KenMankoff

YAGEL – Multiple Balloons on Mars

I’m releasing Yet Another Google Earth Layer, this one featuring some more KML tricks and hacks pushing Google Earth to do things that Google does not officially support: multiple placemark description balloons visible at once.

Download: Mariner Mars 1971 (MM71) Ultraviolet Spectrometer (UVS) Data in Google Earth. This is a work in progress as part of a Planetary Data Restoration Project at the Laboratory for Atmospheric and Space Physics and as such the data is not finalized and is subject to change.

The data comes from the Ultraviolet Spectrometer on the Mariner Mars 1971 spacecraft, and had previously been processed for the Albatross software tool back in 2002. Neither Google Earth nor its predecessor KeyHole, nor even KML, existed back in 2002, and the data needs to be accessible in a more modern and accessible visualization tool (Google Earth) in order to remain useful.

The footprints are where the instrument was looking. In each of these regions a spectral range from 2107 to 3497 Ångströms was sampled, and the spectra are visible in both the hacked multi-balloon display, and in the more detailed official Google Earth balloon visible by clicking on the footprint. Each footprint is colored, both in the map view and in the sidebar, by the response at 3049 Å, which is roughly where the ozone signal is. For more information on the data and science see the references listed at the end of this post.

Previously I implemented vertical data “curtains” in KML, useful for oceanographic transects, seismic lines, spacecraft looking down through the atmosphere in profile (as opposed to a 2D surface image), or any other vertical data. Along with vertical data (solved) and subsurface data (no known work-around), another major limitation of Google Earth is that only one description balloon is allowed to be visible at a time. However, Google Earth does support multiple placemarks (by default yellow pushpins in Google Earth, or red pins in Google Maps). The hack to get multiple balloons visible at once is to make custom icons that look like balloons and then use them in place of the default icons. If this technique is used it is advised to implement various other KML features to make the balloons only appear in certain views and therefore avoid overwhelming the viewer. I’ve used both the TimeStamp and the Level of Detail features to limit when the icons appear.

@article{barth1974atmosphere,
  title={{The atmosphere of Mars}},
  author={Barth, C.A.},
  journal={Annual Review of Earth and Planetary Sciences},
  volume={2},
  number={1},
  pages={333--367},
  year={1974},
  publisher={Annual Reviews}
}

@article{barth1971mariner,
  title={{Mariner 6 and 7 ultraviolet spectrometer
                   experiment: Upper atmosphere data}},
  author={Barth, CA and Hord, CW and Pearce, JB and
                 Kelly, KK and Anderson, GP and Stewart, AI},
  journal={J. geophys. Res},
  volume={76},
  year={1971}
}

Vertical Data in Google Earth

Google Earth does not officially support vertical curtains of data. However, it does support buildings with images on the side. If you are willing to stretch the definition of a building, you can put any vertical data you like into KML. This implementation was inspired by the Goddard Earth Science (GES) Data and Information Service Center (DISC) sample files for CloudSat, CALIPSO, and Aqua.

If you use IDL and would like to image your data in Google Earth, be it points, lines, regions, surface images, or vertical data, you should be using my IDL interface to the KML API.

Vertical Data in Google Earth

Earthquakes

I came across a database of earthquakes from 1960 to almost present. I converted it from the existing form to KML so it can be seen in both Google Earth and Google Maps. Both views incorporate a temporal component.

For the Google Earth view, magnitude as been encoded as pin size and depth has been encoded as height above the Earth. A few interesting regions where the deep quakes occur, such as east of the Andes, pop out.

Earthquakes

GISTEMP.StationData

NASA GISS has recently announced another year of the surface temperature trends. Last year, 2009, tied for the 2nd warmest year on record, and the past decade (January 2000 to December 2009) was the warmest on record.

I took the time this weekend to re-create a Google Earth layer showing these data. This visualization allows you to see a broad geospatial overview, and then select any particular location and see both long-term trends and even the data point for each individual month.

Download (330K)

GISTEMP.StationData

GISTEMP.StationData

KDM-IDL Code Library

I have spent quite a bit of time developing IDL code in the past, and it appears I will do some more in the near-term future. I have decided to release my IDL code library to the public so that others can perhaps benefit from my work. This is a work-in-progress and access is via Subversion.

One subset of the library is the KDM_KML lib for writing KML files. This code should make it fairly simple to display data sets in Google Earth from IDL.

I have currently implemented about 50% of the KML API and will get the rest implemented as time goes on. Right now layers can have overlays, points (placemarks), or linestrings (paths). Any element (that the API supports) can have a timestamp, and styles are supported too. With knowledge of the KML API you can create artistic balloons with whatever content you like that can even link to each other.