I had to learn to do these in college in the 1980's, but never had to do one on the job.
We use to figure a lot of areas with double meridian distances. I probably haven't even uttered the phrase since the HP41 came on the scene.
I use to 'bust' boundaries up into triangles for area calcs and then take the sum of all the pieces for the total area. It's a lot easier than dmds while sitting in a truck.
I've been studying the Surveyors reference manual recently saw the DMD section and had wondered if anyone actually uses these. Might be a topic I just need to know and store in the back of my head until Test time.
The above sheet is dated about a month before I started surveying (9/27/1968).
Filled my share of those in back in the late 60s & early 70s (don't miss them one bit).
B-)
Not only remember them, but teach them in one of my workshops. But also teach "cross multiplying coordinates" which is much easier.
Had to know them (and use them) back in the olden days when I took the exam.
In 1981 I had to close a 15 leg traverse by DMD without the benefit of a calculator for the TN PLS exam, that's the last time I did that! I've even forgotten how to determine a square root long hand!
Dtp
Yep! Used them a lot! Because there was no such thing as a calculator that would produce sine, cosine etc, back then (1970 - 1072 ± ) we were forced to look those up in a book!! Oh, talk about the chance of transposition errors! For sure!. I might have that book around yet! We thought we had it made when Casio came out with the FX-1! Sine and cosine at the touch of a button! For what it was - at the time - it was great!! Great enough to justify the like $700 price tag!
> I had to learn to do these in college in the 1980's, but never had to do one on the job.
Still teaching it in elementary surveying today.
Steve
Remember them well. Col. Epps taught us in survey school in late 1963. Understanding DMDs is an excellent base for learning technical surveying.
Sure, and had my students do them before area by coordinates. I always thought it helped the learning process to see how things could be worked out long hand, long thought. But they tell me I'm wrong so I gave it up.
I remember being shown how to do them in the early 60s. I liked to skip lines and create a separate column called "Meridian Distance" for each point. That made it easier to keep track of what numbers to add when figuring the double meridian distances.
In the late 60s, when the first digital desktop calculators started coming in, I recall using a similar method to calculate cross-section areas. Trig functions weren't needed for that. The elevations at each end of a line were added to give the equivalent of a DMD and the horizontal distances took the place of the departures. It wasn't any faster than using a planimeter, but it was more accurate.
Who remembers these? DMD's and 16 figure logs
The way it was, along with 16 figure logs. No calculators as we know them in my early exams.
The Facit was very quick at knocking those figures into shape though.
Then came HP and bliss!! But not for the chainman. I'd have the next peg calculated before he walked back after rolling up the chain.:-(
DMD, Calcul sheets, Trig Tables which had to be interpolated is how I started. Then the HP35 came out. It was worth the $400 in early 70's money. Then when the HP45 came out with the Summation and minutes and seconds to decimal of degree keys that was worth another $400. However, I for one would not want to go back.
yep,I remember.
I remember, still have some of the 'blank sheets" in the file cabinet, some where.
> I had to learn to do these in college in the 1980's, but never had to do one on the job.
>
>
I've done a ton of those. I miss it sometimes, believe it or not.
Pre-cad and pre-calculators
Those were the days!
I remember doing volume calculations for dam fill by hand. Different lengths of sections. Different top widths. Different heights along the dam. Different front and back slopes. Good way to kill a full day or more. Always hoping you were getting each separate calculation correct.
Then someone steps into your office and says, "When you have that done, change the back slope to such and such so we can see how much that would change things."
> I had to learn to do these in college in the 1980's, but never had to do one on the job.
>
I learned this in college ( Univ.of AR) in the early 80's also. Compass Rule, Transit rule, Area by Coordinates progressed from DMD
Used an 11c and 'mashed' the P>R (R>P) endlessly.
Also used the ? key to mash out area by coordinates
DMD the method I used most until about 1974.
Dividing a property into triangles was also a good method.
Then I started working at a company that had an Olivetti mechanical calculator about the size of a desktop computer that sat on a thick foam pad and would jump violently every time the carriage returned. It used data cards that had to be loaded every morning and between different routines.
The DMD method has often been considered the legal and required method in Texas by some.
Used that method and made my own DMD sheets when I took State Exam.
In the early 80s I prepared a DMD routine using program called D Base 3. Then I discovered Carlson Surveyor 1.
Still have DMD sheets archived in my files. Remember using them, but could not for the life of me explain step by step how to do it any more. It is easier to type for me now than to write by hand.
B-)
