Geography Reference
In-Depth Information
Exercise
1.
EXTENDED EXERCISE
Map Measurements
Overview
In this exercise you will learn techniques for measuring distance and area on maps.
An important part of making measurements is assessing their accuracy.
Objectives
Of the different ways to measure distance and area from maps, the most common
techniques use specialized instruments (an opisometer or a planimeter) or straight-
edges and grids. Accurate measures are important. A variety of processes can neg-
atively impact accuracy. The scale of the map is one such issue. Generalization may
also have impacts. Warping and stretching of paper, or imprecision in map produc-
tion, can also have more important effects. In this exercise you will learn how to
make measurements from maps and gain some insight into the results of general-
ization and other factors on the accuracy of map measurements.
Steps and Questions
For steps 1a and 1b you will need a map sheet at the scale of 1:250,000 and a map
sheet at the scale of 1:24,000 that cover the same area. If your map sheet is out of the
Public Land Survey (PLS) in the United States, skip the questions that ask for town-
ship and range information.
Find a 1:250,000 topographic sheet for an area that overlaps with the 1:24,000 topo-
graphic map sheet you get in step 1b. Also make sure that the 1:250,000 sheet
includes all the features you will need to locate in step 1b. Identify a feature (small
building, intersection, pond, etc.) on both map sheets that you will use for calculat-
ing distances.
What is the name and/or type of your feature?
What are its UTM coordinates?
With your straightedge, or paper-strip, measure the distance of this feature to
three other features:
Distance (in meters) to nearest road intersection
Distance (in meters) to highest elevation point
Distance (in meters) to nearest township/range corner
You should measure the location of the same feature you worked with first in Step 1a
feature:
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