MSL101L04 Basic Map Reading SR.pdf lesson 4.pdf

The distance east or west of a prime meridian to a

Info icon This preview shows pages 15–20. Sign up to view the full content.

Greenwich, England and is known as the Greenwich Meridian. The distance east or west of a prime meridian to a point is known as its longitude. Lines of longitude (meridians) run north- south but east-west distances are measured between them. (See Figures 4-1 and 4-2.)
Image of page 15

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

Grids 15 November 2013 TC 3-25.26 4-17 4-11. Grid coordinates divide the earth’s surface into 6-degrees-by-8-degrees quadrangles, covered with 100,000-m squares. The military grid reference of a point consists of the numbers and letters indicating where in the 100,000-m grid zone areas the point lies, plus the coordinates locating the point to the desired position within the 100,000-m square. The next step is to tie in the coordinates of the point with the larger areas. To do this, it is important to understand— Grid lines . The regularly spaced lines that make up the UTM and UPS grid on large-scale maps are divisions of the 100,000-m square. The lines are spaced at 10,000-m or 1000-m intervals. (See Figure 4-14.) Each of these lines is labeled at both ends of the map with its false easting or false northing value, showing its relation to the origin of the zone. Two digits of the values are printed in large type, and these same two digits appear at intervals along the grid lines on the face of the map. These are called the principal digits, and represent the 10,000 and 1000 digits of the grid value. They are of major importance to the map reader because they are the numbers used most often for referencing points. The smaller digits complete the UTM grid designation. Figure 4-14. Grid lines and principle digits
Image of page 16
Chapter 4 4-18 TC 3-25.26 15 November 2013 Note. As an example, the first grid line north of the south-west corner of the Columbus map is labeled 3570000m N. This means its false northing (distance north of the equator) is 3,570,000 m. The principal digits, 70, identify the line for referencing points in the northerly direction. The smaller digits, 35, are part of the false coordinates and are rarely used. The last three digits, 000, of the value are omitted. Therefore, the first grid line east of the south-west corner is labeled 689000m E. The principal digits, 89, identify the line for referencing points in the easterly direction. (See Figure 4-15.) Figure 4-15. Southwest corner of the Columbus, Georgia, map
Image of page 17

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

Grids 15 November 2013 TC 3-25.26 4-19 Grid squares. The north-south and east-west grid lines intersect at 90 degrees, forming grid squares. Normally, the size of one of these grid squares on large-scale maps is 1000 m (1 km). Grid coordinate scales. The primary tool for plotting grid coordinates is the grid coordinate scale. This scale divides the grid square more accurately than can be done by estimation and the results are more consistent. When used correctly, it presents less chance for making errors. GTA 5-2-12 contains four types of coordinate scales. (See Figure 4-16.) Figure 4-16. Coordinate scales
Image of page 18
Chapter 4 4-20 TC 3-25.26 15 November 2013 Note. The 1:50,000-scale (upper left in Figure 4-16) subdivides the 1000-m block into 10 major subdivisions, each equal to 100 m. Each 100-m block is then divided in half. Points falling between the graduations are estimated to the nearest 10 m for the fourth and eighth digits of the coordinates.
Image of page 19

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

Image of page 20
This is the end of the preview. Sign up to access the rest of the document.
  • Fall '16
  • Cartography, Geographic coordinate system, Topographic map, Universal Transverse Mercator coordinate system

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern