.
The specular map from Celestia Motherlode is the best I’ve seen. The map came as a series of 512×512 images that I organized and stitched together using ImageMagick’s montage function. You can download Celestia’s specular map and stitch it together yourself or you can download my complete stitched image here (16,384 x 8,192 / 10.4 MB).
Similar to the night time map, the cloud map provides a sense of the present. One can appreciate the size and scale of ocean storms approaching landfall especially as we continue to personalize Xplanet with marker files.
Here are three maps I’ve used:
- Blue Marble Clouds – High quality image, but static. This image will not realistically represent current weather patterns.
- XplanetClouds Free Daily Map – Hari generates a daily global cloud map using GOES, METEOSAT, and GMS satellite information. These are neither real snapshots nor accurate; neither calibrated nor geolocated. They are to make the earth look pretty.
- XplanetClouds Subscription – You can also subscribe to receive higher quality images from Hari’s site. These cloud maps are updated every three hours and are near real-time. The benefit of subscribing is that the cloud formations accurately track to storms, typhoons, and hurricanes in real-time.
If you enjoy what Xplanet provides, splurge for a yearly cloud map subscription at your preferred resolution. It does make a difference in the rendered image.
If you want to use the Blue Marble static cloud image, then go ahead and download that now. Otherwise, skip downloading the cloud map.
Linking the Static Maps
We’re not going to link all the maps, just the truly static ones that do not change with any frequency: the night light map, the bump map, and the specular map. Set whatever is in between the “[” and “]” specifically for your environment.
cd ~/.xplanet/images ln -s ../personal/images/[NIGHT MAP] [NIGHT MAP ALIAS] ln -s ../personal/images/[BUMP MAP] [BUMP MAP ALIAS] ln -s ../personal/images/[SPECULAR MAP] [SPECULAR MAP ALIAS]
I create the symlinks because I like having all the images in one central location. This becomes more apparent as we have to cycle through the monthly Earth images. Using a symlink is one way to have Xplanet use the correct image without having to restart Xplanet. I can also update the symlinks to experiment with other map images without having to restart Xplanet.
Either way, you can actually place these three maps into the above directory if you prefer. The downside being you will have to bounce Xplanet if one of the images defined in the config file changes.