Map Projections

Even though they are easy to fold up and carry around,
neither greatly distorted maps nor disassembled globe
gores have much practical use. For this reason,
cartographers have developed a number of map projections,
or methods for translating a sphere into a flat surface. No
projection is perfect - they all stretch, tear or compress the
features of the Earth to some degree. However, different
projections distort different qualities of the map. "All maps
have some degree of inaccuracy," Turner explains. "We're
taking a round Earth and projecting it onto a two-
dimensional surface -- onto a piece of paper or a computer
screen -- so there's going to be some distortion."
Fortunately, the variety of available projections makes it
possible for a cartographer to choose one that preserves
the accuracy of certain features while distorting less
important ones.
Creating a map projection is often a highly mathematical
process in which a computer uses algorithms to translate
points on a sphere to points on a plane. But you can think
of it as copying the features of a globe onto a curved
shape that you can cut open and lay flat -- a cylinder or a
cone. These shapes are tangent to, or touching, the Earth
at one point or along one line, or they are secant to the
Earth, cutting through it along one or more lines. You can
also project portions of the Earth directly onto a tangent or
secant plane.

Projections tend to be the most accurate along the point or
line at which they touch the planet. Each shape can touch
or cut through the Earth at any point and from any angle,
dramatically changing the area that is most accurate and
the shape of the finished map.
A planar projection
IMAGE COURTESY NATIONAL ATLAS
Some projections also use tears, or interruptions, to
minimize specific distortions. Unlike with a globe's gores,
these interruptions are strategically placed to group related
parts of the map together. For example, a Goode
homolosine projection uses four distinct interruptions that
cut through the oceans but leave major land masses
untouched.
A Goode projection of the Earth
IMAGE USED UNDER THE GNU FREE DOCUMENTATION
LICENSE
Different projections have different strengths and
weaknesses. In general, each projection can preserve
some, but not all, of the original qualities of the map,
including:
Area: Maps that show land masses or bodies
of water with the correct area relative to one
another are equal-area maps. Preserving the
correct area can significantly distort the shapes
of the land masses, especially for views of the
entire world.
Shapes: In the pseudoconical Robinson
projection, the continents are shaped correctly
and appear to be the correct size -- they look
"right." However, distances and directions are
incorrect on a Robinson projection. It's a good
tool for studying what the world looks like but
not for navigating or measuring distances.
Distances: Maps that maintain correct
distances between specific points or along
specific lines are equidistant maps.
Directions: Many navigational maps have
straight rhumb lines, or lines that intersect all of
the parallels or meridians from the same angle.
This means that, at any point on the map,
compass bearings are correct.
You can learn more about the specific map projections and
their strengths and weaknesses from NASA , the National
Atlas of the United States and the U.S. Geological Survey .
Choosing the right projection is just one part of creating a
successful map. Another is finding the right data. We'll
look at where map information comes from in the next
section.

How Maps Work

A map of the world's time zones.
It's easy to think of maps as sets of visual directions.
Whether you're trying to get to the top of Mount Everest or
to a friend's new home, a map can help you find your way.
But maps can do more than help you figure out where you
are and where you're going. They are representations of
information that can describe nearly anything about the
world.
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If you wanted to get an idea of which dog breeds are most
popular in different regions, you might spend days looking
at lists and charts. Or, you could look at a map and get an
instant grasp of the same information. Learning about the
physical features, imports, exports and population densities
of different countries would take ages if you relied on
written descriptions in a book. But with a map, all of the
numbers, patterns and correlations are right in front of you.
As Ian Turner, senior cartographer at GeoNova, puts it, "a
map is a type of language. It's a graphic language. It
presents information in hopefully a way that is very easy to
understand."
It's the job of a mapmaker, or cartographer, to put all of
this information into a format that people can understand
and learn from. Exactly what a person can learn depends
on the type of map. Most maps start with an outline of a
location, like a piece of land or a body of water. Then, they
provide information about the location's attributes.
Different maps incorporate different attributes. For
example:
Physical maps illustrate landforms like
mountains, deserts and lakes. With a physical
map, you can get a basic sense of what all or
part of the planet looks like and what its
physical features are. Physical maps usually
show differences in elevation through
hypsometric tints, or variations in color.
Topographic maps, on the other hand, illustrate
the land's shape and elevation using contour
lines.
Political maps display cultural information
about countries, their borders and their major
cities. Most political maps also include some
physical features, like oceans, rivers and large
lakes. You can check out political maps of the
world at our interactive atlas.
Thematic maps add information on a specific
theme, or subject. Examples of common themes
are population density, land use, natural
resources, gross domestic product (GDP) and
climate. Thematic maps can also show
extremely specialized information, such as the
availability of Internet access in different parts
of the world.
This combination of locations and attributes makes it
possible to put lots of information into a very small space.
A single map can show you all of the countries on a
continent, their borders, their approximate populations and
their primary imports and exports. People can also use
specialized thematic maps to analyze trends and patterns
in all kinds of data. A map showing communication costs in
different parts of the world, for example, could help a
nonprofit organization decide where to build a low-cost
wireless network. As Turner explains, "Maps geography
more than about capitals and countries - it's really about
how economics and climate and natural features, how all
the different variables that make up a society relate to one
another."
Common conventions help cartographers present all this
information in a way that makes sense. We'll look at them
in more detail in the next section.

Topographic Map Contour Lines

Contour lines are the greatest distinguishing feature of a
topographic map . Contour lines are lines drawn on a map
connecting points of equal elevation, meaning if you
physically followed a contour line, elevation would remain
constant. Contour lines show elevation and the shape of
the terrain. They're useful because they illustrate the
shape of the land surface -- its topography-- on the map.
Here's a cool way to understand how to interpret contour
lines: Take an object like a ball or a pile of laundry , and
shine a red laser pointer along the object's side. The line
you see will look like a contour line on a topographic map.
In order to keep things simple, topographic maps show
lines for certain elevations only. These lines are evenly
spaced apart. We call this spacing the contour interval. For
example, if your map uses a 10-foot contour interval, you
will see contour lines for every 10 feet (3 meters) of
elevation -- lines at 0, 10, 20, 30, 40, and so on. Different
maps use different intervals, depending on the topography.
If, for example, the general terrain is quite elevated, the
map might run at 80- to even 100-foot (24.4- to 30.5-
meter) intervals. This makes it easier to read the map --
too many contour lines would be difficult to work with.
Look in the margin of your map to find out its contour
interval.

To make topographic maps easier to read, every fifth
contour line is an index contour. Because it's impractical to
mark the elevation of every contour line on the map, the
index contour lines are the only ones labeled. The index
contours are a darker or wider brown line in comparison to
the regular contour lines. You'll see the elevations marked
on the index contour lines only. To determine elevations,
pay attention to the amount of space in between lines. If
the contours are close together, you're looking at a steep
slope. If the contours have wide spaces in between -- or
aren't there at all -- the terrain is relatively flat.

Topographic Map Scale

Another thing you need to understand about a topographic
map is scale. Obviously, maps aren't life-sized. Otherwise
we'd never be able to fit them in our backpacks. Instead,
cartographers plot maps on a ratio scale, where one
measurement on the map equals another larger amount in
the real world.
The first number of the scale is always one. It's your unit
of measurement, usually an inch. The second number is
the ground distance. For example, if your U.S. Geological
Survey (USGS) map has a scale of 1:24,000, it means that
one inch on the map is equal to 24,000 inches (2000 feet
or 609.6 meters) in the real world. Your map's scale legend
will always be at the bottom.
For USGS topographic maps, 1:24,000 is the scale most
often used. Maps based on metric units use a scale of
1:25,000, where one centimeter equals 0.25 kilometers.
You'll find most of the United States mapped at the
1:24,000 scale, with only a few exceptions. Puerto Rico, for
example, maps at 1:20,000 or 1:30,000 because the
country originally mapped at a metric scale. A couple of
states map at 1:25,000, and most of Alaska (due to its
size) maps at 1:63,360. The more populated areas of
Alaska, though, map at the typical 1:24,000 or 1:25,000.
A 1:24,000 map is large and provides a lot of detail about
the area -- it will include buildings, campgrounds, ski lifts,
among other things. You may also see footbridges and
private roads on a map of this scale.
It requires about 57,000 maps at this scale to cover the 48
contiguous United States, Hawaii and territories [source:
USGS]. However, you can find maps of various areas at all
different scales. The scale corresponds to its intended use.
For example, township engineers generally need extremely
detailed maps that show sewers, power and water lines,
and streets. The common scale for these maps is 1:600. If
you want to see one large area on a single sheet but with
less detail, a smaller scale map like 1:250,000 is better.

THEODOLITES SET-UP

THEODOLITES SET-UP

1. Place the instrument over the point with the tripod plate as level as possible and with two tripod legs on the downhill side, if applicable.
2. Stand back a pace or two and see if the  instrument appears to be over the station; if it does not, adjust the location and check again from a pace or two away.
3. Move to a position 90° opposed to the original inspection location and repeat step 2.
4. Check that the station point can now be seen through the optical plummet (or that the laser plummet spot is reasonably close to the setup mark). Then push the tripod legs firmly by pressing down on the tripod shoe spurs.
5. While looking through the optical plumb (or at the laser spot), manipulate the leveling screws (one, two or all the three at a time) until the cross hair (bull’s-eye) of the optical plummet or the laser spot is
directly on the station mark.
6. Level the theodolite circular bubble by adjusting the tripod legs up or down.
7. Perform a check through the optical plummet or note the location of the laser spot to confirm that it is still quite being over the station mark.
8. Turn one (or more) leveling screws to be sure that the circular bubble is now exactly centered (if necessary).
9. Loosen the tripod clamp bolt a bit and slide the instrument on the flat tripod top (if necessary) until the optical plummet or laser spot is exactly centered on the station mark. Retighten the tripod clamp bolt and reset the circular bubble, if necessary.

10. The instrument can now be precisely leveled by centering the tubular bubble.
Set the tubular bubble so that it is aligned in the same direction as two of the foot
screws. Turn these two screws (together or independently) until the bubble is
centered. Then turn the instrument 90°, at which point the tubular bubble will be
aligned with the third leveling screw.
Next, turn that third screw to center the bubble. The instrument now should be
level, although it is always checked by turning the instrument through 180°.
www.heroizutech.com.ng

What Survey Plan Is All About

What Survey Plan Is All About

A Survey Plan is a document that shows the boundary of a parcel of land. It gives an accurate measurement, description of the piece of land and contains the following
information: the name of the owner of the land surveyed, the address or description, the size and the drawn out portion as
mapped out on the survey plan document. Other information
that a survey plan contain includes: the beacon numbers, the
Surveyor who drew up the survey plan and the date it was
drawn and a stamp showing that the land is either free from
government acquisition or not. So how and why does one
chart a survey plan in Lagos?
The major reason why a survey plan is charted is to get what
is known as a Land Information. Before a transaction is
consummated over a plot of land, it is always advisable to
Chart the Survey Plan presented for the land to basically find
out whether it falls under government acquisition or not and
as well authenticate the claim of ownership to the land.
While Charting a Survey Plan can be done by private
individuals or organisations, it is also one of the procedures
involved in the issuance of Certificates of Occupancy or
Governor's Consent to persons who have applied for them at
the Lagos State Land Bureau.
The procedure for Charting a Survey Plan starts with
obtaining an Application Form for Land Information and
Payment Advice from the Accounts Department of the Office
of the Surveyor General at No.87 Awolowo Way, Ikeja. For
survey plans that carries a single name the fee for charting it
is N10, 000 and N1, 000 for development levy, while the fee
for one that carries Mr. and Mrs. is N20, 000 and N1, 000 for
development levy.
The next step is to go to the designated banks stated on the
payment advice, pay and obtain original receipt with teller
and then submit them along with the following documents at
the front desk office of the Surveyor General's Office: the
completed application form for land information and a copy
of the survey plan. A file for the application is then opened
at this stage.
From the front desk office, the file is sent to the Accounts
Department for verification of receipts of charting and
endorsement. If cleared, the file is sent to the Records Unit
for proper confirmation / screening of red copy. An Officer in
the Records Unit scrutinizes the red copy side by side with
the applicant's copy. File is then sent to Charting Room to
ascertain the status of the property (acquired or free from
government acquisition) and execute a composite plan to
affirm the authenticity of ownership. The Officer in Charge of
Charting does the verification and confirmation of charting
and the sends the result (a Land Information Certificate) to
the Director of Coordination, Transactions and Records
Department for final clearance. At the final stage, the result
is sent to the front desk office for filling and a text message
is sent to the applicant to come and pick up the Land
Information Certificate. On the average, the entire process takes between a month and two to complete.

The Relevance of a Survey Plan

The Relevance of a Survey Plan
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Some people like to ask ‘what is the relevance of a survey plan?’.
A survey plan’s primary purpose is to prove the identity of a land which comes handy when a dispute ensues.
A survey plan becomes of utmost importance for any success to be attained in any land suit. A plaintiff seeking for declaration of title to land has a cardinal duty to show with certainty, the area of land being claimed, failure to do so makes his or her claim to be at risk of being dismissed.
Hence, a land survey plan is a specialized map of a parcel of land, created by thoroughly examining and measuring the property. It determines and delineates boundary locations, building locations, physical features and other items of spatial importance.
More than just a diagram of the property, a land survey plan is an important legal document that displays the exact legal borders of the property and applicable aspects of the registered title.
The definition of a surveyor according to Section 2 of the Survey Act means a “Surveyor licensed or deemed to be licensed under the Surveyors Registration Council of Nigeria Act”
The purpose of a survey plan in a land dispute is to show graphically the morphology of an area in dispute, its extent and size. Where a plaintiff desires to draw up or cause to be drawn up a survey plan showing the land in dispute, such a plan must show clearly the dimensions of the land, the boundaries and other salient features. That is how delicate a survey plan is.
There are instances when a land survey plan becomes inconsequential in a land litigation or in the proper determination of issues arising from a land suit. The court considers in such instances the necessity of survey plan for the proper trial of the action. Therefore a survey plan is not necessary at the under-listed times;
1. When there is a proper identification of the disputed land via the evidences put forward or admitted into court.
2. Where the land in dispute is known to both parties or is clearly ascertainable whether from the averments in pleading or otherwise and its area, exact location and precise boundaries on the ground are either unmistakably and appropriately pleaded or are admitted or acknowledged by the defendant, the non-production in evidence of the survey plan of such land cannot be a matter of great moment and does not dis-entitle the plaintiff from maintaining an action in respect of title, trespass or injunction over such land.
However, a survey plan becomes necessary when the following arise:
1.It is settled law that, where the identity of the land in dispute is in dispute, there is need to produce a survey plan particularly if the facts produced in evidence cannot establish with certainty, the identity of the said land.
2. Where parties file different survey plans on both side, it will be the duty of the party who disputes the identity of the land (and who wants to succeed), to file a composite plan where it becomes necessary or as the court may direct at the trial. The purpose of filing a composite plan is to fix and delimit the land in dispute
3. Where a plaintiff pleads and serves the defendant a survey plan which is subsequently admitted in evidence as exhibit and which shows the boundaries and features on the land in dispute, this will constitute sufficient proof of the boundaries and features set out in the land in dispute.
A defendant who intends to challenge or dispute such boundaries or features as shown in the survey plan must do so by specifically traversing the plaintiff’s pleading in that regard, because a mere general traverse will be insufficient.
In the event that a plaintiff tenders a survey plan of the land in dispute, and the plan is admitted without objection while the defendant fails to file a counter claim, the defendant cannot be heard to contend that the plaintiff did not prove with certainty the.
#ALWAYS_CONSULT_A_SURVEYOR_NOT_A_ QUACK