Why Mean Low Tide?

[MicHughV]

the state of the tide is one thing...but where....tide tables usually give tables for one location, and then add plus or minus times for other locations....if your location isn't noted, you have to take the closest location.....and do your own interpolation...

the tide tables also do not take into account things like water flow and direction..

rivers are particularly prone in confusing the mariner....low tide may be at...say 10 am....but the river flow doesn't stop until 11:45 ....in order words....low tide doesn't always coincide with a change on water velocity direction...

and then there is wind enhanced tides...which can swing any noted tidal range time and height out the door by a substantial amount...I've learned this the hard way....

not mention to mention shifting sand bars...

tide tables are simply a tool.....not a guide per se...the mariner should recognize that other "variables" should also be considered before getting acquainted with the bottom.

[Benz]

Originally Posted by jdmuys

You are right. All the scientists everywhere in the world, including in the USA are imbeciles for using the metric system everywhere. They claim it's simpler and avoids mistakes because you only use power of tens for scaling. As if multiplying by combinations of powers of 20, 12 or other numbers was more difficult. And NASA scientists and engineers are all imbecile for losing the $100 millions+ Mars Climate Orbiter because they tried using the metric system to compute its trajectories.

Sometimes, the arrogance and hubris of some people is surprising, from a country that didn't even have a continental map of their own country until over 20 years after the metric system was adopted.

If someone had simply not tried to use the metric system for the Mars orbiter, but had continued to use the system that put men on the moon and won WWII (not in that order), the mission would have probably succeeded. It was because there was a metric system, and because someone tried to use it where it didn't belong (in the actual getting of things done) that the orbiter failed.
But does it not seem arrogant for the "rest of the world" to insist that we should join them in their folly? I don't foam and rage at other countries for measuring things wrong--let them. The only reason our maintaining our time-honored system bothers them is because of their colossal insecurities. After all, which of them has put men on the moon?
But we've been down this road before on this forum, and I have little interest in exploring it again. Measure things how you will, and learn to adapt when you find a chart datum that doesn't suit your fancy. Or don't--and run aground. It's up to you.

[boatman61]

Originally Posted by MicHughV

the state of the tide is one thing...but where....tide tables usually give tables for one location, and then add plus or minus times for other locations....if your location isn't noted, you have to take the closest location.....and do your own interpolation...

the tide tables also do not take into account things like water flow and direction..

rivers are particularly prone in confusing the mariner....low tide may be at...say 10 am....but the river flow doesn't stop until 11:45 ....in order words....low tide doesn't always coincide with a change on water velocity direction...

and then there is wind enhanced tides...which can swing any noted tidal range time and height out the door by a substantial amount...I've learned this the hard way....



tide tables are simply a tool.....not a guide per se...the mariner should recognize that other "variables" should also be considered before getting acquainted with the bottom.

Tell me about it.. spent 5 days sitting at the jetty front of The Bean in Oriental and pissed off the Sheriff coz I was there for more than the allotted 48hrs..
A strong prolonged Westerly pushed the waters out of Pamlico Sound and had me sitting on the bottom.. embarrassing to say the least.

[requiem]

Originally Posted by Benz

After all, which of them has put men on the moon?

Well, ISTR von Braun and his team used metric when doing the design work.

[Adelie]

Originally Posted by Benz

If someone had simply not tried to use the metric system for the Mars orbiter, but had continued to use the system that put men on the moon and won WWII (not in that order), the mission would have probably succeeded. It was because there was a metric system, and because someone tried to use it where it didn't belong (in the actual getting of things done) that the orbiter failed.
But does it not seem arrogant for the "rest of the world" to insist that we should join them in their folly? I don't foam and rage at other countries for measuring things wrong--let them. The only reason our maintaining our time-honored system bothers them is because of their colossal insecurities. After all, which of them has put men on the moon?
But we've been down this road before on this forum, and I have little interest in exploring it again. Measure things how you will, and learn to adapt when you find a chart datum that doesn't suit your fancy. Or don't--and run aground. It's up to you.

No, I would say it was because Lockheed failed to follow the terms of their contract with NASA that required the use of Metric and and contrary to its own specification that indicated the results would be in SI, but instead they provided a piece of navigational equipment that provided results in English Customary units..

Likewise NASA is at fault for not checking Lockheed's work more thoroughly.

[zboss]

It's not a question of where he grips it! It's a simple question of weight ratios! A five ounce bird could not carry a one pound coconut.

[StuM]

Originally Posted by Benz

But does it not seem arrogant for the "rest of the world" to insist that we should join them in their folly? I

The rest of the world don't insist on you doing anything. It just tells you what we are using and what you need to use if you want to share technology with us.


If you chose to continue to use a cumbersome, archaic system internally instead of the logical, internationally accepted units (which your government agencies do use), that's fine by the rest of us. But don't expect us to work with your units. That's the arrogance.

[StuM]

Originally Posted by requiem

Well, ISTR von Braun and his team used metric when doing the design work.

And NASA followed the US legally required practice of using metric units.

https://www.nist.gov/system/files/do...tric/1136a.pdf
Congress passed the MetricConversion Act of 1975 “to coordinate and plan the increasing use of the metric system in the United States.”
...
Congress, recognizing the necessity of the United States’ conformance with international standards for trade, included new encouragement for U.S.industrial metrication in the Omnibus Trade and Competitiveness Act of 1988. This legislation amended the Metric Conversion Act of 1975 and designates the metric system as the preferred system of weights and measures for United States trade and commerce.” The legislation states that the Federal Government has a responsibility to assist industry, especially small business, as it voluntarily converts to the metric system of measurement. Federal agencies were required by this legislation,with certain exceptions, to use the metric system in their procurement, grants and other business-related activities by the end of 1992.

It was Lockheed's obstinate refusal to follow the recommendation when working with agencies known to be using it (indeed, required to use it) that caused the Mars disaster.

[StuM]

Originally Posted by zboss

It's not a question of where he grips it! It's a simple question of weight ratios! A five ounce bird could not carry a one pound coconut.

It could be carried by an African swallow... but they're not migratory

[jdmuys]

Originally Posted by Benz

If someone had simply not tried to use the metric system for the Mars orbiter, but had continued to use the system that put men on the moon and won WWII (not in that order), the mission would have probably succeeded.

Let me add one onto that. According to Don Eyles, the Apollo mission used the metric system, only to convert to imperial units for display purposes (thus adding to complexity).

It might be time for you to recognize you might have been wrong. I will not hold my breath.

[jdmuys]

Interestingly, according to NOAA:

All but a handful of NOAA’s 1,000-plus raster nautical charts show depths in feet or fathoms; however, IHO ENC product specifications state that all depths must be encoded in meters. When NOAA digitized paper charts in the 1990s to create the first NOAA ENCs, depth values for soundings, depth curves, and other features with depths were converted from fathoms or feet into meters to populate the ENC database.
As a result, soundings and depth areas in the current suite of NOAA ENCs are compiled in fathoms and feet, but stored and displayed in ECDIS in decimal metric values, as shown in Figure 4.
1 fm 2 fms 3 fms 5 fms
6 ft 12 ft 18 ft 30 ft
1.8 m 3.6 m 5.4 m 9.1 m
This presents mariners with a rather unwieldy set of depth contour values to decipher when viewed in an ECDIS.

This is taken from this: https://nauticalcharts.noaa.gov/publ...sformation.pdf

[SeanPatrick]

Originally Posted by StuM

[...] what you need to use if you want to share technology with us.

Well, thank you for the privilege. If history is any indicator, I think you'll take our technology no matter how it's measured.

[Benz]

Originally Posted by StuM

And NASA followed the US legally required practice of using metric units.

https://www.nist.gov/system/files/do...tric/1136a.pdf
Congress passed the MetricConversion Act of 1975 “to coordinate and plan the increasing use of the metric system in the United States.”
...
Congress, recognizing the necessity of the United States’ conformance with international standards for trade, included new encouragement for U.S.industrial metrication in the Omnibus Trade and Competitiveness Act of 1988. This legislation amended the Metric Conversion Act of 1975 and designates the metric system as the preferred system of weights and measures for United States trade and commerce.” The legislation states that the Federal Government has a responsibility to assist industry, especially small business, as it voluntarily converts to the metric system of measurement. Federal agencies were required by this legislation,with certain exceptions, to use the metric system in their procurement, grants and other business-related activities by the end of 1992.

It was Lockheed's obstinate refusal to follow the recommendation when working with agencies known to be using it (indeed, required to use it) that caused the Mars disaster.

And again, if the US government, which makes A LOT of mistakes, had not made the mistake of passing that act, and NASA had continued to use the units that Lockheed had used to become a technological giant, the orbiter would have been a smashing success.
But notice the language of "voluntarily converts." It is clear, 40+ years after, that we will not voluntarily convert. It's time to give up on metric, or SI, or whatever it's called now, with all its different notations, and its ever-changing definition of the base unit of measurement (anyone know what it was changed to LAST YEAR?).
Interestingly enough, I have run across many pockets of the world where though metric is 'official,' people are navigating in fathoms and nautical miles, and measuring in feet. Newfoundland, Quebec (Quebec!), Nicaragua, Panama, plus EVERY SINGLE AIRLINE PILOT. Why? because it works. It works well. Why fix what ain't broke?

[StuM]

Originally Posted by Benz

... the orbiter would have been a smashing success.

It was - a huge smash hit!

[zboss]

I can't believe that we are still having arguments over the metric system in the US. Can we just adopt it once and for all? My gosh...

also... why bother with nautical measures at all like "knots". Just everyone switch to Kph!