Imperial Japanese Geodetic Survey, Mapmaking,Maps: In context to Ph. T. Hunting

[Ben Valmores]

oh, i was so engrossed- did not noticed its now quarter to 5 in the morning...
I slept and woke up early though... i'll be back later folks to finish this thread.

Anyways, i'm nearing completion for all the supposed topics..and watch out for---

GAIHOZU

[Ben Valmores]

About Area Computations on pictures 116, 113,& 114;

One of the primary objects of most land surveys is to determine the area of tract of land is taken into projection upon a horizontal plane, and is not the actual area of the surface of the land. For precise determinations of the area of a large tract, such as a province or a country, the area is taken as a projection of the tract upon the earth's spheroidal surface at mean sea level.

There are actually 6 methods of determining areas:

1. Area of triangles
2. Area by coordinates
3. Area by coordinate squares
4. Area by double meridian distance or double parallel distance
5. Area of offsets from straight lines
 a) Trapezoidal rule
 b) Simpson's one third rule
6. Area by polar planimeter
________________________________

Area by triangles: The area of any field or tract can be found by dividing it up into a series of triangles, making the necessary measurements and then calculating the area by any of the usual trigonometric formulas. This method is excellent for small areas with few sides.

[Ben Valmores]

Partition of Land

There are many different problems which may arise in the subdivision of land and which may be solved simply by the application of the principles of trigonometry.

A subdivision often has the purpose of dividing an area into smaller parcels of a definite size.

Division of an area into certain proportional parts may be carried out by the use of special techniques in computations which involve the determination of missing bearings and distances of lines in a traverse.

Case 1: Dividing a tract of land into two parts by a line between two points
Case 2: Dividing a tract of land by a line running in a given direction
Case 3: To cut off a required area by a line through a given point
Case 4: To cut off a required area by a line running in a given directions

Measurements of Angles and Directions

The location of points and the orientation of lines frequently depend upon the measurement of angles and directions. In surveying, directions are given by bearings and azimuths.
We should know the basic principles of measuring and reckoning angles and directions.
We should learn how the relative direction of lines be obtained.

 Topics to learn:

1. Meridians:
a. True Meridian b. Magnetic Meridian c. Imaginary Meridian d. Grid Meridian

2. Methods of Determining or Establishing Meridians

a. Establishing Magnetic Meridian by Compass
b. Determining True North by aid of Sun and a Plumb line
c. Determining true north by the Rising and Setting of the Sun

3. Master the Units of Angular Measurement:

a. The Degree b. The Grad c. The Mil d. The Radian

4. Magnetic declination

5. Local Atrraction---( I have a true experiential story of one of our Survey Aides--he actually    found a small cache of treasure)

Measurements of Difference of Elevation: A very lenghty topic

Note:

In the context of Treasure Hunting, knowing various basic techniques & methods of getting exact distances, partitioning an area, mastery in getting the exact measurements of angles and directions increases our chances of success.
Subdivision of areas into smaller parcels, results in making maps that is of small scales.
This small scaled maps is what we should be wary about in Treasure Hunting.

Knowing the Measurements of exact Angles and Directions as much as Measurements of Difference of Elevation will lead us to the exact location of treasure.

All the points, grids and supposed monuments locations will be pointed out.
But all the important points will not be marked in the form of the usual survey monuments but by odd looking permanent structures, markers with signs.

[Ben Valmores]

Measurements of Angles and Directions

The location of points and the orientation of lines frequently depend upon the measurement of angles and directions. In surveying, directions are given by bearings and azimuths.
We should know the basic principles of measuring and reckoning angles and directions.
We should learn how the relative direction of lines be obtained.

 Topics to learn:

1. Meridians:
a. True Meridian b. Magnetic Meridian c. Imaginary Meridian d. Grid Meridian

2. Methods of Determining or Establishing Meridians

a. Establishing Magnetic Meridian by Compass
b. Determining True North by aid of Sun and a Plumb line
c. Determining true north by the Rising and Setting of the Sun
_____________________________________________________________

A meridian (or line of longitude):

 is the half of an imaginary great circle on the Earth's surface terminated by the North Pole and the South Pole, connecting points of equal longitude. The position of a point along the meridian is given by its latitude. Each meridian is perpendicular to all circles of latitude. Each is also the same size, being half of a great circle on the Earth's surface and therefore measuring 20,003.93 km (12,429.9 miles).
Meridian
 is a fixed line of reference for determining direction of lines.

1 . True Meridian

A north –south line passing through the geographical. It is sometimes known as the astronomic or geographic meridian and is generally adopted reference line.

2 . Magnetic Meridian

Lies parallel with the magnetic lines of force of the earth and is indicated by the direction of the magnetic needle of a compass.

3. Imaginary or Assumed Meridian

A reference line arbitrarily chosen or conceived and its relation to the true meridian ascertained later.

4. Grid Meridian

 A reference line based upon a plane coordinate system where grid north is parallel to a selected central meridian.

The angle between the magnetic and the true meridian is the magnetic declination, which is relevant for navigating with a compass.

Methods of Determining or Establishing Meridians

a. Establishing magnetic Meridian by Compass

The magnetic meridian can be established by setting the compass over any convenient point and then sighting to set a point or stake or other object that marks another point on the meridian. Several sights should be taken during the set-up. After each setting of the line of sight, the compass should be rotated about the vertical axis and then moved back until the needle reads zero. The mean of the point thus establish is assumed to be on the magnetic meridian, provided the observations are taken at a time of day when the declination is approximately at its mean value.

[Ben Valmores]

b.Determining true North by Aid of the Sun and a Plumb Line

On a level piece of ground, lean a pole toward the north and rest it in a crotch made by two sticks. Suspend a weight from the end of the pole so that it nearly touches the ground; then about an hour before noon, attach a string to a peg driven directly under the weight and, with sharpened stick attached to the other end of the string, describe an arc with a radius equal to the distance from the peg to the shadow of the tip of the pole. Drive a peg on the arc where the shadow of the tip of the pole rests.

 About an hour after noon, watch the shadow of the tip as it approaches the eastern side of the arc and drive another peg where it crosses. By means of a tape or a string, find the middle point of the straight line joining the last two pegs mentioned. A straight line joining this middle point and the peg under the weight will be True North.

[Ben Valmores]

c.   Determining True north by the Rising and Setting of the Sun

Observe the magnetic *azimuth of the sun at rising and setting on the same day or at setting on one day and rising the next. Add the two azimuths together.

Take the difference between this some and 360 degrees. One half of this difference is the declination of the compass and is East, if the sum of the two azimuths is less than 360 degrees; West, if it is greater.

In using this method the observations are best taken when the object is just above the true horizon.

(*Azimuth- is another term used to indicate the direction of lines. The azimuth of any line is the clockwise angle designated as beieng measured between either  the north end or the south end of the reference meridian and the line in question.)

Ex. The observed magnetic azimuth from north of the rising sun is just above the true horizon 110 degrees. As it is just about to set in the afternoon in the opposite horizon the observed azimuth from north is 260 degrees. Determine the magnetic declination.

[Ben Valmores]

Other alternate ways to Find True North Without a Compass

Which way is north? Whether you're lost in the woods or you're trying to install a sundial in your yard, you're bound to want to find true north from time to time, and chances are when the time comes you won't have a compass. What's more, even if you do have a compass, it will point to magnetic north, which, depending on your location in the world, can vary a great deal from true north. So what's an intrepid explorer to do?

Read this to find several different ways to find your way.


The Shadow-Tip Method (same logic to the sun and plumb line)

1. Place a stick upright in the ground so that you can see its shadow. Alternatively, you can use the shadow of a fixed object. Nearly any object will work, but the taller the object is, the easier it will be to see the movement of its shadow, and the narrower the tip of the object is, the more accurate the reading will be. Make sure the shadow is cast on a level, brush-free spot.

2. Mark the tip of the shadow with a small object, such as a pebble, or a distinct scratch in the ground. Try to make the mark as small as possible so as to pinpoint the shadow's tip, but make sure you can identify the mark later.

3. Wait 10-15 minutes. The shadow tip will move mostly from west to east in a curved line.

4. Mark the new position of the shadow's tip with another small object or scratch. It will likely move only a short distance.

5.Draw a straight line in the ground between the two marks. This is an approximate east-west line.

6.Stand with the first mark (west) on your left, and the other (east) on your right.You are now facing mostly toward true north, regardless of where you are in the world. The illustration shows that the sun and marker at Points 1 is what is happening for Step 2. At Points 2, it shows what is happening for Step 4. This method is based on the fact that the sun moves across the sky from East to West.

[Ben Valmores]

Alternate Shadow-Tip Method for Increased Accuracy

1. Set up a stick as perpendicular to the level ground as possible and mark the first shadow-tip as above. For this method, take your first reading in the morning, at least an hour or so before midday.

2. Find an object or length of string, etc., exactly the same length as the shadow.
 
3. Continue taking measurements of the shadow's length every 10-20 minutes. The shadow will shrink before midday and will grow after midday.

4. Measure the shadow length as the shadow grows. Use the string or object you used to measure the length of the initial shadow. When the shadow grows to exactly the same length as the string (and hence exactly the same length as your first measurement), mark the spot.

5. Draw a line connecting the first and second marks as above. Once again, this is your east-west line, and if you stand with the first mark on your left and the second on your right, you will be facing true north.


 

[Ben Valmores]

Using the Stars: Northern Hemisphere

1. Locate the North Star (Polaris) in the night sky. The North Star is the last star in the handle of the Little Dipper constellation. If you have trouble finding it, find the Big Dipper.

The two lowest stars in the Big Dipper (the outermost stars of the cup of the dipper) form a straight line that "points" to the North Star. You may also find the constellation Cassiopeia, which is always opposite the Big Dipper.

 The North Star is located about midway between the central star of Cassiopeia and the Big Dipper (see attached figure).

2. Draw an imaginary line straight down from the North Star to the ground. This direction is true north, and if you can find a landmark in the distance at this point, you can use it to guide yourself.

[Ben Valmores]

Using the Stars: Southern Hemisphere

1. Find the Southern Cross constellation. In the southern hemisphere, the North Star is not visible, and no single star always indicates north or south, but you can use the Southern Cross and the pointer stars as your guide.

 The Southern Cross constellation is formed by five stars, and the four brightest stars form a cross that is angled to one side.
 
2. Identify the two stars that make up the long axis of the cross. These stars form a line which "points" to an imaginary point in the sky which is above the South Pole. Follow the imaginary line down from the two stars five times the distance between them.

3. Draw an imaginary line from this point to the ground, and try to identify a corresponding landmark to steer by. Since this is true south, true north is directly opposite it (behind you as you are looking at the point).

[Ben Valmores]

Using the Stars: Southern Hemisphere

1. Find the Southern Cross constellation. In the southern hemisphere, the North Star is not visible, and no single star always indicates north or south, but you can use the Southern Cross and the pointer stars as your guide.

The Southern Cross constellation is formed by five stars, and the four brightest stars form a cross that is angled to one side.
 
2. Identify the two stars that make up the long axis of the cross. These stars form a line which "points" to an imaginary point in the sky which is above the South Pole. Follow the imaginary line down from the two stars five times the distance between them.

3.Draw an imaginary line from this point to the ground, and try to identify a corresponding landmark to steer by. Since this is true south, true north is directly opposite it (behind you as you are looking at the point).

[Ben Valmores]

Using the Stars: Equator

1. The Orion Constellation is visible from both hemispheres depending on the time of the year. It is a permanent feature on the equator.

2.Look for Orion's Belt. Orion has several prominent stars. The 'belt' (3 stars in a row) runs from East to West. Look for that, it has a 'sword' attached to it.

3. Look in the direction opposite where the belt was. You should be able to make out its 'head' and arms. That is the general direction of North.

4. Orion lays across teh Equator:teh Belt rises & sets at east & West

[Ben Valmores]

Watch Method: Northern Hemisphere

1. Find an analog watch (the kind with hour and minute hands) that is set accurately.Place it on a level surface, such as the ground, or hold it horizontal in your hand.

2. Point the hour hand at the sun.
 
3. Bisect (that is, find the centre point of) the angle between the hour hand and the twelve o'clock mark (the number 12 on the watch). The centre of the angle between the hour hand and twelve o'clock mark is the north-south line.

If you don't know which way is north and which south, just remember that no matter where you are, the sun rises in the east and sets in the west.
ask a mason...

In the northern hemisphere the sun is due south at midday. If your watch is set to daylight saving time bisect the angle between the hour hand and the one o'clock mark instead.

Watch Method: Southern Hemisphere

1. Use an analogue watch as above, and point the watch's twelve o'clock mark (the number 12) toward the sun. If your watch is set to daylight saving time, point the one o'clock mark toward the sun.

2. Bisect the angle between the twelve o'clock mark (or one o'clock mark if using daylight saving time) and the hour hand to find the north-south line. If you're unsure which way is north, remember that the sun rises in the east and sets in the west no matter where you are. In the southern hemisphere, however, the sun is due north at midday.

Tips

• When trying to locate the North Star it is important to remember that, despite popular belief, the North Star is NOT the brightest star in the sky. The only remarkable thing about it is that it is the only star in the sky that does not move.

• If you only have a digital watch, you can still aim the watch accurately at the sun, as you figure out where the hour hand will be. Use 12, 3, 6 and 9 o clock's angles to guide you to the other hours, smaller increments for half/quarter hours.

• In Northern Hemisphere, halfway between hour hand and 12 is South. Halfway between 12 and hour hand in Southern Hemisphere is North.

• These methods may require practice to perfect, so it's a good idea to try them a couple times when you can check your readings. That way, you'll be able to rely on them if you're in a survival situation.

• If you have a 24h dial on your clock (like many pilot watches), then just point the hour hand at the sun, and north is at the 0/24h mark

Warnings

• The North Star becomes higher in the sky the further north you travel, and it is not useful about 70° N latitude.

• The shadow-tip methods are not recommended in the polar regions, which are latitudes above 60° in either hemisphere.

• The watch method is not recommended in lower latitudes, particularly below 20° in either hemisphere.

[Ben Valmores]

  :-[uh uhh redundant pic sorry...it should have been the watch pic.

Anyways here's more pics for you to associate your understandings with its related readings

[Ben Valmores]

Note: Use of a compass

This can work but will be inaccurate because the compass points at magnetic north and you must correct for magnetic deviation.

Magnetic deviation varies around the world and even changes over time. It can even be affected  by local forces such as the presence of steel and magnetic rocks.
(LOCAL ATRRACTION). This is not a recommended method.

These other methods (without using a magnetic compass) of deriving true north and south is extremely accurate and is favorable over magnetic compasses in situations where magnetic fields may interfere with your results.

Whats the difference between "true north" and "magnetic north"?

True North is land-based while Magnetic North isn't. This makes True North constant and stable while the Magnetic North is flexible. You can determine the location of True North by the North Star while you cannot with Magnetic North; it is generally determined by simply pointing the needle of the compass.
 
True north is a constant and refers to the geographic North Pole. Magnetic north tends to shift and refers to the pole of the Earth's magnetic field. In mid 2002, true north and magnetic north were approximately 590 miles apart.

The poles of the Earth's magnetic field are different from its geographic poles. Maps are aligned along true north, so hunters have to make adjustments when navigating by compass.

In navigation, the difference between true north and magnetic north is known as declination. Almost all, Geological Survey maps print relevant declination information, and the maps are updated every five years to account for shift.

Those traveling in Northern California, for instance, have to make declination adjustments of roughly 18 degrees.
The Earth's magnetic field stems from its molten metallic core, much of which is iron. Iron is a fairly common element, since it can't be burned off during the fiery formation of stars. Iron is magnetic because its inner electron shells are slightly unstable.

Solution?

Some create a deviation card by doing a compass swing.
Traditionally this would be done by taking bearings on fixed land features, nowadays however GPS which is not subject to magnetic deviation can be used to compare headings.[/u]

The deviation card can then be used when converting between compass and magnetic headings.
There are a few, fortunately rare, locations in the earth's magnetic field where magnetic anomalies occur.
Fortunately these sources of magnetic anomaly will be indicated on your charts.

The CADET rule for variation;

When converting from Compass Add East to get True.
It follows that converting from true to magnetic is the reverse, subtract east.

For deviation you can use the saying;

Deviation east, compass least, in other words subtract from the magnetic course.
Deviation west compass best, in other words add the correction.


 
more next....