5/4/12
Map Reading 101:
Using and Reading Maps and Plans
Paula Stahl, LLA, ASLA, AICP
Land Use Educator
Green Valley Institute
A Key Skill for Land Use
Commissioners
How most of us react to
maps and reports...
Wonder what
those lines
mean?
As the map is
rolled out at
the P&Z
meeting...
Where is
this ?
Goals of this Workshop
Im
hungry.
Oh, geeze Ill
never get
home in time
for the game
Maps, Plans...Whats the Difference?
! "
! "
Maps show physical features of the
natural or built environment at
established scale and orientation.
Plans are engineered drawings made
to scale showing existing physical
features of a site and proposed
changes to accommodate
development.
Land Use Academy
To Understand:
! "
the sources of maps and plans
! "
how maps and plans are used
! "
fundamental elements of maps and plans
! "
how to evaluate maps and plans
Maps, Plans...Whats the Difference?
What is the purpose of this Map or Plan?
! "
Town Planning
! "
Regulatory
! "
Wetland Impacts (IWW)
! "
Subdivision (Planning)
! "
Site Plan (Zoning)
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5/4/12
Maps, Plans...ways they are used
Go from the general to the specific
Key Elements of Maps
A Map is not the Territory…
-Alford Korzybski
Maps are 2-dimensional representations of
…at one point in time!
complex landscapes…
Key Elements of Maps
North Arrow For orientation purposes
! "
Identifiers
! "
Legends
! "
Scale
Key Elements of Maps
Key Elements of Maps
Title Block
Legends Provide a guide to the symbols used
Information on who/what/when etc
XYZ GROUP/
ABC ASSOCIATES
500 Longitude Boulevard
Mapville, Connecticut 06001
860-555-5555
Cartography Road
Mapville, CT
Title
Creation & Revision
Dates
Source
Land Use Academy
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5/4/12
Key Elements of Maps
Scale
Key Elements of Maps
Scale
Shows relative size of objects
Shows relative size of objects
Written Scale
Graphical Scale
1:12,000 (ratio)
35
20!
1 = 1,000 (equivalent)
Graphic scales are the most reliable!
Beware of Xerox Distortion
Measuring Distances
! "
Measuring Distances
! "
Rulers and Scales
Engineering Scales
40 ft
240 ft
400 ft
Engineering Scale
1 = 10
1 = 20
1 = 30
1 = 40
1 = 50
1 = 60
Architects Scale
1/8 = 1
1/4 = 1
1/2 = 1
3/4 = 1
1 = 1
Measuring Distances
Map Scale
Meaning
10
1 inch = 10 ft
20
1 inch = 20 ft
30
1 inch = 30 ft
40
1 inch = 40 ft
50
1 inch = 50 ft
60
1 inch = 60 ft
Measuring Distances
Engineering Scales
PLAN SCALE = 40
400 X 2 = 800 ft
X2
But, can be
used at other scales
Plan Scale
Meaning
10
1 inch = 10 ft
20
1 inch = 20 ft
30
Scale
Meaning
Adjustment
80
1 = 80 ft
Use 40 scale and
multiply by 2
1 inch = 30 ft
100
1 = 100 ft
Use 10 scale and
add a zero
40
1 inch = 40 ft
200
1 = 200 ft
50
1 inch = 50 ft
Use 20 scale and
add a zero
60
1 inch = 60 ft
2000
1 = 2000 ft
Use 20 scale and
add 2 zeros
Land Use Academy
1=40
3
5/4/12
Factoid: What is an acre?
Measuring Distances
200
ce
tan
Dis
?
200
55
Builders acre = 40,000 sq. ft (R-40)
True acre 9% larger = 43,560 sq. ft. (R-1)
1=40
Map Reading Skills
Wonder what
those lines
mean?
Maps
Many maps are in the
form of topographical
maps aka topo
Interpreting a 3D
world in 2D
Topography
Topography
Contours: an imaginary line that
connects points of equal elevation
Contours always connect,
but not always within the map boundaries...
Index Contours are the lines labeled with an elevation
Contour Interval is the difference between lines,
USGS topo has 10 ft contours and site plans 2 ft contours
Land Use Academy
This could be
the edge of a
presented map
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5/4/12
Topography
Topography
Cross-sections are sometimes used to represent 3-D objects
in 2 dimensions.
Cross-sections are sometimes used to represent 3-D objects
in 2 dimensions.
Vertical scale sometimes
exaggerated to better show change
a spot elevation is a point
of known elevation used as
a pt of reference for
surveys.
a contour interval is the vertical
distance b/w contours. 10 on
topos; 2-5 on site plans
every 5th contour is an index
contour shown in bold
Plan Reading - Tips
a benchmark (BM): point of
known position & elevation
used as a pt of reference
for surveys.
contours far apart show a
gentle slope
contours close together
show a steep slope
a series of concentric contours
ending in a small closed circle
or oval shows a local hilltop
contours very close
together show a cliff
Water flows
downhill...
contour lines of a ridge are in a
U that always points downhill
green areas show forest cover;
white areas denote fields
contours at a stream form a
V that always points uphill
Topography
Slope
Slope direction is calculated perpendicular to
the contour lines.
Change of elevation between two
points, over a given distance…
Land Use Academy
Because …
it is the steepest
slope.
Distance
Elevation
Water flows
downhill...
pe
Slo
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5/4/12
Slope
Why is Slope Important?
Percent Slope = Change in Elevation
Distance
X 100
If too Steep:
- potential erosion
- soil stability
- safety
20 ft
10 ft
10 ft
(10 / 20 ) X 100
50% slope
=
Why is Slope Important?
If too flat:
20 ft
Your turn!
Find or calculate the following:
- storm water may not drain
- Whats missing?
- Highest elevation
- Elevation of Pt. A
- The distance between Pts A & B
- The change in elevation between A & B
- The percent slope between A & B
-" Which is higher C or D?
-" Which direction would water flow from C? D?
-" Where would that water leave the map edge?
- may flood
0 ft
20 ft
Answers
As the map is rolled out at the P&Z meeting ...
1."-Whats missing?
North Arrow, Legend, Source
2."-highest elevation
582 ft
Hmm. What are
they doing?
3."-elevation of Pt. A
570 ft
4."-the distance between Pts A & B
1,000 ft
5."-the change in elevation between A & B
100 ft [B is 470]
6."- the percent slope between A & B
10%
100/1000 = .1
7."Which is higher C or D?
C [C is 510]
8."Which direction would water flow from C? D?
9."Where would that water leave the map edge?
Land Use Academy
6
5/4/12
Land Clearing
Evaluating the Project
Site Development
•" Land Clearing
•" Grading
•" Roads
•" Structures
Management Plans
•" Erosion & Sedimentation
•" Stormwater
Land Clearing
Grading
Limit of Construction Activity
Grading
Grading
Land Use Academy
7
5/4/12
Grading
Grading
Existing Contour Lines
Existing Contour Lines
More level when contours
are farther apart
Proposed
Contours
Structures
Other Structures
•"
Type
•"
Septic Systems
•"
Size
•"
Wells
•"
Location
•"
Roof leaders
•"
Footing drains
Other Structures
Land Use Academy
Maps, Plans… Whats the Difference?
! "
Maps show physical features of the
natural or built environment at
established scale and orientation
! "
Plans are engineered drawings, made to
scale, showing existing physical features
of a site and proposed changes to
accommodate development.
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5/4/12
Plan Reading
Types of Plans
! "
! "
! "
! "
! "
! "
! "
! "
who? what? where? when?
Where is it?
Survey – the site before proposed intervention
Layout – the proposed locations of added features
Grading & Drainage – changes to topography
Utilities – location/connection to systems
Demolition Plan – whats being torn down
Planting Plan – what plants where
Details – drawings of specific features at a large scale
Erosion and Sediment Control Plan –
Whats the project
name?
Wheres
north?
TAKE IT APART &
Whats the scale?
START ASKING
When drawn?
QUESTIONS
Type of Map?
Whats it all Mean?
Who made the map?
Are they qualified?
03/12/05
protection of the site and any wetlands during construction
Plan Reading – take it apart
Plan Reading – take it apart
Stream
Property Line
Find centerline
the roads
and
and the
sidewalks of road right-of-way
03/12/05
Plan Reading – take it apart
03/12/05
Plan Reading – take it apart
Topography
we
tla
nd
re
vie
w
ar
ea
602
03/12/05
Land Use Academy
+2
03/12/05
9
5/4/12
Plan Reading – take it apart
Plan Reading – take it apart
100-Yr Flood
Topography
03/12/05
Plan Reading – take it apart
03/12/05
Plan Reading – take it apart
Vegetation & Stonewalls
Utilities
03/12/05
Plan Reading
–
put it back together
03/12/05
Plan Reading
– Who & Why
Zoning Commission:
•" Establish zoning regulations
•" Review site plans for adherence
LP
HP
Planning Commission:
•" Plan of Conservation & Development
•" Establish Subdivision regulations
•" Review plans for subdivisions
03/12/
05
Land Use Academy
Inland/Wetland Commission:
•" Review site plans and subdivisions to determine
impact to wetlands
10
5/4/12
Plan Reading –
Plan Reading –
Proposal
Why are you looking at these plans?
There is a proposal to change this site
Whats your role as a commissioner?
To make sure this proposal meets the requirements
set out by your commission's regulations
Is this a copy?
Is that really the scale?
Whats your goal?
03/12/
05
To ask as many questions as it takes
Plan Reading
Plan Reading
take it apart
take it apart
03/12/0
5
Plan Reading
focus in
03/12/
05
Plan Reading
Whats the lot size?
ask questions ……
Regulations: 1 ac.
Lot is 1.34 ac.
Land Use Academy
11
5/4/12
Plan Reading
Plan Reading
Is that enough frontage?
Regulations: 100 min.
Is the building within setbacks?
Regulations:
40
front
10 side
27
122
131
46
40
Double Frontage
Plan Reading
Plan Reading
How many parking spaces?
Regulations: 41 + 2
Wheres the limit of wetland review?
34 + 2
2
9
5
4
8
8
Did Inland / Wetland Commission approve?
Plan Reading
Whats the distance from the intersection?
Plan Reading
Regulations: 75
Wheres the dumpster?
62
108
Land Use Academy
Is it screened?
Can it be accessed easily?
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5/4/12
Plan Reading
Plan Reading
Is that a drive-up?
Are drive-ups permitted here?
Other questions?
Does drive-up queue conflict with parking?
Plan Reading – Another Proposal
Plan Reading – Another Proposal
Subdivision
The division of a tract or parcel of land into three or more parts or lots for the purpose, whether
immediate or future, of sale or building development expressly excluding development for municipal,
conservation or agricultural purposes
Its Your Turn Again !
Answers for Exercise 2
1. Is anything missing from the Layout Plan?
Professional Seal & Signature
2. Whats the scale of the Layout Plan?
100 scale
Questions??
3. Where are the steeper slopes? the flattest
area?
LP
4. Locate the High and Low Points
HP LP
How does water flow from the HP to the LP?
5. Would Inland/Wetlands need to approve?
Yes
Outline the upland regulated area.
HP
6. What type of subdivision is this?
R-1/2 Open Space
7. If an Open Space subdivision, is there
sufficient open space set aside?
Yes 8.18 ac. out of 15.65 ac.
8. Do all proposed lots meet the minimum lot
size?
Yes
9. Do all the proposed lots meet the minimum
frontage required?
Yes, the narrowest is 78
10. Does the length of this new cul-de-sac road
meet regulations?
Yes, its 920 in length
11. What other questions do you have?
Land Use Academy
13
5/4/12
Key Concepts:
! "
Know the purpose of your map or plan
! "
Remember: The map is not the territory.
Verify with field walks, if necessary.
! "
Always look for the significant map elements:
north arrow, title blocks, legends, etc.
! "
Always ask: what is the scale of this map?
Is it appropriate for the purpose?
! "
Try to visualize topography…use tricks when necessary.
! "
The maps and plans are YOURS! Draw on them, make
notes, anything that will help you formulate questions
and understand the proposal.
! "
If in doubt, ASK! If still in doubt, ask again!
Land Use Academy
Whats the
frontage?
Is that
enough for
a sight line?
I think theyre
actually
reading my
maps!
How steep
is that
slope ?
The next time the map
is rolled out at the P&Z
meeting...
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