Introduction to Physical Geography
Instructor/Chaddock
Homework Assignment #1
Page 3 of 4
Homework Assignment #1: An Introduction to Map Reading and Interpretation: Working with an Atlas and Topographic Maps
Part 1: Working with an Atlas
To complete Part 1, you will need access to a copy of the Goode’s World Atlas, 19th edition (or newer). The Goode’s World Atlas is available for purchase at the Cuyamaca Bookstore, or you may check out a copy from the library (available on reserve under my name (Chaddock: Geog. 120) for 3 hour in library use only.)
This exercise is designed for you to become comfortable when using an atlas. There is an index near the back of the atlas and a world map near the front that can be used to figure out where in the world you are if you become disoriented as you move through the questions. Make sure all answers involving latitude and longitude include degrees and hemispheres.
Example: San Diego County is located at approximately 33˚ N, 117˚ W.
Please do not hesitate to make an appointment to see me if you need any help.
Please refer to the map of India (pp. 186-187 of the Goode’s 19th edition; pp. 202-203 of the Goode’s 20th and 21st editions) to answer questions 1-3 below:
- What is the Written Scale of this map?______
- Of the following projections, which was used to make this map:
Cylindrical, Conic, or Planar?
- Please compare the South America map (page 128 of the Goode’s 19th edition; page 139 of the Goode’s 20th and 21st editions) to the map of India. Which of these two maps has the smaller scale?
4. If the clock time in San Diego, California is 9:00 am Standard Time, what clock time is it in London, England? (HINT: the World Time Zones map may be helpful; page xii in of the Goode’s 19th and 20th editions; page 66 of the Goode’s 21st edition.)
5. What U.S. State is located south of the Tropic of Cancer?______
6. What parallel of latitude delineates the border between California and Oregon?
- What meridian of longitude delineates the border between California and Nevada?
- What group of islands is located at the intersection of the Equator and the 90th meridian of longitude west?
Part II: Working with the Geographic Grid System on Topographic Maps
To complete Part II, you will need access to the following United States Geological Survey (USGS) 7.5 Minute Topographic Maps: 7.5’ El Cajon Quadrangle; 7.5’ Dulzura Quadrangle. These maps are available for purchase at the Cuyamaca Bookstore, or you may check out a set of maps from the library (available on reserve under my name (Chaddock: Geog. 120) for 3 hour in library use only; please do not make any marks on these maps.) You will need a pencil and a ruler to complete this assignment. Please do not hesitate to make an appointment to see me if you need any help.
This exercise is designed to further develop your map reading skills by providing an introduction to measuring latitude and longitude on topographic maps. If you want to further your skills with these maps, a more detailed treatment of topographic maps is available in Geography 121-Physical Geography Lab.
USGS topographic maps are 2-dimensional representations of the 3-dimensional Earth surface. Most cover a “quadrangle” that is bounded by parallels of latitude on the north and south edges and meridians of longitude on the west and east edges (look to map corners for latitude and longitude readings.) To refresh your memory, each degree (˚) of latitude and longitude is divisible into 60 minutes (‘), and each minute into 60 seconds (“).
Working with the Dulzura Quadrangle
The southern edge of the Dulzura Quadrangle is: 32˚ 37’30” North Latitude
9-10. Please fill in the remaining 3 map edges
Northern edge: ______
Western edge: ______
Eastern edge:______
Along the western and eastern map edges you should find additional latitude readings every 2’30”. These readings are given in minutes and seconds only. Degree readings are given only at the map corners. Example: About a third of the way down the Dulzura Quadrangle on the western and eastern edges you should see a latitude reading of 42’30”. The latitude reading at the top of the map (northern edge) is 32˚45’00” N. So the latitude reading on e third of the way down the map is 32˚42’30” N, or 2’30” south of the north edge. Using these tick marks as reference lines, please estimate to within 30” accuracy, the latitude and longitude for the following locations:
Example: Lyons Peak: 32˚42’00” N, 116˚45’45”W
11. Jamul Butte: ______
12. Honey Springs Ranch______
Working with the El Cajon Quadrangle
13. What parallel of latitude is shared by both the Dulzura Quadrangle Map and the El Cajon Quadrangle Map?______
14. What school is located at 32˚45’45” N, 116˚56’45” W? ______
Part III: Contour Line Interpolation
Topographic maps typically show elevations with contour lines—lines drawn through points of equal elevation and separated by a fixed vertical interval. Contour lines are drawn as seen from above looking straight down; they become more closely spaced as slopes become steeper. Contours do not divide, intersect, or cross; but they may merge at a vertical or overhanging cliff. Contours do not end; they always close on themselves as loops even though they may run off the edge of a map sheet before closing. Isolated closed contours appearing on the map as ellipses or circles mark the peaks of hills or the base of closed depressions. Closed depressions are differentiated by hachure lines—short ticks on the down slope side of the Contour line.
On smaller-scale maps there is less room for contours, so the contour interval will be greater than on a larger scale map of the same area. For maps of the same scale, the contour interval must be greater in areas of steeper relief—more elevation changes—to fit into the same space. Usually the contour interval for the whole quadrangle is determined by the portion with the most rugged relief. The two topographic maps we have been working on are of the same scale (1:24000), but have different elevation extremes (relief) and thus different contour intervals.
15. What is the contour interval on the El Cajon Quadrangle? ______
16. What is the contour interval on the Dulzura Quadrangle? ______
Usually, every fifth contour is drawn more heavily, and sporadically labeled with its elevation. The label is just a number; consult the map key to determine the units (feet or meters). The lighter intermediate contours are labeled only in areas of very subdued relief, were they are widely spaced. Where the intermediate contours are very widely spaced, dotted supplemental contours may be added that represent on-half the contour interval. The elevation of unlabeled contours must be determined from the nearest labeled contour and the contour interval.
Using the contour interval, interpolating where necessary, please estimate the following elevations on the El Cajon Quadrangle to within 20 feet.
Example: El Capitan High School – 420 feet
17. Riverview School:______
18. Fletcher Hills School:______
Using the contours and contour interval, interpolating where necessary, please estimate the following elevations on the Dulzura Quadrangle to within 40 feet.
Example: St. Francis Xavier Cemetery – 940 feet
19. Gasoline Curve: ______
20. Lyons Peak Lookout:______