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... Goals of this Workshop 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 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...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 1
Maps, Plans...ways they are used A Map is not the Territory -Alford Korzybski Go from the general to the specific Maps are 2-dimensional representations of complex landscapes at one point in time! Key Elements of Maps Key Elements of Maps North Arrow For orientation purposes! " Identifiers! " Legends! " Scale Key Elements of Maps Key Elements of Maps Title Block Information on who/what/when etc Legends Provide a guide to the symbols used 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 2
Key Elements of Maps Key Elements of Maps Scale Shows relative size of objects Scale Shows relative size of objects Written Scale Graphical Scale 20! 35 1:12,000 (ratio) 1 = 1,000 (equivalent) Graphic scales are the most reliable! Beware of Xerox Distortion Measuring Distances! " Rulers and Scales Measuring Distances! " 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 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 Measuring Distances Engineering Scales X 2 400 X 2 = 800 ft PLAN SCALE = 40 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 1 = 100 ft 200 1 = 200 ft 2000 1 = 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 1 =40 Land Use Academy 3
Measuring Distances Factoid: What is an acre? 200 Distance? 55 200 1 =40 Builder s acre = 40,000 sq. ft (R-40) True acre 9% larger = 43,560 sq. ft. (R-1) Map Reading Skills Maps Wonder what those lines mean? 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 This could be the edge of a presented map Land Use Academy 4
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 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. - Tips a series of concentric contours ending in a small closed circle or oval shows a local hilltop contour lines of a ridge are in a U that always points downhill contours close together show a steep slope contours very close together show a cliff Water flows downhill... green areas show forest cover; white areas denote fields contours at a stream form a V that always points uphill Topography Slope direction is calculated perpendicular to the contour lines. Slope Change of elevation between two points, over a given distance Water flows downhill... Because it is the steepest slope. Elevation Distance Slope Land Use Academy 5
Slope Why is Slope Important? Percent Slope = Change in Elevation Distance X 100 If too Steep: - potential erosion - soil stability - safety 10 ft 20 ft 10 ft (10 / 20 ) X 100 = 50% slope 20 ft Why is Slope Important? Your turn! If too flat: - storm water may not drain - may flood 20 ft 0 ft 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? Answers As the map is rolled out at the P&Z meeting... 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? Hmm. What are they doing? 9."Where would that water leave the map edge? Land Use Academy 6
Evaluating the Project Land Clearing 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
Grading Grading Existing Contour Lines Existing Contour Lines More level when contours are farther apart Proposed Contours Structures Other Structures " " Type Size " " Septic Systems Wells " Location " Roof leaders " Footing drains 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 8
5/4/12 Types of Plans who? what? where? when?! " 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 Where is it? What s the project name? Where s TAKE IT APART north? & START ASKING QUESTIONS Type of Map? What s the scale? When drawn? What s it all Mean? Who made the map? Are they qualified? take it apart take it apart and Find the roads the centerline sidewalks of road right-of-way Property Line Stream take it apart take it apart Topography wetland review area 602+ 2 Land Use Academy 9
take it apart take it apart Topography 100-Yr Flood take it apart take it apart Vegetation & Stonewalls Utilities put it back together 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 Inland/Wetland Commission: " Review site plans and subdivisions to determine impact to wetlands Land Use Academy 10
Proposal 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? Is this a copy? Is that really the scale? To ask as many questions as it takes 03/12/ 05 take it apart take it apart 03/12/0 5 03/12/ 05 focus in What s the lot size? ask questions Regulations: 1 ac. Lot is 1.34 ac. Land Use Academy 11
Is that enough frontage? Regulations: 100 min. Is the building within setbacks? Regulations: 40 front 10 side 122 131 27 40 46 Double Frontage How many parking spaces? Regulations: 41 + 2 Where s the limit of wetland review? 34 + 2 9 2 4 5 8 8 Did Inland / Wetland Commission approve? What s the distance from the intersection? Regulations: 75 Where s the dumpster? 62 108 Is it screened? Can it be accessed easily? Land Use Academy 12
Is that a drive-up? Are drive-ups permitted here? Other questions? Does drive-up queue conflict with parking? 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 Another Proposal It s Your Turn Again! LP Answers for Exercise 2 HP 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. 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, it s 920 in length 11. What other questions do you have? Questions?? Land Use Academy 13
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. 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?! " If in doubt, ASK! If still in doubt, ask again! Land Use Academy 14