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NGS Webinar Apr 25 on the fate of the US Survey foot
jalbrz replied 4 years, 11 months ago 39 Members · 112 Replies
We could just look to our neighbor that did the change….Few their think it was too difficult.
Converting coordinates from meters to US survey feet vs the international foot can lead up to a foot and a half discrepancy.
Saw it happen first hand with a county plan done in meters. Someone decided to multiply the coords by 3.2808 instead of 3700/1200.
Needless to say, he was wondering why the mons were coming up 1.5 feet out
Depends where you are in the zone. It can be much more in a big state.
.1 meter = 3937/1200 US Survey Feet
They should make it clearer that they are expecting meters, but for the vast majority of their customers that assumption will be correct.
That is a fact that was never taught in school. It was always 1 inch equal 2.54 centimeters.
I am amazed at how many drawings and other recorded information and abstractors that have varas being converted into feet by multiplying varas by either 2.77 or 2.78 and sometimes 3.
The real method is dividing varas by 0.39 to get feet.
1 international foot = 0.3048 meters which is 2.54cm to the inch.
The unit conversion feature in an HP50g or a TI89 from feet to meters is international feet to meters. 1,000,000 feet converts to 304,800 meters. Something to be aware of.
My calculator app has both (1,000,000 meters)…
For those such as myself that missed the Thursday webinar, it is now available. Enjoy.
Fate of the U.S. Survey Foot after 2022: A Conversation with NGS
Oh, good. Thank you for letting us know! I had to miss it due to a previously scheduled meeting.
I’m just one of those evil GIS people. Bwah-hah-hah! Seriously, I do coordinate systems and transformations at Esri.Here is the slide I was posting about…
The conversion to meters at the 1chain level is identical at 4 places as given so he seems to be assuming 1 chain = 66 ift so the usft varies a bit.
And I missed it because of a dental appointment….I didn’t mind going! ????
Here is somethuing I found. The BLM chain length is based on the U.S. Survey Foot by law. Several years ago I ran across the BLM definition of a meter, set by law, for the relationship to a chain, but can’t remember where I saw the article. As it stands now there is more than one definition of a meter being used and you can’t use the SI for the older work done in meters. Meters is a bunch of BS anyway.
When ??Gunter’s chain? is used without qualification, and always in the United States, the unit is (17th century ?? present), = 1?10 furlong = 4 perches= 22 yards = 66 feet = 20.1168 meters. In the United States these units are based upon the survey foot, not the international foot. A square chain = 4,356 square feet (approximately 404.686 square meters). One link = 7.92 inches, a hundredth of a chain.
The square link is a unit of area, = 62.75 square inches (404.686 square centimeters).
I think that NGS and Surveyors should be using the Meter or/and stay with the US Survey Foot. International foot will create more mess that system used now due mentioned by others small difference US Survey FT v. International FT. If we can’t adopt more practical Metric System than we need to stick with US Survey Feet. Meter is already adopted in all surveying CAD, GIS, point cloud and least square adjustment software products so it is no cost to switch if needed. Also carpenters may use Decimeter = 1/10 of meters if they want smaller units for convenience. If we adopt now International Foot (“new” foot) then after 10 years we will have to adopt meter anyway, so double transition cost (double whammy). Maybe it is my bias opinion due to the fact I used meter 15 years ago in Europe.
Well, I’ll be. So does the HP 50g. If you hit the scroll key twice from the units menu, there it is.
I don’t see it in the TI 89 menu, though.
Meters is a bunch of BS anyway.
Ha, square peg-round hole. Shoving meters over our existing cadastre,,,,,,,,,,,,, it can be done of course.
Sometime in the early 2000’s I was at the offices of a local engineering company looking at petition filing. One of the senior engineers slapped a plan set for the new road that kinda connected our two offices, he asked if I knew why it was important, “The last metric DOT job!!!!”. He was so happy to be done with it.
I don’t wish to speak for everyone, but that seemed to be the universal response.
What happened was the Superintendent of C&GS and Weights and Measures adopted the meter in the 1890s as the basic unit of measure then declared 1 foot equals 1200/3937 meters or 39.37 inches equals 1 meter. Tables were published to 4 places so rounded 1 chain equals 20.1168 meters which happens to be the same for international feet (but not rounded).
The problem arose in the early twentieth century when NIST or their predecessor at the request of other professions or industries changed the definition of the foot so that there would be no rounding in the conversion (1 foot equals 0.3048 meters exactly) and we’ve been dealing with it ever since. It didn’t happen instantly, it wasn’t until 1959 that it was changed everywhere then they kept the old definition too.
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