Lab E Introduction to Topographic Maps Examples from

Lab E – Introduction to Topographic Maps Examples from the Glendale Quadrangle, AZ

The topographic map is a valuable tool for many users and it is important to know how to read them. These maps show a tremendous amount of information, both physical and cultural. Depending on the scale, we can see individual houses, schools, small rivers, lakes, individual mountains, railroads, mining activities, agricultural areas, urban areas, etc. We will take a brief “tour” of the map to introduce you to the basic features common to all topographic maps. Let’s start with the information found around the exterior of the map and we’ll begin in the upper right corner… The map title is first…Glendale Quadrangle

Below the title is the state and county…

Below the state and county, it says 7. 5 minute series. This tells us that there are 7. 5 degrees of latitude and 7. 5 degrees of longitude shown on the map.

Now, let’s look at the bottom of the map. Starting in the lower right corner…this is the name of the map and the year in which the map was published. The map was photorevised in 1982, meaning that the map was updated from its first publication. All map features shown in purple represent those changes that took place between 1957 and 1982. When you examine the map, you’ll be able to see that it definitely needs to be revised again!

Moving to the left, we see the outline of the state of Arizona with a small black box inside. This shows you the location of this Glendale map sheet relative to the rest of the state. This illustration is especially helpful if the map you are using is from a part of the country that you are unfamiliar with.

This area at the bottom of the map shows two types of scales. There are three graphical scales in different units of measure (mile, feet, kilometer) and a scale called a representative fraction (e. g. , 1: 24000).

The top scale, the representative fraction, is read as: one inch on the map represents 24, 000 inches on the surface of the earth. You can use other units, for example, 1 cm on the map represents 24, 000 cm on the Earth’s surface. As you can see, a representative fraction is a dimensionless quantity, meaning one unit of any type on the map represents 24, 000 of the same units on earth. ßThe top scale is called a representative fraction

These are the graphical scales. They are in three different units of measure and you’ll use the one appropriate for the questions you are answering. Examine the mile scale, notice that the scale has ‘zero’ in the middle. This means that the full length of this scale is 2 miles! Be careful. The kilometer scale is then 2 km in length and the foot scale represents a distance of 8000’.

Just below the scales you will find the information regarding the contour interval for the map. The contours are the lines of constant elevation (like the isotherms and isobars that we’ve done already this semester). They are shown as brown lines on the topographic maps. The base value (datum) for these maps is sea level (zero foot elevation). This map has a contour interval of 5 feet, which means that there is a 5 foot elevation difference between adjacent contours on the map. This can be a 5 ’ difference either up or down in elevation and you will be able to determine this once you have learned to read the contours and interpret the characteristics of the terrain (Lab F).

There are three different types of contour lines: Contour lines: thin brown lines, generally without elevation markings on them. Index contours: thick brown lines with elevation values identifying them. Hachured contours: thick or thin brown lines with tick marks towards the inside of the closed contour. These indicate closed depressions. (Not shown here) On this map we can see both the contour and index contour lines. The thick index contours are every 5 th line and have reference elevations marked on them. The index contours also help to make counting lines much easier since they stand out from the others. Example, we see two index contours: 1100 and 1125. Given these two values, we can calculate the contour interval for this map (25’ difference / 5 lines = 5’). Remember, the contour interval can be read from the bottom of the map below the scales.

In the lower left corner we have the text which provides us with information on the techniques used to create the map, organization that produced it, and a key to what some of the lines and shading colors/patterns mean.

Let’s say that you need information from an adjacent map sheet, i. e. , you need to have the topographic information for the area to the NE of this Glendale map. You are in luck since the names of the adjacent maps are printed on this map. Let’s look at the NE corner of the map… The name of the map sheet you would need is the “Union Hills Quadrangle”. (You need not worry about the information above the Quad name, e. g. , 3551 II NE). There adjoining maps for all four sides and the four corners. Let’s look at the bottom of the map…

The three ovals show the locations of the names for the SW corner, SE corner, and bottom adjoining map sheets (Tolleson, Fowler, and Phoenix). I know you can’t read this, but those are the names of the respective directions.

Legend Information on Topographic Maps This information can be found in the appendix of your textbook. On these pages you will find information of what the various standard colors mean, along with the various symbols used to distinguish map features and landforms. In terms of color: Brown – contour lines and other topographic features Blue – hydrographic features (water) or glaciers Black – features constructed or designated by humans, such as buildings, roads, boundary lines, and names Green – vegetation areas such as woodlands, forests, orchards, and vineyards Red – important roads and lines of the public land survey system Gray or red tint – urban areas Purple – features added from aerial photos during map revision

DETERMINING POSITION ON THE MAP TWO BASIC TECHNIQUES • Latitude and Longitude – we worked with this in lab C, and studied it in the textbook as well as in the online topic module. • The United States Public Land Survey (USPLS) Let’s start with latitude and longitude on the topographic map…

Latitude and Longitude Latitude: These lines run east/west and are used to measure positions north or south of the equator (0°). Remember that the lines are parallel to each other hence they are also referred to as parallels. The values can be given with degrees, minutes, and seconds, followed by the ‘N’ or ‘S’ indicator. Remember that one degree is divided into 60 minutes (1°=60’) and each minute is divided into 60 seconds (1’=60”). If you think of a degree as being an hour, then the divisions seem logical. Latitude example: 34° 50’ 12”N Longitude: These lines run north/south and are used to measure positions east or west of the Prime Meridian (0°). Remember that the Prime Meridian runs from the north pole, through Greenwich, England to the south pole. These lines are also referred to as meridians. These values are given in the same format as latitude, but with a trailing ‘W’ or ‘E’ indicator. Longitude example: 129° 23’ 06”W *When giving coordinates for a location, latitude is written first, then longitude.

Let’s look across the top of the map. Below, you see the upper left and upper right portions of the map sheet. In each corner we find the latitude and longitude coordinates for each corner location. How do we tell which value of each pair is latitude and which is longitude? The red line I added is a line of latitude and it has a constant value. That is, as long as we are on this line, the value of latitude will not change, hence, the value of 33° 37’ 30” which we see at both corners is the latitude.

Longitude changes as we move east or west and you can see that the other value in each pair is changing (green highlighting). Notice that the value is increasing as we move west. Values increase from 07’ 30” to 15’ (reading right to left). Notice that this distance is 7. 5° of longitude. Are the longitudes East or West on this map sheet? To answer this, ask yourself, “where would the prime meridian be located? ”

The prime meridian represents zero longitude so it would be far to the east (right) of Glendale’s location. Therefore, all longitudes on this map (and for anywhere in the United States, would be West (west of the prime meridian). To England

The red line shows a line of longitude. Notice the value of 112° 07’ 30” is the same at the top and bottom. This is the longitude of this line. Now latitude is changing since we are moving north and south on the map. Values run from 33° 30’ to 33° 37’ 30” – again 7. 5 degrees. Now you can see why the map is called a 7. 5 minute series. It is 7. 5’ in latitude by 7. 5’ in longitude. You can see that latitude is decreasing to the south where at the equator it will be zero. Therefore, all latitudes on this map are “north”.

Besides the corners, you will find other values of latitude and longitude on the map. These are located at about 1/3 and 2/3 the way across and down the map. Other values in a different type face (font) are from a different coordinate system that you are not responsible for knowing. On this map we have the following values marked on the map for longitude… 112° 15’ 12’ 30” 10’ 112° 07’ 30” These two values are shown on the map as written here. Notice that the degree values are left off. This is done to save space. However, when you are giving latitude or longitude for a place, be sure to put them back before giving your answer!

US Public Land Survey (USPLS) The Public Land Survey System is a grid system linked to latitude and longitude and employs a rectangular grid system. This system divides the nation into a large number of standard sized units called townships and sections. This pattern is quite evident in the street grid pattern of most U. S. cities. Sites are located with reference to an east-west BASELINE and a northsouth PRINCIPAL MERIDIAN which are at right angles to each other. Both lines, like latitude and longitude, run through an initial point. The initial survey began in 1785 in the Ohio Valley. Arizona’s survey began in 1865 with the initial point for the survey being the confluence of the Gila and Salt Rivers, south of the Glendale campus near Avondale. The baseline for Arizona is Baseline Road. Once a principal meridian and baseline are drawn, a grid of lines, spaced at 6 mile intervals. The east-west lines in this grid form rows called townships. The north-south lines form columns called ranges. The intersection of rows and columns creates a pattern of boxes which are also (unfortunately) called townships. Townships are divided into 36 smaller boxes (1 mile on a side). These are called sections. Sections are numbered in a particular fashion, see the pictures that follow to demonstrate the system.

Notice how the grid is numbered. We count the number of boxes that we are either east or west of the Principal Meridian and also how many north or south of baseline. For example, look at the yellow highlighted box. The yellow township is 3 boxes to the east and 4 boxes to the north so we write Township 4 North, Range 3 East (T. 4 N. , R. 3 E. ). Each township is 6 miles on a side. 6 miles

Let’s take the highlighted township (yellow box) from the previous slide. This was Township 4 North, Range 3 East (T. 4 N. , R. 3 E. ). This, and all townships are divided into 36 sections and are numbered as shown in the upper left diagram. Section 1 is always in the upper right increasing to the left, then we drop down a row and move back to the right. This continues until we reach section 36 in the lower right. ß 36 sections = 1 township Each section is 1 mile on a side. 1 mile Now, let’s zoom in on section 14 of T. 4 N. , R. 3 E. We’ll focus on the location where the star is located.

14 One square mile (size of section) is a large area so we subdivide a section first into quarters, then smaller units as we’ll see shortly. First, we can see that the star is located in the southwest ¼ of section 14. So at this point, the proper USPLS designation for the star would be: SW¼, section 14, T. 4 N. , R. 3 E. We can subdivide the ¼ sections even further (next slide).

14 NW¼ NE¼ SW¼ SE¼ Now, we have subdivided the ¼ sections even further. Now we can express the location of the star as: NE¼, SW¼, section 14, T. 4 N. , R. 3 E.

14 NW¼ NE¼ SW¼ SE¼ You can subdivide even further…now the location is SE¼, NE¼, SW¼, section 14, T. 4 N. , R. 3 E. You can that the smaller the parcel of land you own, the longer the description is! This is the method of location commonly used by real estate as well as many cities and municipalities. We won’t go into that much detail in lab.

Let’s see what this looks like on a topographic map…in this picture you can see the division between Range 1 east and Range 2 east (R. 1 E. , R. 2 E. ). You’ll find these divisions both along the top and bottom of the map (this is the bottom). The township divisions are found along the sides (left and right) of the map. Note the section numbers, 24 is the far right section of R. 1 E. and 19 is the far left section of R. 2 E. See the diagram four slides earlier to see that this is true. Note: the downward red arrow and the words Fowler 3. 5 mi has nothing to do with the public land survey so you may ignore it. It simply is telling you that if you follow the road 3. 5 miles south, you will get to the town named Fowler.

Here you can see multiple sections and also the township boundary on the left side separating T. 2 N. from T. 3 N. This boundary is Northern Avenue. Note that section 34 (in T. 3 N. ) and section 3 (in T. 2 N. ) are not complete – we can’t see all of it. Therefore, the townships that contain these sections are NOT complete!

Here is one more example: you can see the township and range separations clearly here. Also notice that we are separating T. 1 N. and T. 1 S. – look at the name of the dividing line…it is the Base Line This map section comes from the Colorado River at Parker, AZ.

You are now finished with the lecture materials for Lab E – topographic maps. You will have another exercise dealing with reading the terrain (contours) in a couple of weeks. This is found in lab F.