Monday, August 20, 2018

Timelapse video of conversion of lamps from HPS to LED in Innsbruck

Christoph Malin sent me this video quite a while ago, and I have been meaning to post it to the blog for ages. Check out his time lapse showing the same streets in Innsbruck, Austria lit with HPS and LED lights.

Christoph is a photographer and cinematographer. You can follow him on twitter.

Wednesday, August 15, 2018

Luojia-1, a new night imaging cubesat

This week I had a visit from Xi Li, a professor at Wuhan University in China. Among many other things, we discussed the Luojia-1 cubesat which was designed by Wuhan University and launched several months ago. The satellite is already providing exciting imagery from a number of locations around the world. For example, compare the image of Berlin from the DNB monthly composite (left) to the Luojia-1 image (right) below.

Two images of Berlin at different resolutions. Tegel airport is at top left,
Schoenefeld/Berlin Brandenburg International airport is at bottom right.

Luojia-1 takes images at a resolution of about 130 meters, a major improvement over the ~750 meter resolution of the DNB. The higher resolution makes it possible to see smaller features, such as the major road network of cities or individual bright large buildings. The downside of high resolution is that Luojia-1 can only take images of smaller areas, rather than imaging the entire world the way DNB does each night.

In the coming years, Luojia-1will create a map of light emissions for the entire country of China. It will also acquire images of a number of cities worldwide, and will be tasked to take images of some areas for humanitarian regions, such as to provide information about infrastructure damage in war zones or overview of areas experiencing wildfires.

The data acquired by Luojia-1 is made freely available a short time after it has been transmitted to Earth. The data is not yet radiometrically calibrated, but it is already georeferenced. (Note: in some of the photos from June, I noticed some relatively large errors in the georeferencing.In images from July, the error is typically only a few pixels).

The team from Wuhan University has already produced a web portal to allow everyone to discover and download the data.When you go to the site, a login screen will appear with the public login information already filled in. Click up at the top right to change the interface to English and log in.

From the next page, you can use a tool to draw a polygon to select your region of interest and check whether imagery is available. Keep in mind that the satellite has only been acquiring data for a few months, and because it is a cubesat the total bandwidth available for downloading data is limited.

I am looking forward to seeing the interesting results that come out of this new data source (as well as the data from another upcoming cubesat from the Adler Planetarium in Chicago)! If you have questions about the data or would like to request imagery for a specific location, contact Xi Li.


Update 2022/06/06: Nicholas, for some reason Google isn't letting me reply to your comment below, so I'm adding a line here. I'm not sure what your units are (e.g. nW/cm^2sr or W/m^2sr), and in any case I'm not quite sure what sort of typical values one should expect from Luojia one. You may wish to contact Xi Li.