[Geysers] Mapping Help

[Steven Miller]

While Mike Keller whole heartedly assisted with the Thermal Inventory project, If anyone wishes details (past this email) on how the Thermal Inventory project was performed, please contact the Spatial Analysis Center in Yellowstone.
 
Having left the park service in 2010 and having worked directly on the Thermal Inventory project for many years, I will try and address your questions.
First and for most. This was a survey project and not an end all mapping project. The Trimble GPS units used were and are far more accurate then the handheld Garmin units of today.
 
The survey points, GPS locations, were taken at the edge of the feature at the best (safest and non damaging) location. That location was where the feature was sampled for temperature and basic chemistry.
 
Accuracy:
First, picture someone standing with a GPS unit on their back with an antenna sticking above their head. For safety they always stood facing the feature. So the antenna (location being recorded) was off by a foot or so?
 
The GPS points were recorded in UTMs, meters if you will. That data was later differently corrected with respect to the nearest base station. From memory the accuracy of a group of features would be from plus or minus .15 meters to a meter. So any where inside a sphere of from .15 meter in diameter to one meter in diameter. FYI, the units allowed us to correct for the height above ground of the antenna. How accurate a location taken was is depended on the number of satellites that day, the position of the satellites, and the number of points which were gathered and averaged for a location.
Now, think of this in real world terms.
 
Go outside and put four stakes in the ground, randomly but all within eight or ten feet of each other. Draw a rough circle, oval, or odd shape around each stake with a one to two foot radius (this is your thermal feature outline). Now place a point on the edge of each thermal feature. This is your GPS point you take. Then draw two circles  around the GPS point of .15 meter and one meter. Your GPS point is anywhere inside those circles. Now stand back and look at this or better yet stand on a step ladder, look at this and think about standing in a geyser basin with a bunch of features of various sizes and spacing’s.
 
Can you now see where you can have a GPS point for one feature which is closer to another feature? Or a couple of points that are closer to each other then the features? Do you see where you can have the errors that are inherent with this survey? 
 
I would have loved to have had the time, money and equipment to really map the basins from a benchmark using a transit or laser theotolite. But we could not.
Take it for what it is. A dam good survey of many of the thermal features. 
 
Scott says:
“All this kind of stuff in mind, where is the justification for coordinates cited to 7 (seven ! ) decimal points? Strikes me as vast overkill. At Yellowstone's latitude (and with this, I'll stick to latitude because it's a bit easier), one degree of latitude is equivalent to just about 69.055 miles. That is 364,610 feet. Multiply that by 0.0000001 gives 0.0364 feet, and that means these coordinates are supposedly accurate to within a touch more than 0.43 inch. Really?”
 
Nothing reported is reported with an accuracy report. Therefore you cannot induce one at will or assume accuracy from the reported numbers. Why would one even try?
 
As I said the measurements were recorded in UTMs (plus or minus .15 to 1 meter or 6 inches to 36 inches) which were converted to Lat/long via the GIS application which reports the seven decimals. Now add human error and how one stood when collecting the point and we have what; two to five feet at BEST.
 
 To be accurate each location should be reported as a single location plus or minus some value. Or by 4 coordinates at the extremes to define an area which one can use to say the location is within that area.  


"Life is pleasant. Death is Peaceful. It is the transtion that's Troublesome." -Issac Asimov
 



From: TSBryan at aol.com
Date: Mon, 11 Nov 2013 15:17:34 -0500
To: geysers at lists.wallawalla.edu
Subject: Re: [Geysers] Mapping Help


I seem to recall that Mike Keller accompanied the SCA people during some of the mapping program. If so, maybe he can elucidate us as to just how and why certain survey positions were chosen. (Example 1: Were the coordinates always taken at [say] the southernmost extreme of a feature? Example 2: Were the coordinates always determined at some specified distance away from the edge of a feature? etc.]
 
All this kind of stuff in mind, where is the justification for coordinates cited to 7 (seven ! ) decimal points? Strikes me as vast overkill. At Yellowstone's latitude (and with this, I'll stick to latitude because it's a bit easier), one degree of latitude is equivalent to just about 69.055 miles. That is 364,610 feet. Multiply that by 0.0000001 gives 0.0364 feet, and that means these coordinates are supposedly accurate to within a touch more than 0.43 inch. Really?
 
Scott Bryan
 

In a message dated 11/11/2013 10:30:07 A.M. US Mountain Standard Tim, david.schwarz at alumni.duke.edu writes:
As a result, many of the coordinates that year were only taken within roughly the same long-distance dialing area as the feature being mapped.  Obviously, it doesn't matter how accurately the equipment pinpoints your location if you're not particularly close to what you're trying to map.
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