Info from USGS about the Badwater low point

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Candace_66
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Info from USGS about the Badwater low point

Post by Candace_66 » Wed Jan 21, 2015 4:14 pm

Recently, I emailed the USGS to inquire about the coordinates of the low point in Badwater Basin, and if the USGS has ever monumented (i.e., placed a benchmark or something) at the spot. Here's the response I received:
Thank you for contacting AskUSGS.

There are a number of benchmarks throughout the valley set by the National Geodetic Survey (NGS) although apparently not one marking an actual lowest point. The run of markers were placed along the western edge of the valley.

The lowest monumented elevation we could identify using the NGS Data Explorer ( http://www.ngs.noaa.gov/NGSDataExplorer/ ) is -273.48 ft. A link to the datasheet is below.

That marker is in the Devils Golf Course, north of the Badwater Basin where the lowest point would be. It is likely that one very good reason for not locating a marker there is the salt flats would be very corrosive to any concrete and metal structure and it would probably disintegrate very quickly. Note the statement in the datasheet on the condition of that marker. Also, an absolute permanent lowest point would likely not be possible as shifting in the salt flats occur through natural processes.

NGS Datasheet H 680: http://www.ngs.noaa.gov/cgi-bin/ds_mark ... Box=GS0240

According to current elevation data, there is a slight depression, west of the Badwater parking area. Elevations determined using the spot elevation tool in The National Map Viewer ( http://viewer.nationalmap.gov/viewer/ )show -281 ft in the depression, while the majority of the basin seems to average about -278. See the attached screenshots from TNM Viewer.

If there is any official monumentation, Death Valley National Park may be responsible for placement. If you haven't already, you may want to contact them.
First, I tried using the NGS Data Explorer to locate the benchmark (in Devils Golf Course) that they mentioned. I couldn't find it there. But it is shown on the 1952 Furnace Creek 15' topo map.

As the datasheet they linked shows, you're wasting your time if you go looking for that benchmark: Though it was only set in 1942, by 1949 it was already in very bad shape, and by 1983 it could not be found.

I spent a little time playing with the National Map Viewer. As they noted, it shows a depresssion out in the basin. After a lot of clicking, I confirmed that the lowest point(s) you can find using this tool is -281 feet. Below are a couple of screencaps showing what If found:

Image

Image

Using that Map Viewer, I navigated to the coordinates I had (and that others have used) for the -282 foot point. These coordinates come from the point shown on the 1986 Badwater 7.5' topo. Specifically, the coordinates I have are:

N 36 14 31
W 116 49 32
(WGS 84)

According to the Map Viewer, the elevation at that point (or at least, as close as I could navigate to that point in the viewer) is -279 feet:

Image

Ultimately, their take on the situation appears to be summed up in one of the sentences in their email: "...an absolute permanent lowest point would likely not be possible as shifting in the salt flats occur through natural processes."

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wbdeford
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Post by wbdeford » Wed Jan 21, 2015 4:39 pm

Good stuff, Candace. The coordinates you give match where I went and found this, April 2013:

http://bcdef.us/2013HikeAThon/Hikes/Hik ... age004.jpg

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wbdeford
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Post by wbdeford » Wed Jan 21, 2015 4:48 pm

If you look at the topo map, you see the marked -282 is pretty much smack in the middle of the area surrounded by the -280 contour line.....I wonder if there was no other reason than that to mark that spot as -282, knowing that the absolute bottom shifts anyway.

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Post by gedstrom » Wed Jan 21, 2015 8:51 pm

The extreme rains we had during the winter of 2004/2005 could have redistributed significant amounts salt deposits, changing what was considered the low spot. It is such a broad, flat area that it would be extremely difficult to determine what is absolutely the lowest point when the most variation you are going to find is only a foot or so in elevation. Quite a bit different than locating the highest point on Telescope Peak!

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Post by AndyR » Thu Jan 22, 2015 9:00 am

AFAIK the USGS discontinued their 'sink/tilt' experiments to determine the rate at which the valley floor was moving back in the early 60s, so who knows what the real 'lowest point' is now.

I wonder when the last official survey was?

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Post by Inyo » Thu Jan 22, 2015 10:59 am

AndyR wrote:AFAIK the USGS discontinued their 'sink/tilt' experiments to determine the rate at which the valley floor was moving back in the early 60s, so who knows what the real 'lowest point' is now.

I wonder when the last official survey was?
According to Google Earth, the last satellite fly-by over Badwater Basin recorded for the program was October 14, 2011.

I pulled up Google Earth and manipulated the probe in places west of the Badwater parking lot. Didn't spend a lot of time with the searchings/probings, but the lowest elevation I located was a minus 281 at the following coordinates:

36 13 57.11N
116 48 06.81W

http://inyo.coffeecup.com/site/dv/dvfossils.htm
My page: "Fossils In Death Valley National Park"

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Post by MojaveGeek » Thu Jan 22, 2015 6:55 pm

USGS is a much stronger source for elevation data than Google Earth. I doubt Google is doing anything more than mapping the sat image over elevation contours from the USGS topos.

With some interpolation which sometimes is spot on and other times is a bit loose.

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Post by Inyo » Fri Jan 23, 2015 7:01 pm

MojaveGeek wrote:USGS is a much stronger source for elevation data than Google Earth. I doubt Google is doing anything more than mapping the sat image over elevation contours from the USGS topos.

With some interpolation which sometimes is spot on and other times is a bit loose.
Huh?

Google Earth uses digital elevation model (DEM) data collected by NASA's Shuttle Radar Topography Mission (SRTM)--and, the DEM is the same system the USGS uses.

Note, too, that even if one accepted the premise that Google Earth used USGS topos for elevations, then Google Earth elevation readings remain as accurate as the USGS data.

http://inyo.coffeecup.com/site/dv/badwaterviews.html
My page: Two views from Badwater.

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Post by D.A. Wright » Sat Jan 24, 2015 12:58 pm

It is my hunch that if you read between the lines of the USGS answer, that indeed the absolute lowest point is not a fixed elevation, but changeable. If anything, the lowest elevation might be slowly rising, due to disolving salts and what is washed down from the mountains. Add the deep and widespread floodwaters of the spring of 2005, shake and stir, some leveling has probably taken place.
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Post by hwstock » Sat Jan 24, 2015 4:27 pm

n 2004, GE said they would begin using satellite data. But in 4 cases I've checked where the USGS had clearly incorrect data, GE had the exact same mistakes. An example:
http://hwstock.org/picacho13/

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Post by Candace_66 » Mon Jan 26, 2015 3:21 pm

wbdeford wrote:Good stuff, Candace. The coordinates you give match where I went and found this, April 2013:

http://bcdef.us/2013HikeAThon/Hikes/Hik ... age004.jpg
I saw that "benchmark" in December 2007, and again in April 2010, and you saw it three years after that. I wonder if it's still out there?!

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wbdeford
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Post by wbdeford » Mon Jan 26, 2015 3:36 pm

I might find out this April. I like the quiet and solitude of the middle of the valley--just depends on whether I have time and energy for the 6+ mile trek.

Are you sure it is the same marker? It looks a bit different than pics I had previously seen on the internet. For example, Steve Hall's from 2008:

http://www.panamintcity.com/basin/lowestpoint.html
Candace_66 wrote:
wbdeford wrote:Good stuff, Candace. The coordinates you give match where I went and found this, April 2013:

http://bcdef.us/2013HikeAThon/Hikes/Hik ... age004.jpg
I saw that "benchmark" in December 2007, and again in April 2010, and you saw it three years after that. I wonder if it's still out there?!

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