building Information Technology Skills
lessons

Unit 3
Lesson 1
Scale and Community Mapping


Objectives

Cartographic scale can be defined as the ratio of the distance between two points on a map to the real distance between the two corresponding Cartesian coordinates portrayed (source: Columbia free dictionary online). We will analyze the scale that you used to draw your community maps and overlays during the last two weeks.

Materials

Community maps and layers drawn during the past two weeks

T-Square
Two different colored pencils
Vellum

Procedure

1.  Use a new sheet of vellum paper to create a new layer that we will use to analyze the distance portrayed on your community map. Register the layer using the registration points depicted on your base community map.

 

2.  Draw a grid using one of the two colored pencils you selected.  Use the t-square to draw inch tick marks on the left and right hand sides of the vellum. Connect the tick marks using the ruler. Use the t-square to draw inch tick marks on the top and bottom of the vellum page. Connect the tick marks using a ruler.  Your vellum layer should now be covered by a one inch square grid in one color. 

3.  Using the second colored pencil, draw four line segments connecting two point features from the base map on the new layer.  Label each segment  numerically. Measure the number of inches for each line segment and note the total next to each segment.  

4.  Using Google Earth, zoom in on the area that is depicted by the community map that you drew. Make sure that the entire map fits within the area on your computer screen. 

5.  Select the measure tool on the Google Earth menu. Use the tool to measure the real world distance for each of the four segments you drew on your vellum layer.  Note the distance on the layer next to each line segment. 

6.  For each of the four segments, divide the real world distance by number of inches drawn to find out how much distance is equated with one inch.  Express the scale for each line segment by completing this ratio:

                         one inch =  ?  miles

Discussion Questions

1.  Are the scales for each segment the same? Why or why not?

2.  How accurate was your community map in terms of scale? Discuss.

3.  How might you go about re-drawing the community map with one consistent scale?

4.  Could you redraw the map at a smaller or larger scale? If so, how?

Lesson Two