Map Reading 101: Using and Reading Maps and Plans

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1 Map Reading 101: Using and Reading Maps and Plans A Key Skill for Land Use Commissioners Paula Stahl, LLA, ASLA, AICP Land Use Educator Green Valley Institute Land Use Academy 1

2 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? I m hungry. Oh, geeze I ll never get home in time for the game Goals of this Workshop 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 Land Use Academy 2

3 Maps, Plans...What s 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. Maps, Plans...What s the Difference? What is the purpose of this Map or Plan? Town Planning Regulatory Wetland Impacts (IWW) Subdivision (Planning) Site Plan (Zoning) Land Use Academy 3

4 Maps, Plans...ways they are used Go from the general to the specific A Map is not the Territory -Alford Korzybski Maps are 2-dimensional representations of complex landscapes at one point in time! Land Use Academy 4

5 Key Elements of Maps Identifiers Legends Scale Key Elements of Maps North Arrow For orientation purposes Land Use Academy 5

6 Key Elements of Maps Title Block Information on who/what/when etc XYZ GROUP/ ABC ASSOCIATES 500 Longitude Boulevard Mapville, Connecticut Cartography Road Mapville, CT Title Creation & Revision Dates Source Key Elements of Maps Legends Provide a guide to the symbols used Land Use Academy 6

Scale Graphical Scale 1:12,000 (ratio) 1 = 1,000 (equivalent)

7 Key Elements of Maps Scale Shows relative size of objects 20! 35 Key Elements of Maps Scale Shows relative size of objects Written Scale Graphical Scale 1:12,000 (ratio) 1 = 1,000 (equivalent) Graphic scales are the most reliable! Beware of Xerox Distortion Land Use Academy 7

Engineering Scales 40 ft 240 ft 400 ft Map Scale Meaning 10 1 inch = 10 ft 20 1 inch =

8 Measuring Distances Rulers and Scales 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 Engineering Scales 40 ft 240 ft 400 ft 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 Land Use Academy 8

9 Measuring Distances Engineering Scales X X 2 = 800 ft But, can be used at other scales Plan 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 Scale Meaning Adjustment 80 1 = 80 ft = 100 ft = 200 ft = 2000 ft Use 40 scale and multiply by 2 Use 10 scale and add a zero Use 20 scale and add a zero Use 20 scale and add 2 zeros Measuring Distances PLAN SCALE = 40 1 =40 Land Use Academy 9

10 Measuring Distances Distance? 55 1 =40 Factoid: What is an acre? Builder s acre = 40,000 sq. ft (R-40) True acre 9% larger = 43,560 sq. ft. (R-1) Land Use Academy 10

11 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 Land Use Academy 11

Topography Contours: an imaginary line that connects points of equal elevation Index Contours are the lines labeled with an elevation Contour Interval is the difference between lines, USGS

12 Topography Contours: an imaginary line that connects points of equal elevation 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 Topography Contours always connect, but not always within the map boundaries... This could be the edge of a presented map Land Use Academy 12

13 Topography Cross-sections are sometimes used to represent 3-D objects in 2 dimensions. Topography Cross-sections are sometimes used to represent 3-D objects in 2 dimensions. Vertical scale sometimes exaggerated to better show change Land Use Academy 13

a contour interval is the vertical distance b/w contours.

bold contours far apart show a gentle slope a spot elevation is a point of

a benchmark (BM): point of known position & elevation used as a pt of

a series of concentric contours ending in a small closed circle or oval shows

close together show a cliff contour lines of a ridge are in a U that always

14 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 contours far apart show a gentle slope a spot elevation is a point of known elevation used as a pt of reference for surveys. a benchmark (BM): point of known position & elevation used as a pt of reference for surveys. a series of concentric contours ending in a small closed circle or oval shows a local hilltop contours close together show a steep slope contours very close together show a cliff 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 Plan Reading - Tips Water flows downhill... Land Use Academy 14

15 Topography Slope direction is calculated perpendicular to the contour lines. Water flows downhill... Because it is the steepest slope. Slope Change of elevation between two points, over a given distance Distance Elevation Slope Land Use Academy 15

16 Slope Percent Slope = Change in Elevation Distance X ft 20 ft (10 / 20 ) X 100 = 50% slope Why is Slope Important? If too Steep: - potential erosion - soil stability - safety 10 ft 20 ft Land Use Academy 16

A - The distance between Pts A & B - The change in elevation between A &

17 Why is Slope Important? If too flat: - storm water may not drain - may flood 20 ft 0 ft Your turn! Find or calculate the following: - What s 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? Land Use Academy 17

18 Answers 1. -What s missing? North Arrow, Legend, Source 2. -highest elevation 582 ft 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? As the map is rolled out at the P&Z meeting... Hmm. What are they doing? Land Use Academy 18

19 Evaluating the Project Site Development Land Clearing Grading Roads Structures Management Plans Erosion & Sedimentation Stormwater Land Clearing Land Use Academy 19

20 Land Clearing Limit of Construction Activity Grading Land Use Academy 20

21 Grading Grading Land Use Academy 21

22 Grading Existing Contour Lines More level when contours are farther apart Grading Existing Contour Lines Proposed Contours Land Use Academy 22

23 Structures Type Size Location Other Structures Septic Systems Wells Roof leaders Footing drains Land Use Academy 23

24 Other Structures Maps, Plans What s 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 24

Types of Plans Survey the site before proposed intervention Layout the proposed locations of added features

torn down Planting Plan what plants where Details drawings of specific features at a large scale Erosion and

when? Where is it? What s it all Mean? What s the project name? Where s TAKE IT APART north?

25 Types of Plans 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 what s being torn down Planting Plan what plants where Details drawings of specific features at a large scale Erosion and Sediment Control Plan protection of the site and any wetlands during construction Plan Reading who? what? where? when? Where is it? What s it all Mean? What s the project name? Where s TAKE IT APART north? & START ASKING QUESTIONS Type of Map? What s the scale? When drawn? Who made the map? Are they qualified? 03/12/05 Land Use Academy 25

26 Plan Reading take it apart and centerline of road right-of-way Find the roads and the sidewalks 03/12/05 Plan Reading take it apart Property Stream Line 03/12/05 Land Use Academy 26

27 Plan Reading take it apart 03/12/05 Plan Reading take it apart Topography /12/05 Land Use Academy 27

28 Plan Reading take it apart Topography 03/12/05 Plan Reading take it apart 100-Yr Flood 03/12/05 Land Use Academy 28

29 Plan Reading take it apart Vegetation & Stonewalls 03/12/05 Plan Reading take it apart Utilities 03/12/05 Land Use Academy 29

30 Plan Reading put it back together LP HP 03/12/ 05 Plan Reading Who & Why Zoning Commission: Establish zoning regulations Review site plans for adherence Planning Commission: Plan of Conservation & Development Establish Subdivision regulations Review plans for subdivisions Inland/Wetland Commission: Review site plans and subdivisions to determine impact to wetlands Land Use Academy 30

31 Plan Reading Why are you looking at these plans? There is a proposal to change this site What s your role as a commissioner? To make sure this proposal meets the requirements set out by your commission's regulations What s your goal? To ask as many questions as it takes Plan Reading Proposal Is this a copy? Is that really the scale? 03/12/ 05 Land Use Academy 31

32 Plan Reading take it apart 03/12/0 5 Plan Reading take it apart 03/12/ 05 Land Use Academy 32

33 Plan Reading focus in Plan Reading What s the lot size? ask questions Regulations: 1 ac. Lot is 1.34 ac. Land Use Academy 33

34 Plan Reading Is that enough frontage? Regulations: 100 min Double Frontage Plan Reading Is the building within setbacks? Regulations: 40 front 10 side Land Use Academy 34

35 Plan Reading How many parking spaces? Regulations: Plan Reading Where s the limit of wetland review? Did Inland / Wetland Commission approve? Land Use Academy 35

36 Plan Reading What s the distance from the intersection? Regulations: Plan Reading Where s the dumpster? Is it screened? Can it be accessed easily? Land Use Academy 36

37 Plan Reading Is that a drive-up? Are drive-ups permitted here? Does drive-up queue conflict with parking? Plan Reading Other questions? Land Use Academy 37

or building development expressly excluding development for municipal, conservation or

38 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 Plan Reading Another Proposal It s Your Turn Again! Land Use Academy 38

LP Answers for Exercise 2 1. Is anything missing from the Layout Plan? Professional Seal & Signature 2. What s the scale of the Layout Plan? 100 scale 3. Where are the steeper slopes?

39 LP Answers for Exercise 2 1. Is anything missing from the Layout Plan? Professional Seal & Signature 2. What s the scale of the Layout Plan? 100 scale 3. Where are the steeper slopes? the flattest area? 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 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 Does the length of this new cul-de-sac road meet regulations? Yes, it s 920 in length 11. What other questions do you have? Questions?? Land Use Academy 39

40 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! What s the frontage? The next time the map is rolled out at the P&Z meeting... Is that enough for a sight line? I think they re actually reading my maps! How steep is that slope? Land Use Academy 40

Topographic Maps. Take Notes as you view the slides

Topographic Maps. Take Notes as you view the slides Topographic Maps Take Notes as you view the slides Lesson Objectives Define a topographic map and state its uses. Describe how contour lines show the elevations, shape, and slope of the land. Identify