Discussion Map makers and topographic engineers.

19thGeorgia

1st Lieutenant
Joined
Apr 4, 2017
Gotta hand it to you, creating a gratuitous put down for Merrill's maps is quite an accomplishment. Union cavalry was ordered to concentrate at Rover. Try finding Rover on Gen. Polk's map. That is what these examples are about, not how neat they were... which they are in both the original & modern meaning of the word.
Hey, I've got a lot more detail on these homespun/homemade Confederate maps than the fancy Yankee maps.

Union
From LOC description: Signed in ink on verso: "W.T. Sherman, Maj. Gen. Map used by General Sherman in the campaign of 1864."
buckheadyankee.jpg


Confederate
LOC description: Labeled "For Maj. Gen. French from Engineers Office Army of Miss. Walter J. Morris Chief Engineer." Shows roads, creeks, and names of residents.
buckheadrebel.jpg
 

Rhea Cole

1st Lieutenant
Joined
Nov 2, 2019
Location
Murfreesboro, Tennessee
Hey, I've got a lot more detail on these homespun/homemade Confederate maps than the fancy Yankee maps.

Union
From LOC description: Signed in ink on verso: "W.T. Sherman, Maj. Gen. Map used by General Sherman in the campaign of 1864."
View attachment 403893

Confederate
LOC description: Labeled "For Maj. Gen. French from Engineers Office Army of Miss. Walter J. Morris Chief Engineer." Shows roads, creeks, and names of residents.
View attachment 403894
Gotta hand it to ya', it is a very blunt point, but is a point. Whatever you do, don't look up Merrill's maps in the official atlas... far too neat, far too accurate for your taste.
 
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Rhea Cole

1st Lieutenant
Joined
Nov 2, 2019
Location
Murfreesboro, Tennessee
I don't even understand how you can make a topographical (with elevations) map without aerial photography.
They used triangulation. Here is a simple way to do it. Stand across the street from a power pole or street light. Have an assistant stand next to the pole.

Hold a broom handle vertically at arms length. Aim at the base of the pole with the hand griping the stick & the tip of the handle with the top of the pole. Keeping your arm outstretched, rotate the handle parallel with the curb. Instruct your helper to step along the curb or sidewalk until you sight them along the tip of the handle.

You & your helper will be standing on the hypotenuse of a right triangle. The distance between your helper & the pole is the height of the pole. If you know the length of any one of the sides, you also know the length of the other two. Congrats, you are now a Roman engineer.

A right triangle is 3X4X5. The Egyptians used that fact to lay out their monumental constructions with exquisite accuracy. Military engineers used that simple triangulation technique for millennia. By the Civil War, surveying equipment was quite sophisticated & not dependent on right triangles.

This is the same principle that is used to find latitude. A triangle drawn with an imaginary line along the earth’s axis to the North Star & to your position tells you where you are in relation to the celestial North Pole. Standing on the pole, your sextant will be vertical, i. e. 90 degrees. Every step southward increases the angle proportionally.

West Point officers were trained to use theodolites & triangulation to chart very accurate mapping points. Connect the dots & you have a map. Triangulation in both vertical & horizontal orientation was & is the key to map making & navigation. It is what makes GPS possible.
 
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Lubliner

Captain
Forum Host
Joined
Nov 27, 2018
Location
Chattanooga, Tennessee
I worked for a brief stint in 1982 as an assistant in a company that copied blueprints. In that era 39 years ago it was a remarkably complex machine with an ammonia tank attachment, if I remember correctly. Blueprints were huge, and so the machine.
Lubliner.
 

infomanpa

2nd Lieutenant
Joined
Feb 18, 2017
Location
Pennsylvania
They used triangulation. Here is a simple way to do it. Stand across the street from a power pole or street light. Have an assistant stand next to the pole.

Hold a broom handle vertically at arms length. Aim at the base of the pole with the hand griping the stick & the tip of the handle with the top of the pole. Keeping your arm outstretched, rotate the handle parallel with the curb. Instruct your helper to step along the curb or sidewalk until you sight them along the tip of the handle.

You & your helper will be standing on the hypotenuse of a right triangle. The distance between your helper & the pole is the height of the pole. If you know the length of any one of the sides, you also know the length of the other two. Congrats, you are now a Roman engineer.

A right triangle is 3X4X5. The Egyptians used that fact to lay out their monumental constructions with exquisite accuracy. Military engineers used that simple triangulation technique for millennia. By the Civil War, surveying equipment was quite sophisticated & not dependent on right triangles.

This is the same principle that is used to find latitude. A triangle drawn with an imaginary line along the earth’s axis to the North Star & to your position tells you where you are in relation to the celestial North Pole. Standing on the pole, your sextant will be vertical, i. e. 90 degrees. Every step southward increases the angle proportionally.

West Point officers were trained to use theodolites & triangulation to chart very accurate mapping points. Connect the dots & you have a map. Triangulation in both vertical & horizontal orientation was & is the key to map making & navigation. It is what makes GPS possible.
Thanks. I knew about triangulation for 2D, but didn't think about the 3D aspect. I should have known this because I developed a formula for determining whether an elevation will obstruct your line of sight to a more distant object.
 

Rhea Cole

1st Lieutenant
Joined
Nov 2, 2019
Location
Murfreesboro, Tennessee
Not exactly. I just like to use a topographical map to determine visibility from point to point without actually having to be there.
You would enjoy looking at the position of CW signal stations. On very cold still nights, the Fort Transit station on Pilot Knob east of Murfreesboro TN could signal directly to Fort Negley station on downtown Nashville. They used turpentine torches at night. It is a distance of 41 miles. They had large naval telescopes.

Fort Transit station was 60 feet up in an enormous tree. Fort Negley station was a treehouse platform in a tree on the west side of the fort. Can’t beat Pilot Knob for sight lines. It is the tallest point between there & some place in New Mexico. It is a 360 degree vista.
 

John Winn

Major
Joined
Mar 13, 2014
Location
State of Jefferson
Thanks. I knew about triangulation for 2D, but didn't think about the 3D aspect. I should have known this because I developed a formula for determining whether an elevation will obstruct your line of sight to a more distant object.
That's cool that you worked that out. When I was working as a GIS specialist I used to do that all the time as my agency often needed to determine if a timber cut or a road would be visible from various places (e.g. from the Interstate or a park). Of course, I had software.

As @Rhea Cole noted one can construct a sort of topo map with a few relatively simple tools. However, while you can draw the terrain, without an altimeter you really can't construct a true topo (i.e. with elevation lines), at least not in a day or two.
 

Rhea Cole

1st Lieutenant
Joined
Nov 2, 2019
Location
Murfreesboro, Tennessee
That's cool that you worked that out. When I was working as a GIS specialist I used to do that all the time as my agency often needed to determine if a timber cut or a road would be visible from various places (e.g. from the Interstate or a park). Of course, I had software.

As @Rhea Cole noted one can construct a sort of topo map with a few relatively simple tools. However, while you can draw the terrain, without an altimeter you really can't construct a true topo (i.e. with elevation lines), at least not in a day or two.
Actually, it isn’t difficult to to establish grades with triangulation. From two vantage points fix a position as your baseline. From there, the subsequent points are sighted with both vertical & horizontal angles. Think of it as a staircase seen from the side for simplicity sake.

From a spot on the floor traverse until you sight where the bottom step lands. Raise your sight the equivalent of 7” vertically. Move until you line up with the kicker of the next step, write down the horizontal angle from your reference point. Do that until you reach the landing. The horizontal angle will be four times as wide as the steps are. You will have created a set of reference points that accurately depict the rise & run of the stairway. Match the results with those of another vantage point & you will be able to place your dots in relation to the room. Do the same for the other side of the steps, connect the dots & you have your topo lines.

It is a simple process, but doing the math w/o a calculator will take you a while. When my college age self was introduced to the first Texas Instrument hand held calculator it was like wrapping my fists around the Holy Grail.
 
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John Winn

Major
Joined
Mar 13, 2014
Location
State of Jefferson
Actually, it isn’t difficult to to establish grades with triangulation. From two vantage points fix a position as your baseline. From there, the subsequent points are sighted with both vertical & horizontal angles. Think of it as a staircase seen from the side for simplicity sake.

From a spot on the floor traverse until you sight where the bottom step lands. Raise your sight the equivalent of 7” vertically. Move until you line up with the kicker of the next step, write down the horizontal angle from your reference point. Do that until you reach the landing. The horizontal angle will me four times as wide as the steps are. You will have created a set of reference points that accurately depict the rise & run of the stairway. Match the results with those of another vantage point & you will be able to place your dots in relation to the room. Do the same for the other side of the steps, connect the dots & you have your topo lines.

It is a simple process, but doing the math w/o a calculator will take you a while. When my college age self was introduced to the first Texas Instrument hand held calculator it was like wrapping my hands around the Holy Grail.
Yeah, you can establish grades - which is to say one can draw the terrain - but you won't have actual elevations. That's what I was saying earlier. I, too, remember the first Texas Instrument calculators. The ones with a square root key were hot. For a while some profs wouldn't allow them in class. And they were big. I bought one and had it for years. Eventually, though, it just became obsolete and way too big and clumsy. My wife still has her dad's 1940s slide rule but I've long forgotten how to use one of those (yea, I had to learn in my first college math class).
 

Rhea Cole

1st Lieutenant
Joined
Nov 2, 2019
Location
Murfreesboro, Tennessee
Yeah, you can establish grades - which is to say one can draw the terrain - but you won't have actual elevations. That's what I was saying earlier. I, too, remember the first Texas Instrument calculators. The ones with a square root key were hot. For a while some profs wouldn't allow them in class. And they were big. I bought one and had it for years. Eventually, though, it just became obsolete and way too big and clumsy. My wife still has her dad's 1940s slide rule but I've long forgotten how to use one of those (yea, I had to learn in my first college math class).
If you know the elevation of your starting point, you know the height of your other points in relation to it. You only have to know one point’s altitude, longitude & latitude to establish all the others. That is what all those Geological Study reference points are all about. I see one regularly on my walks about town here in Murfreesboro.

My Boy Scout leader had been a Marine artillery spotter in WWII & was a fanatical map reading instructor. We measured the heights of the spire on the courthouse & the height of the windows in relation to the Geological Survey point in the lawn. Even a group of befuddled 10 year olds can do that.

Another method is to set a vertical stick into the ground. Attach a string to another stick & scrape a circle. With a helper, sight along your string to establish horizontal & vertical angles using a plumb bob protractor. People have been at this a very long time. Have you ever seen the aqueducts that stretch from horizon to horizon in Spain? They had to follow a very exact grade.
 

John Winn

Major
Joined
Mar 13, 2014
Location
State of Jefferson
If you know the elevation of your starting point, you know the height of your other points in relation to it. You only have to know one point’s altitude, longitude & latitude to establish all the others. That is what all those Geological Study reference points are all about. I see one regularly on my walks about town here in Murfreesboro.

My Boy Scout leader had been a Marine artillery spotter in WWII & was a fanatical map reading instructor. We measured the heights of the spire on the courthouse & the height of the windows in relation to the Geological Survey point in the lawn. Even a group of befuddled 10 year olds can do that.

Another method is to set a vertical stick into the ground. Attach a string to another stick & scrape a circle. With a helper, sight along your string to establish horizontal & vertical angles using a plumb bob protractor. People have been at this a very long time. Have you ever seen the aqueducts that stretch from horizon to horizon in Spain? They had to follow a very exact grade.
I understand. My point was that someone out in the field trying to produce a topo map in a hurry isn't going to be successful. As you note, one definitely would need a known elevation starting point and I doubt those were commonly established in the mid-nineteenth century (unlike now where there are markers in many places). One can certainly calculate grade but that's just change over distance; i.e. not actual elevation above sea level.

We needn't quibble. I understand 'the ancients' could do a lot with relatively simple tools and calculations. I definitely admire those early map makers because I know what it took to do it in their day.
 

Rhea Cole

1st Lieutenant
Joined
Nov 2, 2019
Location
Murfreesboro, Tennessee
I understand. My point was that someone out in the field trying to produce a topo map in a hurry isn't going to be successful. As you note, one definitely would need a known elevation starting point and I doubt those were commonly established in the mid-nineteenth century (unlike now where there are markers in many places). One can certainly calculate grade but that's just change over distance; i.e. not actual elevation above sea level.

We needn't quibble. I understand 'the ancients' could do a lot with relatively simple tools and calculations. I definitely admire those early map makers because I know what it took to do it in their day.
During the 150th at Chattanooga, we signaled to point park with original visual sigs at the time they were transmitted. At the park was a engineer reenactment group. They were pros who had period surveying instruments. Unfortunately, I was busy waving flags & didn’t get to talk with them like I would have.
 

Rhea Cole

1st Lieutenant
Joined
Nov 2, 2019
Location
Murfreesboro, Tennessee
In the 18th & 19th Centuries the formula ( h = x tang. a ) is how to use a sextant or inclinometer to measure altitude. The altitude was measured in relation to a point of know height above sea level at noon. It was the angle to the sun at noon relative to the point in question that was the key to establishing altitude. That is why I referred to the USGS benchmark discs such as the one near my house.

IMG_1428.jpg

Drawing of Mount Chimborazo
This is the view I had from my front door in 1976, Ambato, Ecuador.
In those heroic days, Explorers like Baron Von Humbolt ( one of my personal favorites. ) used triangulation beginning at the Pacific Ocean waterline on the coast of Ecuador to establish Mount Chimborazo as the tallest mountain in the world… that had been measured at that time as it turned out. Due to the equatorial bulge, Chimborazo is the furthest point away from the center of the earth.

The lines showing relative height in CW era maps can be nothing more than educated guesses. However, little + marks with altitude above sea level marked on CW era maps are the result of much sweat & pages of calculations. Just because it was laborious does not mean it wasn’t accurate.
 
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Rhea Cole

1st Lieutenant
Joined
Nov 2, 2019
Location
Murfreesboro, Tennessee
IMG_1372 2.jpg

Lookout Mountain from the porch at Sugar's BBQ on Missionary Ridge.
How would you make a map of what you are seeing?​

IMG_1530.jpg



In answer to a private message, "How did they do it?"
The answer was a Civil War GPS in the palm of their hand.



IMG_1523.jpg

This modern sighting compass is identical to the ones carried by Civil War soldiers.
Note the flat spots at 3:00 & 9:00 on the case. They allow it to be set on a level surface.

IMG_1531.jpg


Notice that the compass is designed to be read in the mirror.
You aim at a point & use the lever visible in the 2:00 position to lock the compass needle in place.
It make it easy to write down the result.

IMG_1526.jpg


This is the inclinometer. Note the E on the compass is boxed by the needle indicating 0 degrees.

IMG_1527.jpg


Compare the position of the E on the compass face with the position of the pointer in this image.
Notice that the degrees are meant to be read in the mirror.
What this allows you to do is to sight your point & call out the results to a helper who writes them down.

This handy-dandy compass/inclinometer was an essential piece of personal equipment for engineers & artillery officers.

Fortress Rosecrans.jpeg

Fortress Rosecrans outside Murfreesboro TN
The lines with ranges in yards were made using survey instruments.
The intersections of the lines were marked by white poles with little flags on them.
In December 1864 the Washington Artillery went into battery over a mile from Lunette Negley & Battery cruft.
The first round fired by the 20 pound Parrotts struck a caisson.
A rain of accurate fire drove off the CSA artillery before they could fire a shot.
About ten years ago, a cluster of Parrott shells was discovered at that site.
The rain soaked soil had absorbed the impact of the contact fused rounds without setting them off.
An O.E.D. unit from Fort Campbell blew them up in place.

 
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