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Up to date light pollution map?

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#1 NG98

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Posted 07 May 2013 - 06:00 PM

I know there is the Dark Sky Finder, but that is several years old. Anyone know of a new, up to date light pollution map?

#2 jchaller

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Posted 08 May 2013 - 02:32 AM

Cloudy Nights member DaveL (David Lorenz) produced an updated map to more accurately reflected North America light pollution. You can take that map or the original and us them as overlay(s) with Google Earth.

Sky&Telescope article:
http://www.skyandtel...s/98470604.html

See link below for maps:

http://www.lightpoll.../pages/fig2.htm

https://sites.google...light-pollution

#3 REC

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Posted 08 May 2013 - 07:33 AM

This is interesting. Seems I'm right on the boarder of a red-orange zone. Red to the east and orange to the west. Street lights in the front of my house facing west and no lights in back facing east.

I need to take a SQM reading to see how it compares to your reading.

Bob

#4 derangedhermit

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Posted 13 May 2013 - 01:23 PM

Hi, 3DaveL's work was with 2001 data from the DMSP satellite.

There is now a replacement satellite, Suomi NPP, with a better instrument, VIIRS. The image "City Lights" of the lower 48 was created in 2012 US City Lights 2012 . I have asked DaveL by e-mail (3DavdL@gmail.com) if he will run his software using the new image data, but have not heard back from him.

I would very much like to see a new version of the "Brightness of the Night Sky" maps using current, higher resolution data, and without the restrictions on distribution and non-commercial use placed on the images from Italy.

The algorithms used to transform the city lights image data to a sky brightness map are non-trivial, and Dave has implemented them independently, based on the original research. I think Dave is in an ideal position to give the entire amateur astronomy and light-pollution communities an important gift, if we can reach him.

Perhaps someone with more influence could try to get in touch with him, or we could mount a community effort, or something - ideally, so he could make updated maps, or at leats release the existing source code so other people can take advantage of the great work already done. The last update I see on the web site is 2011, where he corrected a mistake in the 2001 maps.

Tony Flanders featured him in an article - maybe that is one way to reach him. Maybe someone knows him personally.

What can we do?

#5 Tony Flanders

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Posted 13 May 2013 - 01:43 PM

There is now a replacement satellite, Suomi NPP, with a better instrument, VIIRS.


Sadly, better isn't the same. Using a different instrument means that it may be very hard to calibrate the two sets of measurements against each other, which is necessary to discern long-term changes.

There was an issue with DMSP with saturation of sensors from bright urban areas; I don't know if that's true for VIIRS as well.

I would very much like to see a new version of the "Brightness of the Night Sky" maps using current, higher resolution data, and without the restrictions on distribution and non-commercial use placed on the images from Italy.


Given the inevitable crudeness of the raw data, I think the resolution of the original atlas was just fine. You have to realize that upwelling light detected by satellites is just a proxy for actual light pollution. A spotlight pointed up looks bright to a satellite and generates little skyglow. The same spotlight pointed horizontally is invisible to a satellite and generates lots of skyglow.

As for rights, the old Light Pollution Institute was disbanded, and last I asked him, Cinzano was happy for anybody to use his data.

#6 derangedhermit

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Posted 13 May 2013 - 11:26 PM

There is now a replacement satellite, Suomi NPP, with a better instrument, VIIRS.


Sadly, better isn't the same. Using a different instrument means that it may be very hard to calibrate the two sets of measurements against each other, which is necessary to discern long-term changes.

There was an issue with DMSP with saturation of sensors from bright urban areas; I don't know if that's true for VIIRS as well.


Yes, it may be hard to determine long-term changes. But determining long term changes may not be the only thing of significant value to come from using current data. Having a map that more accurately reflects today's situation is of real value to many people.

I am aware they made a number of special passes to deal with saturated pixels on the old instrument. I don't know about the new instrument either, but one can be optimistic that they have carried forward a way of controlling exposure. The "City Lights" image, however photoshopped it might be, is reasonably exposed.

I would very much like to see a new version of the "Brightness of the Night Sky" maps using current, higher resolution data, and without the restrictions on distribution and non-commercial use placed on the images from Italy.


Given the inevitable crudeness of the raw data, I think the resolution of the original atlas was just fine. You have to realize that upwelling light detected by satellites is just a proxy for actual light pollution. A spotlight pointed up looks bright to a satellite and generates little skyglow. The same spotlight pointed horizontally is invisible to a satellite and generates lots of skyglow.

The technology certainly exists to identify streetlights and other individual sources, so I disagree about "inevitable crudeness of the raw data."

You have to realize that an imaging device on a satellite need not be pointed straight down. I did manage to comprehend it was a proxy.

As for rights, the old Light Pollution Institute was disbanded, and last I asked him, Cinzano was happy for anybody to use his data.


Then the official project web page should be updated. One would be foolish to use copyrighted data based on the verbal approval of one of the holders, while there were still public written statements to the contrary. Since you correspond with him, how about asking him for the source code?

#7 vsteblina

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Posted 13 May 2013 - 11:48 PM



Given the inevitable crudeness of the raw data, I think the resolution of the original atlas was just fine. You have to realize that upwelling light detected by satellites is just a proxy for actual light pollution. A spotlight pointed up looks bright to a satellite and generates little skyglow. The same spotlight pointed horizontally is invisible to a satellite and generates lots of skyglow.
[/quote]

Hi Tony,

I retired from the Forest Service. I had responsibilities for Wilderness on a large National Forest.

One of the issues in Wilderness is a pristine night sky. The National Park Service is taking the lead in this area.

On one of the astronomy forums a guy was modeling various effects of light pollution. I asked him to generate me a map of the United States that showed areas with "no skyglow visible from light pollution".

Excluding the effect of topography...there were NO areas east of the Mississippi River without skyglow visible.

The shock, however, was how few areas in the western US were without skyglow.

I lost track of the persons name, however, it should be fairly easy to reconstruct using GIS.

It is a interesting map that really shows the extent of light pollution in this country.

#8 Tony Flanders

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Posted 14 May 2013 - 04:11 AM

I asked him to generate me a map of the United States that showed areas with "no skyglow visible from light pollution".


That's an extremely stringent condition. The only places I have been with no visible artifical skyglow are ones where much of the horizon is blocked. I doubt there's anywhere in the Lower 48 with completely unobstructed horizons where there is no visible artificial skyglow at all.

From a typical mountaintop you can see 100 miles in all directions. Not a single light bulb or automobile headlight within a 200-mile-diameter circle? I doubt it!

However, I have been to plenty of places where there's no significant artifical skyglow -- just a few small glows in a few directions, much less obtrusive than the common faint aurora seen in north over much of the U.S.

#9 vsteblina

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Posted 14 May 2013 - 10:19 AM

Northern Nevada and south-eastern Oregon were really the only large areas without skyglow. The effects of topography were excluded so the map reflected a flat earth.

Having been gone north to south in Nevada on Highway 93 that area probably has ZERO sky glow.

I believe the base map was the early or late 1990's.






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