1. 1. Common Radon Mitigation Methods
Soil Suction
Draws radon from beneath the house and vents it away from the house through pipes.
Sealing Cracks & Openings
Sealing alone doesn't usually lower radon levels, but it can limit the flow of radon into a home and
reduce the loss of air that's been conditioned, so it helps make other types of reduction techniques
more effective.
House Pressurization
This method uses a fan to create pressure differences that help keep radon from entering the
house.
Heat Recovery Ventilator (HRV)
Installed to increase ventilation, HRV uses the heated or cooled air being exhausted to warm or
cool the incoming air. This type of system is most effective when used to ventilate only the
basement of a house. Heating and cooling costs will likely rise when this type of system is in place.
Eliminating Radon in Water
If you've determined that your private water supply is your home's source of radon, it can be
fixed.
Point-of-entry treatments use charcoal filters or aeration devices to remove radon from water before it enters your home.
Point-of-use devices remove radon at the tap, so you won't ingest it. They do nothing to reduce radon in unfiltered taps,
such as your tubs, showers, and laundry areas, so radon in the air may remain high.
Radon Mitigation for Existing Homes
Your mitigation contractor can offer complete details about different types of radon reduction
systems. After performing tests to determine how radon is entering your home the contractor will
be in a better position to recommend the "best" system for your house. Costs vary, but most
systems can be installed for $1,000-$2,500.
Radon Mitigation for New Homes
If you're building a new home, now is the time to install a radon reduction system. The cost is far
less than fitting a system after the home is built, and having the system in place will be a good
selling point later.

2. 2. A contour map has lines that show elevation. Any point on any line is at the
same elevation. Let's say you have a map that includes a coastline and the
lines are at 200 foot intervals. There would be lines at 200, 400, 600, 800, etc
feet. You can see hills (the lines form circles), whether a slope is gradual or
steep (where it's steep the lines are close together), and other features. Once
you're used to one, it almost makes the map look 3-D.
The distinctive characteristic of a topographic map is that the shape of the
Earth's surface is shown by contour lines. Contours are imaginary lines that
join points of equal elevation on the surface of the land above or below a
reference surface such as mean sea level. Contours make it possible to
measure the height of mountains, depths of the ocean bottom, and steepness
of slopes.
A topographic map shows more than contours. The map includes symbols
that represent such features as streets, buildings, streams, and woods
contour map will show the contours, or curves of the ground--i.e. elevation
lines. They are helpful in letting you know you're on the right route. After
figuring out your azimuth to get from point a to point b it's reassuring to know
the maps says you're supposed to be walking up a hill and you actually are.
You're in trouble if you look around and there's a ravine you have to cross but
it's not where you thought you should be on the map.
For pilots it lets them know just how high the ground is going to be so they
can fly over and not into it. Same for boat pilots and the bottom of the body of
water they're on.
Topographic maps are frequently paired with handheld GPS devices, sports &
fitness GPS devices, and smartphone applications.
"Topo" maps provide highly detailed information about the natural and man-made
aspects of the terrain, but are best known for their series of contour lines that show
elevation changes, and colors
signifying varying land types and bodies of water. Topographic maps in their
paper form have been in use for many years, and are a mainstay of
outdoorspeople and those who must understand landscape details for
business purposes.
Topographic maps are increasingly stored, transmitted, and used in digital
format. For example, Garmin and DeLorme offer dozens of topo mapsets that
may be purchased on DVD, SD card, or via direct download.
Topographic maps come in different scales, and the differences are important.
For example, the common "24K" topo map is in the scale of 1:24,000 (1 inch =

3. 2,000 feet) and shows great detail. The 24K map is also known as a "7.5
minute" map, because it covers 7.5 minutes of latitude and longitude. Another
common format, the "100K" topo map, is in the scale of 1:100,000 (1
centimeter = 1 kilometer) and shows less detail, but covers a wider area than
the 24K topo.
Contour maps are very useful since they provide valuable information about
the terrain. Some of the uses are as follows:
i) The nature of the ground and its slope can be estimated
ii) Earth work can be estimated for civil engineering projects like road works,
railway, canals, dams etc.
iii) It is possible to identify suitable site for any project from the contour map of
the region.
iv) Inter-visibility of points can be ascertained using contour maps. This is
most useful for locating communication towers.
v) Military uses contour maps for strategic planning.
3. System of tacheometry
Depending on the type of instrument and methods/types of observations, tacheometric
measurement systems can be divided into two basic types:
(i) Stadia systems and
(ii) Non-stadia systems
Stadia systems:
In this systems staff intercepts, at a pair of stadia hairs present at diaphragm, are considered. The
stadia system consists of two methods:
1. Fixed-hair method:
In this method, stadia hairs are kept at fixed interval and the staff interval or intercept
(corresponding to the stadia hairs) on the leveling staff varies. Staff intercept depends upon the
distance between the instrument station and the staff.
2. Movable-hair method:
In this method, the staff interval is kept constant by changing the distance between the stadia
hairs. Targets on the staff are fixed at a known interval and the stadia hairs are adjusted to bisect
the upper target at the upper hair and the lower target at the lower hair. Instruments used in this
method are required to have provision for the measurement of the variable interval between the
stadia hairs. As it is inconvenient to measure the stadia interval accurately, the movable hair
method is rarely used.

4. Non stadia systems:
This method of surveying is primarily based on principles of trigonometry and thus telescopes
without stadia diaphragm are used. This system comprises of two methods:
(i) Tangential method
In this method, readings at two different points on a staff are taken against the horizontal cross
hair and corresponding vertical angles are noted.
(ii) Subtense bar method.
In this method, a bar of fixed length, called a subtense bar is placed in horizontal position. The
angle subtended by two target points, corresponding to a fixed distance on the subtense bar, at
the instrument station is measured. The horizontal distance between the subtense bar and the
instrument is computed from the known distance between the targets and the measured horizontal
angle.